African humid period

Short description: Holocene climate period during which northern Africa was wetter than today

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The modern, arid Sahara. The Sahara was not a desert during the African humid period. Instead, most of northern Africa was covered by grass, trees, and lakes.

The African humid period (AHP; also known by other names) was a climate period in Africa during the late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than it is today. The covering of much of the Sahara Desert by grasses, trees and lakes was caused by changes in the Earth's axial tilt, changes in vegetation and dust in the Sahara which strengthened the African monsoon, and increased greenhouse gases. During the preceding Last Glacial Maximum, the Sahara contained extensive dune fields and was mostly uninhabited. It was much larger than it is today, and its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1, simultaneously with the Bølling–Allerød warming. Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during the Younger Dryas and the short 8.2 kiloyear event. The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel, Arabia and East Africa, the end of the period appears to have taken place in several steps, such as the 4.2-kiloyear event.

The AHP led to a widespread settlement of the Sahara and the Arabian Desert, and had a profound effect on African cultures, such as the birth of the Ancient Egyptian civilization. People in the Sahara lived as hunter-gatherers and domesticated cattle, goats and sheep. They left archaeological sites and artifacts, such as one of the oldest canoes ever discovered and rock paintings such as those in the Cave of Swimmers and in the Acacus Mountains. Earlier humid periods in Africa were postulated after the discovery of these rock paintings in now-inhospitable parts of the Sahara. When the period ended, humans gradually abandoned the desert in favour of regions with more secure water supplies, such as the Nile Valley and Mesopotamia, where they gave rise to early complex societies.

## Contents

* 1 Research history
* 1.1 Research issues
* 1.2 Terminology
* 2 Background and beginning
* 2.1 Conditions before the African humid period
* 2.2 Early humidity increases
* 2.3 Onset
* 3 Causes
* 3.1 Orbital changes
* 3.2 Albedo feedbacks
* 3.3 Intertropical Convergence Zone changes
* 3.4 Precipitation changes in East Africa
* 3.5 Additional factors
* 4 Effects
* 4.1 Flora and fauna of the Sahara
* 4.2 Lakes and rivers of the Sahara
* 4.3 Humans of the Sahara
* 4.4 Additional manifestations in the Sahara
* 4.5 Arabia
* 4.6 East Africa
* 4.7 Other parts of Africa and the rainforest realm
* 4.8 Levant and Mediterranean
* 4.9 Southern Africa
* 4.10 Numerical estimates
* 4.11 Effect on other climate modes
* 4.11.1 Remote precipitation and the AHP
* 4.11.2 Hurricanes and the AHP
* 5 Fluctuations
* 6 End
* 6.1 Chronology
* 6.2 Sahara and Sahel
* 6.3 East Africa and Arabia
* 6.4 Mediterranean
* 6.5 Tropical West Africa
* 6.6 Central Africa
* 6.7 Southern Hemisphere Africa
* 6.8 Mechanisms
* 6.8.1 Potentially human-mediated changes
* 6.9 Global
* 6.10 Consequences
* 6.10.1 Humans
* 6.10.2 Non-human
* 6.10.3 Global climate
* 7 Present-day situation
* 8 Implications for future global warming
* 9 See also
* 10 Notes
* 11 References
* 11.1 Sources
* 12 Further reading

## Research history

In 1850 the researcher Heinrich Barth discussed the possibility of past climate change leading to increased wetness in the Sahara after discovering petroglyphs in the Murzuq Desert,[1] as did Ahmed Hassanein following his 1923 exploration of the Libyan Desert when he saw depictions of savanna animals at Gabal El Uweinat.[2] Further discoveries of petroglyphs led desert explorer László Almásy to coin the concept of a Green Sahara in the 1930s. Later in the 20th century, conclusive evidence of a past greener Sahara, the existence of lakes[1] and higher Nile flow levels was increasingly reported[3] and it was recognized that the Holocene featured a humid period in the Sahara.[4]

The idea that changes in Earth's orbit around the Sun influence the strength of the monsoons was already advanced in 1921, and while the original description was partly inaccurate, later widespread evidence for such orbital controls on climate was found.[1] At first it was believed that humid periods in Africa correlate with glacial stages ("pluvial hypothesis") before radiocarbon dating became widespread.[5] Beginning in the 1970s, the humidification was attributed to precessional changes.[6]

The development and existence of the African humid period has been investigated with archaeology, climate modelling and paleoproxies.[7] with archaeological sites,[8] Deposits left by wind, vegetation (e.g leaf wax), lakes and wetlands, and archaeological sites also played an important role.[9] Pollen, lake deposits and former levels of lakes have been used to study the ecosystems of the African humid period,[10] and charcoal and leaf impressions have been used to identify vegetation changes.[11] Many unresolved questions concerning the AHP remain: its beginning, cause, intensity, end, land feedbacks, and the fluctuations during the period.[12]

Recently, the hypothesized AHP end point of ~6000 years ago has been used experimentally in the Paleoclimate Modelling Intercomparison Project[13] and the effects of the Sahara's greening on other continents has drawn scientific attention.[14] The concept of a Sahara significantly different than today, and the rich record it left, has driven the imagination of the public and scientists alike.[12] It has been used as an analogue for the drying of Mars after the Amazonian-Hesperian.[15]

### Research issues

While the precipitation changes since the last glacial cycle are well established, the magnitude and timing of the changes are unclear.[16] Depending on how and where measurements and reconstructions are made, different beginning dates, ending dates, durations[3] and precipitation levels[17] have been determined for the African humid period.[3] The amounts of precipitation reconstructed from paleoclimate records and simulated by climate modelling are often inconsistent with each other;[18] in general, the simulation of the Green Sahara is considered a problem for Earth system models.[19] There is more evidence of the late phase of the AHP than its beginning.[20] Erosion of lake sediments and carbon reservoir effects make it difficult to date when they dried up.[21] Vegetation changes by themselves do not necessarily indicate precipitation changes, as changes in seasonality, plant species composition and changes in land use also play a role in vegetation changes.[22] Isotope ratios such as the hydrogen/deuterium ratio that have been used to reconstruct past precipitation values likewise are under the influence of various physical effects, which complicates their interpretation.[23] Most records of Holocene precipitation in eastern Africa come from low altitudes.[24]

### Terminology

The term "African humid period" (AHP) was coined in 2000 by Peter B. de Menocal et al.[25] Earlier humid periods are sometimes known as "African humid periods"[26] and a number of dry/wet periods have been defined for the Central Africa region.[27] In general, these types of climate fluctuations between wetter and drier periods are known as "pluvials" and "interpluvials", respectively.[28] The term "Green Sahara" is frequently used to describe the AHPs.[29] Because the AHP did not affect all of Africa, some scientists have instead used and recommended "North African humid period" and "Northern African humid period".[30]

Other terms that have been applied to the Holocene AHP or correlative climate phases are "Holocene humid period", which also covers an analogous episode in Arabia and Asia;[31] "Early Holocene Humid Period";[32] "early to mid-Holocene humid episode";[33] "African Holocene Humid Period" (AHHP);[34] " "Holocene Pluvial";[35] "Holocene Wet Phase";[36] "Kibangien A" in Central Africa;[37] "Makalian" for the Neolithic period of northern Sudan;[38] "Nabtian Pluvial",[39] "Nabtian Wet Phase"[40] or "Nabtian period" for the 14,000–6,000 humid period over the Eastern Mediterranean and Levant;[41] "Neolithic pluvial";[42] "Neolithic Subpluvial";[36] "Neolithic wet phase";[43] "Nouakchottien" of the Western Sahara 6,500 – 4,000 years before present;[44] "Subpluvial II"[43] and "Tchadien" in the Central Sahara 14,000 – 7,500 years before present.[44] The terms "Big Dry",[45] "Léopoldvillien"[46] and Ogolien (fr) have been applied to the dry period in the Last Glacial Maximum,[47] the latter is equivalent to the "Kanemian";[48] "Kanemian dry period" refers to a dry period between 20,000 and 13,000 years before present in the Lake Chad area.[49]

## Background and beginning

The African humid period took place in the late Pleistocene[50] and early-middle Holocene,[51] and saw increased precipitation in Northern and Western Africa due to a northward migration of the tropical rainbelt.[22] The AHP stands out within the otherwise relatively climatically stable Holocene.[52][53] It is part of the so-called Holocene climatic optimum[54] and coincides with a global warm phase, the Holocene Thermal Maximum.[55][lower-alpha 1] Liu et al. 2017[57] subdivided the humid period into an "AHP I" which lasted until 8,000 years ago, and an "AHP II" from 8,000 years onward,[58] with the former being wetter than the latter.[59]

The African humid period was not the first such phase; some evidence exists for as many as 230 older such "green Sahara"/wet periods going back perhaps to the first appearance of the Sahara 7–8 million years ago.[1] Earlier humid periods appear to have been more intense than the AHP of the Holocene,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". including the exceptionally intense Eemian humid period. This humid period provided the pathways for early humans to cross Arabia and Northern AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and which, together with later moist periods, has been linked to expansions of the Aterian populationsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the speciation of insect species.[60] Such humid periods are usually associated with interglacials, while glacial stages correlate to dry periods;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". they occur during precession minima, unless large ice sheets or insufficient greenhouse gas concentrations suppress their onset.[61]

The Bølling–Allerød warming appears to be synchronous with the onset of the African humid periodLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as well as to increased humidity in Arabia.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Later, in the Blytt–Sernander sequence the humid period coincides with the Atlantic period.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Conditions before the African humid period

African vegetation during the last glacial maximum

During the Last Glacial Maximum, the Sahara and Sahel had been extremely dry.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The extent of dune sheets and water levels in closed lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". indicate that less precipitation fell than today.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Sahara was much larger,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". extending Lua error: Internal error: The interpreter has terminated with signal "24". farther southLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". to about 12° northern latitude. Dunes were active much closer to the equator,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".[lower-alpha 2] and rainforests had retreated in favour of afromontane and savannah landscapes as temperatures, rainfall, and humidity decreased.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

There is little and often equivocal evidence of human activity in the SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or Arabia at that time, reflecting their drier nature;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in the Acacus Mountains the last human presence was recorded 70,000–61,000 years ago, and by then the LGM humans had largely retreated to the Mediterranean coast and the Nile Valley.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The aridity during the Last Glacial Maximum appears to have been the consequence of the colder climate and larger polar ice sheets, which squeezed the monsoon belt to the equator and weakened the West African Monsoon. The atmospheric water cycle and the Walker and Hadley circulations were weaker as well.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Exceptional dry phases are linked to Heinrich events[lower-alpha 3]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". when there are a large number of icebergs in the North Atlantic;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the discharge of large amounts of such icebergs between 11,500 and 21,000 years before present coincided with droughts in the subtropics.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Before the onset of the AHP, it is thought that Lake Victoria, Lake Albert, Lake Edward,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake TurkanaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Sudd swamps had dried out.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The White Nile had become a seasonal riverLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". whose courseLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". along with that of the main Nile may have been dammed by dunes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Nile Delta was partially dry, with sandy plains extending between ephemeral channels and exposed seafloor, and it became a source of sand for ergs[lower-alpha 4] farther east.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Other lakes across Africa, such as Lake Chad and Lake Tanganyika, also had shrunk[lower-alpha 5] during this time,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and both the Niger River and Senegal River were stunted.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Early humidity increases

Whether some parts of the desert such as highlands like the Red Sea Hills were reached by the westerliesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or weather systems associated with the subtropical jet streamLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".—and thus received precipitation—is contentious. It is only clearly supported for the Maghreb in northwestern AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and parts of northeastern Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". though river flowLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24"./terrace formationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and lake development in the Tibesti and Jebel Marra mountains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Residual Nile flow may be explained in this way.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The highlands of Africa appear to have been less affected by drought during the last glacial maximum.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The end of the glacial drought occurred between 17,000 and 11,000 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with an earlier beginning noted in the Acacus,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". SinaiLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Saharan mountainsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". 26,500–22,500Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and (possibly) 18,500 years ago, respectively.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In southernLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and central Africa earlier starts 17,000 and 17,500 years ago, respectively, may be linked to Antarctic warming,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while Lake Malawi appears to have been low until about 10,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

High lake levels occurred in the Jebel Marra and Tibesti Mountains between 15,000 and 14,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the youngest stage of glaciation in the High Atlas mountains took place at the same time as the Younger Dryas and early African humid period.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Around 14,500 years ago, lakes started to appear in the arid areas.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Onset

The humid period began about 15,000Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".–14,500 years ago.[lower-alpha 6]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The onset of the humid period took place almost simultaneously over all of Northern[lower-alpha 7] and Tropical Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with impacts as far as Santo Antão on Cape Verde.[62] Wet conditions apparently took about oneLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". to two millenniaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". to advance northward in the SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Arabia,[lower-alpha 8] respectively.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The terrestrial system (e.g groundwater bodies) took time to respond to changed conditions.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Lake Victoria reappeared and overflowed;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake Albert also overflowed into the White NileLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". 15,000–14,500 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and so did Lake Tana, into the Blue Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The White Nile flooded part of its valleyLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and reconnected to the main Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".[lower-alpha 9] In Egypt widespread flooding by the "Wild Nile" took place;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". this "Wild Nile" periodLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". led to the largest recorded floods on this riverLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and sedimentation in floodplains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Even earlier, 17,000–16,800 years ago, meltwater from glaciers in Ethiopia – which were retreating at that time – may have begun to increase the flow of water and sediment in the Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the East African Rift water levels in lakes began to rise by about 15,500/15,000Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".-12,000 years ago;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake Kivu began overflowing into Lake Tanganyika by about 10,500 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

About the same time that the AHP started, the cold glacial climate in Europe associated with Heinrich event 1 endedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with climate changing as far as Australasia.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A warming and retreat of sea ice around Antarctica coincides with the start of the African humid period,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although the Antarctic Cold Reversal also falls into this timeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and may relate to a drought interval recorded in the Gulf of Guinea.[64]

## Causes

The African humid period was caused by a stronger West African MonsoonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". directed by changes in solar irradiance and in albedo feedbacks.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". These led to increased moisture import from both the equatorial Atlantic into West Africa, as well as from the North Atlantic and the Mediterranean Sea towards the Mediterranean coasts of AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Tibesti Mountains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There were complex interactions with the atmospheric circulation of the extratropics and between moisture coming from the Atlantic Ocean and the Indian Ocean,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and an increased overlap between the areas wetted by the monsoon and those wetted by extratropical cyclones.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Climate models indicate that changes from a dry to a "green" Sahara and back have threshold behaviour, with the change occurring once a certain level of insolation is exceeded;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". likewise, a gradual drop of insolation often leads to a sudden transition back to a dry Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This is due to various feedback processes which are at work,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in climate models there is often more than one stable climate-vegetation state.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Sea surface temperature and greenhouse gas changes synchronized the beginning of the AHP across Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Orbital changes

Milankovich cycles over the past one million years

The African humid period has been explained by increased insolation during Northern Hemisphere summer.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Due to precession, the season at which Earth passes closest to the Sun on its elliptical orbit – the perihelion – changes, with maximum summer insolation occurring when this happens during Northern Hemisphere summer.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Between 11,000 and 10,000 years ago, Earth passed through the perihelion at the time of summer solstice, increasing the amount of solar radiation by about 8%,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". resulting in the African monsoon becoming both stronger and reaching farther north.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Between 15,000 and 5,000 years ago, summer insolation was at least 4% higher than today.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The obliquity also decreased during the HoloceneLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but the effect of obliquity changes on the climate is focused on the high latitudes and its influence on the monsoon is unclear.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

During summer, solar heating is stronger over the North African land than over the ocean, forming a low pressure area that draws moist air and precipitation inLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". from the Atlantic Ocean.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This effect was strengthened by the increased summer insolation,[65] leading to a stronger monsoon that also reached farther north.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The effects of these circulation changes reached as far as the subtropics.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Obliquity and precession are responsible for two of the foremost Milankovich cycles and are responsible not only for the onset and cessation of ice agesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but also for monsoon strength variations.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Southern Hemisphere monsoons are expected to have the opposite response of Northern Hemisphere monsoons to precession, as the insolation changes are reversed; this observation is borne out by data from South America.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The precession change increased seasonality in the Northern Hemisphere while decreasing it in the Southern Hemisphere.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Albedo feedbacks

Lua error: Internal error: The interpreter has terminated with signal "24".

According to climate modelling,[1] orbital changes by themselves cannot increase precipitation over Africa enough to explain the formation of the large desert lakes such as Lua error: Internal error: The interpreter has terminated with signal "24". Lake Megachad,[lower-alpha 10]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the climate proxies for precipitation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or the northward expansion of vegetationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". unless ocean and land surface changes are factored in.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Decreasing albedo resulting from vegetation changes is an important factor in the precipitation increase.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Specifically, increased precipitation increases the amount of vegetation; vegetation absorbs more sunlight and thus more energy is available for the monsoon. In addition, evapotranspiration from vegetation adds more moisture, although this effect is less pronounced than the albedo effect.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Heat fluxes in the soil and evaporation are also altered by the vegetation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Reduced dust generation from a wetter Sahara,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where major dust-generating regions were submerged by lakes, influences the climateLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". by reducing the amount of light absorbed by dust.[1] Decreased dust emissions also modify cloud properties, making them less reflective and more efficient at inducing precipitation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In climate models, reduced amounts of dust in the troposphere together with vegetation changes canLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". often but not always explain the northward expansion of the monsoon.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There is not universal agreement on the effects of dust on precipitation in the Sahel, however,[1] in part because the effects of dust on precipitation may be dependent on its size.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

In addition to raw precipitation changes, changes in precipitation seasonality such as the length of dry seasons need to be considered when assessing the effects of climate change on vegetation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as well as the fertilizing effects of increased carbon dioxide concentrations in the atmosphere.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Other sources of albedo changes:

* Changes in soil properties result in changes in the monsoon; replacing desert soils with loamy ones results in increased precipitation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and soils that are wetLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or contain organic matter reflect less sunlight and accelerate the moistening process.[1] Desert sand changes also modify the albedo.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Albedo changes caused by lakes and wetlandsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". can alter precipitation in climate models.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Intertropical Convergence Zone changes

Warmer extratropics during summer may have drawn the Intertropical Convergence Zone (ITCZ) northwardLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". by about five or seven degrees latitude,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". resulting in precipitation changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Sea surface temperatures off North Africa warmed under orbital effects and through weaker trade winds, leading to a northward movement of the ITCZ and increasing moisture gradients between land and sea.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Two temperature gradients, one between a cooler Atlantic during spring and an already warming African continent, the other between warmer temperatures north of 10° latitude and cooler south, may have assisted in this change.[66] In Eastern Africa, ITCZ changes had relatively little effect on precipitation changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The past position of the ITCZ in Arabia is also contentious.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Precipitation changes in East Africa

The African humid period that took place in East Africa appears to have been caused by different mechanisms.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Among the proposed mechanisms are decreased seasonality of precipitationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". due to increased dry season precipitation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". shortening of the dry season, increased precipitationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased inflow of moisture from the Atlantic and Indian Oceans. The Atlantic moisture inflow was in part triggered by a stronger West African and Indian monsoon, perhaps explaining why the effects of the AHP extended into the Southern Hemisphere.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".The behaviour of the easterly trade winds is unclear; increased moisture transport by easterly trade winds may have aided in the development of the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but alternatively a stronger Indian Monsoon that draws easterly winds away from East Africa may have occurred.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Changes in the Congo Air Boundary[lower-alpha 11]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or increased convergence along this boundary may have contributed;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the Congo Air Boundary would have been shifted east by the stronger westerly windsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". directed by lower atmospheric pressure over Northern Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". allowing additional moisture from the Atlantic to reach East Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The parts of East Africa that were isolated from Atlantic moisture did not become significantly wetter during the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although at one site in Somalia the seasonality of precipitation mayLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or may not have decreased.[67]

Various contributing factors may have led to the increased humidity in East Africa, not all of which were necessarily operating simultaneously during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Finally, increased greenhouse gas concentrations may have been involved in directing the onset of the AHP in tropical southeastern Africa;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". there, orbital changes would be expected to lead to climate variations opposite to those in the Northern Hemisphere.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The pattern of humidity changes in south-eastern Africa are complex.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Additional factors

* Climate change in the far northern latitudes may have contributed to the onset of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The shrinkage of the Scandinavian and the Laurentide Ice Sheets occurred at its beginning,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in climate models, a retreat of the ice sheets is often required to simulate the humid periodLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although their size has little influence on its intensity.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Their existence might also explain why the AHP did not start immediately with the early insolation peak, as still existing ice sheets would have cooled the climate.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Sea surface temperature changes in the Atlantic influence the African monsoonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and may have influenced the onset of the AHP. Weaker trade winds and higher insolation would lead to warmer sea surface temperatures, increasing precipitation by increasing land-sea moisture gradientsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and evaporation rates.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Changes in the Atlantic meridional overturning circulation (AMOC)Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and North Atlantic temperature gradients were also involved.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Warming of the Mediterranean Sea increases the amount of Sahel precipitation; this effect is responsible for the recent anthropogenic global warming mediated increase in Sahel precipitation.[1] Warmer sea surface temperatures there might also explain the increased precipitation recorded in the MediterraneanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased intensity of precipitation reconstructed from former rivers in the Sahara during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Increased precipitation during winter is correlated with a larger spatial extent of Mediterranean precipitation and might have aided in the establishment of the AHP in North Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". particularly Algeria,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Morocco,[68] Northern Egypt,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the northern Red Sea,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the Tibesti,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". northern Arabia,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and generally at higher latitudes where the monsoon did not arrive[66] or may have been inadequate.[69] This precipitation may have extended to other parts of the Sahara; such would have led to the areas of summer and winter precipitation overlappingLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the dry area between the monsoonal and westerlies-influenced climate zones becoming wetter or disappearing altogether.[70] Such changes in Mediterranean-derived precipitation may correlate with changes in the North Atlantic and Arctic OscillationsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and with the increased contrast between warm summers and cold winters,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and may be driven by orbital changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some studies however see a decrease in winter precipitation in northwestern Africa due to a poleward shift of the storm tracks.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Trough-mediated northward transport of moisture during autumn and spring has also been proposed to explain the increased precipitation and its underestimation by climate models.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased northward moisture transport by such troughs increases autumn rainfall in the Sahara when the ITCZ is shifted north and thus its moisture can be more easily captured by troughs, generating moisture plumes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This mechanism is particularly relevant to the northwestern Sahara south of the Atlas Mountains where the monsoon proper might not have reached,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and may also be relevant to northern Arabia.[71]
* Weaker subtropical anticyclones were proposed as an explanation during the 1970s–1980s.[72]
* In montane regions such as the Meidob volcanic field cold temperatures after the last glacial maximum may have reduced evaporation and thus allowed an early onset of humidity.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Changes in the Earth's geomagnetic field may be linked to the humidity changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Increased moisture supply from dispersed lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and larger lakes like Lake Megachad may have increased the precipitation, although this effect is probably not adequate to explain the entire AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and model-dependent.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A similar role has been attributed to the extensive wetlands, drainages and lakes in the Eastern SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and to the ecosystem in general.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Two high elevation winds, the African Easterly Jet and the Tropical Easterly Jet modulate atmospheric air flows over Africa and thus also the amount of precipitation; the Tropical Easterly Jet comes from India and is powered by temperature gradients between the tropicsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the subtropics while the African Easterly Jet is powered by temperature gradients in the Sahel.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A stronger West African Monsoon resulted in a weaker African Easterly Jet and thus decreased transport of moisture out of Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Increased atmospheric carbon dioxide concentrations may have played a role in triggering the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". especially its extension across the equator,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as well as its resumption after the Younger Dryas and Heinrich event 1 through increased sea surface temperatures.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Carbon dioxide concentrations have a strong influence on the intensity of orbital changes needed to start an AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but do not play a major role in controlling its intensity.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* In some parts of the Sahara increased water supply from montane regions may have assisted in the development of moist conditions.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Larger forests in Eurasia may have led to a northward shift of the ITCZ.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Along the coast of Senegal, sea level rise helped the establishment of the AHP vegetation.[73]
* Other proposed mechanisms involve convection occurring above the atmospheric boundary layer,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". increased latent heat fluxes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". changes in tropical wave activity over Africa,[74] low pressure in northwestern Africa drawing moisture into the Sahara,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". stronger Asian monsoons drawing Indian Ocean moisture to Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". increased runoff due to changes in the precipitation regime rather than precipitation quantity,[69] changes in the Red Sea Trough[lower-alpha 12] (for Arabia),[71] changes in the solar cyclesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and complex atmospheric flow phenomena.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

## Effects

Vegetation and water bodies in the Eemian (bottom) and Holocene (top)

The African humid period extended over most of Africa:Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Sahara and eastern,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". southeastern and equatorial Africa. In general, forests and woodlands expanded through the continent.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A similar wet episode took place in the tropical Americas[lower-alpha 13] and Asia,[lower-alpha 14]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". including the Makran region,[78] the Middle EastLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Arabian Peninsula;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the episode appears to relate to the same orbital forcing as the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". An early Holocene monsoonal episode extended as far as the Mojave Desert in North America.[79] In contrast, a drier episode is recorded from much of South America where Lake Titicaca, Lake Junin, the discharge of the Amazon River and water availability in the Atacama were lower.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The discharge of the Congo, Niger,[80] Nile,[81] Ntem,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Rufiji,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Sanaga rivers increased.[80] Runoff from Algeria,[82] equatorial Africa, northeastern Africa and the western Sahara was also larger.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased discharge led to changes in the morphology of the river systems and their alluvial plains,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Senegal River expanded its riverbed,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". breached dunes and re-entered the Atlantic Ocean.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Flora and fauna of the Sahara

During the African humid period, lakes, rivers, wetlands and vegetation including grass and trees covered the SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Sahel,[65] creating a "Green Sahara"Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with a land cover that has no modern analogues.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Evidence includes pollen data, archaeological sites, evidence of faunal activity such as diatoms, mammals, ostracods, reptiles and snails, buried river valleys, organic-rich mats, mudstones, evaporites as well as travertines and tufas deposited in subaqueous environments.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

A present-day savannah, Tarangire National Park, Tanzania

The vegetation cover then extended over almost all of the SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and consisted of an open grass savannah with shrubs and trees,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with a moist savanna vegetation getting established in the mountains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In general, the vegetation expanded northwardLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". to 27–30° northern latitude in West AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with a Sahel boundary at about 23° north,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as the Sahara was populated by plants that today often occur about Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".-Lua error: Internal error: The interpreter has terminated with signal "24". farther south.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The northward movement of vegetation took some time and some plant species moved faster than others.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Plants that perform C3 carbon fixation became more common.[83] The fire regime has important effects on the vegetation and fauna;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". during the AHP, with some northern areas becoming wet enough that vegetation could sustain burns, and more southern areas becoming too wet.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Forests and plants from the humid tropics were concentrated around lakes, riversLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Atlantic Ocean coast of Senegal;[84] waterbodies were also settled by aquatic and partially aquatic plantsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Senegalese coast by mangroves.[73] The landscape during the AHP has been described as a mosaic between various vegetation types of semi-desert, humidLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or tropical originLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". rather than a simple northward displacement of plant species,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There was no southward displacement of Mediterranean plants during the HoloceneLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and on the Tibesti Mountains cold temperatures may have restricted the expansion of tropical plants.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Pollen data often show a dominance of grasses over humid tropics trees.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The tree Lophira alata and others may have spread out of the African forests during the AHP,[85] and the Lactuca plants may have split into two species under the effects of the AHP and other climate changes in Africa during the Holocene.[86]

The Sahara climate did not become entirely homogeneous; its central-eastern parts were probably drier than the western and central sectorsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Libyan sand sea was still a desert[1] although pure desert areas retreated to small core areasLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or became arid/semiarid.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". An arid belt may have existed north of 22° latitudeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and towards the Nile Delta,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or the vegetationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the African monsoon might have reached 28–31° northern latitude;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in general conditions between 21° and 28° northern latitude are poorly known.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Dry areas may have persisted in the rain shadows of mountains and could have supported arid climate vegetation, explaining the presence of its pollen in sediment cores.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In addition, north–south gradations in vegetation patterns have been reconstructed from charcoal and pollen data.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Fossils record changes in the animal fauna of the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This fauna included antelopes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". baboons,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". birds,[87] cane rats,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". catfish,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". clams,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". cormorants,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". crocodiles,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". elephants,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". frogs,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". gazelles,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". giraffes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". hartebeest,[88] hares,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". hippopotamuses,[88] molluscs, Nile perches,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". pelicans,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". rhinoceroses,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". snake-eagles,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". snakes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". tilapia,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". toads,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". turtlesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and many more animals,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in Egypt there were African buffaloes, spotted hyenas, warthogs, wildebeest and zebra.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Additional birds include brown-necked raven, coot, common moorhen, crested grebe, glossy ibis, long-legged buzzard, rock dove, spur-winged goose and tufted duck.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some migratory birds may have changed their flying route in response to the AHP.[89] Large herds of animals lived in the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some animals expanded over the whole desert, while others were limited to places with deep water.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Humid periods in the Sahara may have allowed species to cross the now-desert.[90]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A reduction in open grasslands at the beginning of the AHP may explain the decline of the populations of some mammals during[91] and a population bottleneck in cheetahs at the start of the humid period,[92] while leading to the expansion of the population of other animals such as Hubert's multimammate mouse[93] and Natal multimammate mouse.[94]

### Lakes and rivers of the Sahara

Lake Megachad, with present-day Lake Chad highlighted in green

A number of lakes formedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or expanded in the Sahara[72] and the Hoggar and Tibesti Mountains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The largest of them was Lake Chad which increased to at least ten times its present-day sizeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". to form Lake MegachadLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or Megalake Chad, then the largest lake on Earth.[95] This enlarged Lake Chad reached dimensions of Lua error: Internal error: The interpreter has terminated with signal "24". in north–south and east–west direction respectively,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". covering the Bodélé DepressionLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and perhaps as much as 8% of the present-day Sahara desert.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". It influenced the climate itself;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". for example rainfall would have been reduced at the centre of the lake and increased at its margins.[1] Lake Chad was possibly fed from the north by rivers draining the Hoggar (Taffassasset drainage)Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Tibesti Mountains, from the Ennedi Mountains in the east through the "Eastern palaeorivers"[96] and from the south by the Chari-Logone and Komadugu Rivers.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Chari River was the main tributaryLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while the rivers draining the Tibesti formed alluvial fansLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24"./the Angamma river delta at their entry into northern Lake Chad.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Skeletons of elephants, hippos and hominins have been found in the Angamma delta, which is the dominant shoreline feature of northern Lake Chad.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The lake overflowed into the Niger RiverLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". during highstand through the Mayo Kebbi and the Benue River, eventually reaching the Gulf of Guinea.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Older dune systems were submerged by Lake Chad.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Among the largeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". lakes which may have formed in the Sahara are Lake Megafezzan in LibyaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Lake Ptolemy in Sudan.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Quade et al. 2018 raised some doubts about the size and existence of some of these lakes such as Lake Ptolemy, Lake Megafezzan, Lake Ahnet-Mouydir;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". it is possible that giant lakes only formed in the southern part of the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Other lakes are known from Adrar Bous in Niger,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Era Kohor and Trou au Natron in the Tibesti Mountains,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". I-n-Atei in the Hoggar, at Ine SakaneLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in Taoudenni in Mali,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the Garat Ouda and Takarkori Lakes in the Acacus Mountains,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Chemchane in Mauretania,[97] at Guern El Louläilet in the Great Western Erg,[98] and Hassi el Mejnah and Sebkha Mellala both in Algeria,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". at Wadi Shati and elsewhere in the Fezzan in Libya,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". at Bilma, Dibella, FachiLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Gobero in the Ténéré,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lua error: Internal error: The interpreter has terminated with signal "24". in NigerLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and at "Eight Ridges",Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". El Atrun,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake Gureinat, Merga,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". "Ridge",Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Sidigh,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Wadi Mansurab,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Selima and Oyo in Sudan.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The lakes of Ounianga merged into two large lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and overflowed, either above surface or underground.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Mosaics of small lakes developed in some regions,[99] such as the Grand Erg Occidental.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Wetlands also expanded during the AHP, but both their expansion and subsequent retreat were slower than that of lakes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Saharan topography prevents rapid drainage of accumulated water, thus favouring the development of waterbodies.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Niger River, which had been dammed by dunes during the LGM, formed a lake in the Timbuktu region that eventually overflowed and drained at some point during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

In some parts of the Sahara ephemeral lakes formed such as at Abu Ballas, Bir Kiseiba,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Bir Sahara, Bir Tarfawi and Nabta Playa[lower-alpha 15] in Egypt,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which may relate to later Egyptian religions,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or swamp-lakes such as at Adrar Bous close to the Air Mountains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Ephemeral lakes developed between dunes,[100] and a "freshwater archipelago" appears to have existed in the Murzuq basin.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". All these lake systems left fossils such as fish, limnic sedimentsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and fertile soils that were later used for agriculture (El Deir, Kharga Oasis).Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Finally, crater lakes formed in volcanic fields[101] such as Trou au Natron and Era Kohor in the Tibesti,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and sometimes survive to this day as smaller remnant lakes such as Malha craterLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in the Meidob volcanic field.[101] Potentially, the increased availability of water during the AHP may have facilitated the onset of phreatomagmatic eruptions such as maar formation in the Bayuda volcanic field, although the chronology of volcanic eruptions there is not well known enough to substantiate a link to the AHP.[102]

Increased precipitation resulted in the formation or reactivation of river systems in the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The large Tamanrasset River[103] flowed from the Atlas Mountains and Hoggar westward towards the AtlanticLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and entered it in the Bay of Arguin in Mauritania.[104] It once formed the 12th largest watershed in the world[105] and left a submarine canyon and riverine sediments.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Together with other rivers it formed estuaries and mangroves in the Bay of Arguin.[104] Other rivers in the same area also formed submarine canyons,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and sediment patterns in marine sediment coresLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the occurrence of submarine landslides in the area have been related to the activity of these rivers.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Rivers such as the Irharhar in Algeria, Libya and TunisiaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Sahabi and Kufra rivers in Libya were active during this timeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although there is some doubt that they had perennial flowLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or that they reached the sea directly;[106] they appear to have been more important in earlier humid periods.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Small watersheds,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". wadisLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and rivers discharging into endorheic basins such as Wadi Tanezzuft also carried water during the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". leading to increased erosion.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Egypt, some rivers active during the AHP are now gravel ridges.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Air, Hoggar and Tibesti Mountains, the so-called "Middle Terrace" was emplaced at this time.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The rivers[lower-alpha 16] and lakes of the Sahara may have acted as pathways for the spread of humans and animals;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". animals that might have propagated through the Sahara in these waterbodies are Nile crocodile and the fish Clarias gariepinus and Tilapia zillii.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The name Tassili n'Ajjer, which means "plateau of the rivers" in Berber, may be a reference to past river flows.[107] On the other hand, intense flows of these rivers may have made their shores dangerous to humans and thus created additional impetus for human movement.[108] Now-dry river valleys from the AHP in the eastern Sahara have been used as analogues for former river systems on Mars.[109]

### Humans of the Sahara

Conditions and resources were ripe for first hunter-gatherers, fishermenLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and, later, pastoralists;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the exact chronology – when humans returned in the Sahara after the onset of the AHP – is disputed.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". They may have come either from the north (Maghreb or Cyrenaica)Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where the Capsian culture[lower-alpha 17] was located,[110] the south (Sub-Saharan Africa), or the east (Nile Valley).Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The human population in the Sahara rapidly increased during the AHP, interrupted by a brief decline between 7,600 and 6,700 years ago.[111] Traces of human activity have been found in the Acacus MountainsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where caves and rock shelters were used as basecamps for humans,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as the Uan Afuda caveLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Uan Tabu and Takarkori rock shelters.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The first occupation in Takarkori took place between 10,000 and 9,000 years ago;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". about five millennia of human cultural evolution are recorded there.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". At Gobero in the Ténéré desert a cemetery has been found, which has been used to reconstruct the lifestyle of these former inhabitants of the Sahara,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and at Lake Ptolemy in Nubia humans settled close to the lake shore, using its resources and perhaps even engaging in leisure activities.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". At that time, many humans appear to have depended on water-bound resources, seeing as many of the tools left by the early humans are associated with fishery; hence this culture is also known as "aqualithic"Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although substantial differences between the cultures of various places have been found.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The greening of the Sahara led to a demographic expansion[112] and especially in the Eastern Sahara human occupancy coincides with the AHP.[113] Conversely occupation decreased along the Nile valley,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as it became inhospitable to human settlement due to flooding[114] extending to the Nile delta.[115] Humans moved into the Sudanese segment of the Nile valley only by about 11,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Humans were hunting large animals with weapons that have been found in archaeological sitesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and wild cereals occurring in the Sahara during the AHP such as brachiaria, sorghum and urochloa were an additional source of food.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Humans also domesticated cattle,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". goats and sheep.[116] Cattle domestication may have occurred especially in the more environmentally variable Eastern Sahara,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where the lack of lakes (cattle having high requirements of drinking water) may however have limited the occurrence of cattle.[117] Animal husbandry picked up in earnest around 7,000 years ago when domestic animals came to the Sahara, and a population boom may be linked to this change in cultural practice;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". cattle and goats spread southwestwards from northeasternmost Africa from 8,000 years before present.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Dairying has been demonstrated in some locationsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and cattle-husbandry is supported by the frequent depiction of cattle in rock paintings.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The relative importance of hunter-gatherer practices and pastoralism, and whether people were sedentary or migratory, is unclear.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Dufuna canoe, one of the oldest known ships in the world,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". appears to date to the Holocene humid period and implies that the waterbodies of that time were navigated by humans.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The cultural units "Masara" and "Bashendi" existed in Dakhleh Oasis during the AHP.[118] In the Acacus Mountains, several cultural horizons known as Early and Late Acacus and Early, Middle, Late and Final Pastoral have been identifiedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while in Niger the Kiffian culture has been related to the beginning of the AHP.[119] Ancient civilizations thrived,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with farming and animal husbandry taking place in Neolithic settlements.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Possibly, the domestication of plants in Africa was delayed by the increased food availability during the AHP, it only took place around 2,500 BC.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Images of swimming people in the Cave of Swimmers

Humans created rock art such as petroglyphs and rock paintings in the Sahara, perhaps the largest density of such creations in the world.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Scenes include animalsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and everyday lifeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as swimming which supports the presence of past wetter climates.[102] One well-known such petroglyph location is the Cave of Swimmers in the Gilf Kebir mountains of Egypt;[120] other well known sites are the Gabal El Uweinat mountains also of Egypt,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". ArabiaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Tassili n'Ajjer in Algeria where rock paintings from this time have been discovered.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Humans also left artifacts such as Fesselsteine[lower-alpha 18] and ceramics in what today are inhospitable deserts.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". North Africa together with East Asia is one of the first places where pottery was developedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". probably under the influence of increased availability of resources during the AHP. The humid period also favoured its development and spread in West Africa during the 10th millennium BC;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the so-called "wavy line" or "dotted wavy-line" motif was widespread across Northern AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and as far as Lake Turkana.[121] A similar but more circumscribed spread occurred with the Ounan arrow points.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

These populations have been described as Epipaleolithic, Mesolithic and NeolithicLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and produced a variety of lithic tools and other assemblages.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In West Africa, the cultural change from the African Middle Stone Age to the Late Stone Age accompanied the beginning of the AHP.[122] In Sudan, the beginning of the early Khartoum culture coincides with the initiation of the AHP.[123] Genetic and archaeological data indicate that these populations which exploited the resources of the AHP Sahara probably originated in Sub-Saharan Africa and moved north after some time, after the desert got wetter;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in return, the AHP facilitated the movement of some Eurasian populations into Africa,[124] and bidirectional travel across the Sahara more generally.[125] The northward spread of Macrohaplogroup L and Haplogroup U6 genomic lineages may reflect this tendency[126] but did not result in widespread genetic exchanges between Northern and sub-Saharan Africa.[127] Elsewhere, newly formed or expanded water courses may have restricted human mobility and isolated populations.[128] These favourable conditions for human populations may be reflected in paradise myths such as the Garden of Eden in The Bible and Elysium and the Golden Age in Classical Antiquity,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while a possible role in the development of the Afroasiatic[129] and the spread of the Niger-CongoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Nilo-Saharan languagesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". is debatable.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". References in Egyptian chronicles about moist lands along the Red Sea may record the wet conditions of the late AHP.[130]

### Additional manifestations in the Sahara

The expanded vegetation and soil formation stabilized previously active dunes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". eventually giving rise to the present-day draa dunes in the Great Sand Sea of Egypt for example,[100] although there is uncertainty about whether this stabilization was widespread.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Soil development and biological activity in soils are attested in the Acacus MountainsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Mesak Settafet area of Libya,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but evidence of soil formationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24"./pedogenesisLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as bog ironLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or kaolinite formation are described from other parts of the Sahara and Sahel as well.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".[131] In the Selima Sand Sheet, the landscape underwent erosional truncation and bioturbation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Erosion by increased runoff delayed soil development until after a few millennia after the onset of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Central and Southern Sahara saw the development of alluvial deposits[72] while sebkha deposits are known from the Western Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lightning strikes into soil left lightning-altered rocks in parts of the Central Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The Lakes of Ounianga are recharged from fossil groundwater that originated partly during the AHP

The increased precipitation recharged aquifersLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as the Nubian Sandstone Aquifer; presently, water from this aquifer maintains several lakes in the Sahara, such as the Lakes of Ounianga.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Other groundwater systems were active at that time in the Acacus Mountains, Air Mountains, in the FezzanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and elsewhere in LibyaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Sahel.[132] Raised groundwater tables provided water to plants and was discharged in depressions,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". lakes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". springsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and valleys, forming widespread carbonate deposits[lower-alpha 19] and feeding lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and wetlands.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The formation of lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and vegetation reduced the export of dust from the Sahara. This has been recorded in marine cores,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". including one core where dust export decreased by almost half,[133] and in Italian lakes.[134] In coastal places, such as in Oman, sea level rise also reduced the production of dust.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Mediterranean, a decreased dust supply was accompanied by increased sediment input from the Nile, leading to changes in marine sediment composition.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Conversely, the increased vegetation may have yielded more volatile organic compounds in the air.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Whether the strengthening of the monsoon enhanced or reduced upwelling off Northwestern Africa is debatable,[135] with some research suggesting that the strengthening in upwelling decreased sea surface temperaturesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased the biological productivity of the sea,[135] while other research suggests that the opposite occurred; less upwelling with more moisture.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". However, regardless of whether upwelling increased or decreased, it is possible that the strengthening of the monsoon boosted productivity off the coasts of NorthernLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Western Africa because the increased river discharge delivered more nutrients to the sea.[136] The decline of dust input may have caused the cessation of deep-water coral growth in the eastern Atlantic during the AHP by starving them of nutrients.[137]

### Arabia

Precipitation in Dhofar and southwestern Arabia is brought by the African monsoon,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and a change to a wetter climate resembling Africa has been noted in southern ArabiaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Socotra from cave and river deposits.[138] It possibly reached as far as Qatar.[139] Holocene paleolakes are recorded at Tayma, Jubbah,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in the Wahiba Sands of OmanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and at Mundafan.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Rub al-Khali lakes formed between 9,000 and 7,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and dunes were stabilized by vegetation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although the formation of lakes there was less pronounced than in the Pleistocene.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". One of these lakes eventually overflowed to produce an outburst flood north of the Rub al-Khali.[140] The Wadi ad-Dawasir river system in central Saudi Arabia became active againLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with increased river runoff into the Persian Gulf.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Wadis in Oman eroded across LGM dunesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and formed accumulation terraces.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Episodes of increased river discharge occurred in YemenLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased precipitation is recorded in the caves of Hoti, Qunf in Oman, Mukalla in Yemen and Hoq Cave in Socotra.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased precipitation resulted in increased groundwater flow, generating groundwater-fed lakes and carbonate deposits.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Forests and wildfire activity expanded across parts of Arabia.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Freshwater sources in Arabia during the AHP became focus points of human activityLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and herding activity between mountains and lowlands occurred.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In addition, karstic activity took place on exposed coral reefs in the Red Sea and traces of it are still recognizable today.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased precipitation has been also invoked to explain decreased salinities in the Red Sea,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". increased sedimentation[141] and increased river inflow, while dust input decreased.[142] Rock art depicts wildlife that existed in Arabia during the humid period.[143] The Arabian neolithic coincides with the humid period,[144] with archaeological sites such as cairns appearing with its beginning,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and settlement of southern Mesopotamia during the Ubaid period may coincide with the wet epoch.[145]

The humid period in Arabia did not last as long as in Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". deserts did not retreat as muchLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and precipitation may not have reached the centralLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and northern part of the peninsulaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". past OmanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Yemen Highlands;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". northern Arabia remained somewhat drier than southern Arabia,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". droughts were still commonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the land and still produced dust.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". One study has estimated that the amount of rainfall in the Red Sea did increase to no more than Lua error: Internal error: The interpreter has terminated with signal "24"..Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Whether some former lakes in Arabia were actually marshes is contentious.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### East Africa

Nile discharge was higher than today[81] and during the early African humid period, the Nile in Egypt flooded up to Lua error: Internal error: The interpreter has terminated with signal "24".[81] higher than it did recently before flood control.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The increased flooding may have turned the Nile DeltaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Nile Valley marshy and inhospitableLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and could explain why many archaeological sites along the Nile were abandoned during the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with violent conflicts taking place at Jebel Sahaba archaeological site.[146] Early after the Younger Dryas, the Blue Nile would have been the major source of waters for the Nile.[147] Waters from the Nile[lower-alpha 20] filled depressions like the Fayum DepressionLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". to form a deep lake with anoxic bottom watersLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and reaching Lua error: Internal error: The interpreter has terminated with signal "24". above sea level,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". probably once a geomorphic barrier was breached.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Wetlands and anastomosing channels developed in the Nile DeltaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as sediment supply increased.[148] In addition, Nile tributaries in northwestern Sudan[149] such as Wadi Al-Malik,[81] Wadi Howar[lower-alpha 21]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Valley of the Queens became active during the AHP[150] and contributed sediments to the Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Wadi Howar was active until 4,500 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and at the time often contained dune-dammed lakes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". swampsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and wetlands;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". it was the largest Saharan tributary of the NileLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and constituted an important pathway into sub-Saharian Africa.[81] Conversely it appears that Lake Victoria and Lake Albert were not overflowing into the White Nile for all of the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the White Nile would have been sustained by overflow from Lake Turkana.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There appears to be a tendency over the course of the AHP for the discharge of the Blue Nile to decrease relative to that of the White Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Blue Nile built an alluvial fan at its confluence with the White Nile, and incision by the Nile reduced flooding risk in some areas which thus became available for human use.[81]

Some lakes formed or expanded during the African humid period

Closed lakes in East Africa rose, sometimes by hundreds of metres.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake Suguta developed in the Suguta Valley, accompanied by the formation of river deltas where rivers such as the Baragoi River entered the lake.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In turn, Lake Suguta overflowed into the Kerio River, this adding water to Lake TurkanaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where increased discharge by the Turkwel River led to the formation of a large river delta.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Omo River remained its principal inflow but the relative role of other water sources increased compared to present-day conditions.[151] A Lua error: Internal error: The interpreter has terminated with signal "24". deep lake filled the Chew Bahir basin[152] and together with Lakes Chamo and Abaya formed a river system flowing into Lake Turkana,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which itself overflowed on its northwestern side through the Lotikipi Swamp into the White Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Deposits from this lake highstand form the Galana Boi Formation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The increased water depth reduced water mixing in Lake Turkana, allowing organic material to build up.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This overflowing large lake was filled with freshwater and was populated by humans,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". typically in bays, along capes and protected shorelines;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the societies there engaged in fisheryLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but could probably also fall back on other resources in the region.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The EthiopianLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake Abhe expanded to cover an area of Lua error: Internal error: The interpreter has terminated with signal "24"., much larger than the present-day lake, in the "Abhe IV"–"Abhe V" lake cycle.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The enlarged lake covered a large area west of the present-day lake, present-day lakes Afambo, Gamari and Tendaho, reducing Borawli, Dama Ale and Kurub to islands,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and possibly overflowed to the Red Sea.[153] The maximum water level was reached during the early Holocene as river discharge increased, but was later limited by partial overflow and did not rise above Lua error: Internal error: The interpreter has terminated with signal "24". again.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Deep thermal groundwater recharge occurred in the region.[154] About 9,000 years of human occupation are documented at the lake.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Archaeological sites indicate that people obtained resources from the lake and followed its riseLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and decline.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The cultural traditions at Lake Abhe appear to be unusual by AHP/African standards.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Lake Zway and Lake Shala in Ethiopia joined with Lake Abiyata and Lake Langano to form a large waterbodyLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which began overflowing into the Awash River.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Nearly all lakes in the East African Rift were affected by the AHP:Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake AshengeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Lake Hayq also in Ethiopia,[155] Lake Bogoria, Lake Naivasha[72] and Lake Nakuru-Lake Elmenteita which merged,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". all in Kenya,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Lake Masoko in Tanzania.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lakes formed in the caldera of the Menengai volcanoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in the Chalbi region east of Lake Turkana; the lake covered an area of about Lua error: Internal error: The interpreter has terminated with signal "24"..[156] A Lua error: Internal error: The interpreter has terminated with signal "24". large and Lua error: Internal error: The interpreter has terminated with signal "24". deep Lake Magadi formed in the early Holocene,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". generating the "High Magadi Beds" sediments.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This lake was fed by now-dry waterfalls and possibly from the neighbouring lake Koora.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Danakil Depression of Ethiopia freshwater conditions became established.[72] Lakes formed in depressions on the mountains around Lake Kivu.[157] Some of these lakes became connected through overflow: Lake Nakuru-Elmenteita drained northward through the Menengai caldera,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Baringo-Bogoria[lower-alpha 22] Suguta into Lake Turkana and from there into the Nile, carving gorges along the way. Lake Naivasha drained south through Lake SiriataLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". into Lake Magadi-Natron.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Overflow of several of these lakes allowed animals including Nile crocodiles and fish to propagate to the individual lake basins,[158] but at the same time hindered the propagation of many land-based mammals.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". River systems in the southern Kenya Rift region became active.[159]

A glacier on Mount Kilimanjaro. The oldest now present ice of Kilimanjaro formed during the African humid period

Glaciers stopped retreating or briefly expanded in East Africa at the beginning of the AHP before continuing retreat.[160] On Mount Kilimanjaro they may have expanded during the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". after a phase during the Younger Dryas where the mountain was ice free,[161] but the tree line also rose at that time, accompanied by soil formation.[162] The wetter climate may have destabilized the neighbouring Mount Meru volcano, causing a giant landslide that removed its summit.[163] In the Rwenzori Mountains, increased precipitation during the AHP has been linked to the occurrence of rockfalls.[164]

Erosion in catchments of East Africa increased with the beginning of the humid period but then decreased even before its end,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as the increased weathering led to the formation of soils, these in turn to the establishment of a vegetation cover that subsequently reduced additional erosion.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased weathering resulted in the increased consumption of atmospheric CO2 during the AHP.[165]

Surprisingly, and contrary to the patterns expected from precessional changes, the East African Rift also experienced a wetter climates during the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". reaching as far south as Lake Rukwa[lower-alpha 23] and Lake Cheshi into the Southern Hemisphere.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the region of the African Rift ValleyLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and African Great Lakes, pollen evidence points to the occurrence of forests including rainforest vegetation due to the increased precipitation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while today they occur only in limited areas there.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Denser vegetation also occurred at Lake Turkana,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with wooden vegetation covering almost half of the dry landLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although grasslands remained dominant.[86] Development of forest vegetation around the African Great Lakes created an interconnected environment where species spread, increasing biodiversity with effects on the future when the environment became fragmented.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Vegetation cover also increased in the Afar regionLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Ericaceae plants spread at high elevations.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Forests and moisture-requiring vegetation expanded in the Bale Mountains.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Different types of vegetation, including dryland vegetation, existed at Lake Malawi and Lake Tanganyika however,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and vegetation did not change much.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The wetter climate led to the formation of the Halalee paleosoil in the Afar regionLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and decreased wildfire activity in the Rwenzori.[167]

In East Africa, the AHP led to improved environmental conditions in terms of food and water supply, allowing early human populations to survive, grow in size and settle new regions without requiring major changes in food gathering strategies.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".[168] Pottery techniques such as the "dotted wavy line" and "Kanysore" are associated with fishing and foraging communities.[121] In Somalia, the "Bardaale" lithic industry is linked to the AHP.[169] Earlier wet and dry periods in East Africa may have influenced the evolution of humansLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and allowed their spread across the SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and into Europe.[170] Animal species took advantage too, with midge populations increasing in Lake Victoria.[171]

### Other parts of Africa and the rainforest realm

Lake Bosumtwi in Ghana rose during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".[lower-alpha 24] Evidence there also suggests a decrease in wildfire activity took place.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Tropical forests expanded in Cameroon HighlandsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Adamawa Plateau of CameroonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and moved upward at Lake Bambili also in Cameroon,[172] causing an upward shift of afromontane vegetation.[173] The core of the rainforest was probably unaltered by the African humid period, perhaps with some changes in speciesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and an expansion of their area.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There is some evidence that an "Equatorial humid period", mechanistically linked to equatorial insolation and extending into the Amazon, may have taken place in the eastern Congo region at the same time as the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or around its beginning and end.[174] The peatlands of Central Congo started developing during the African humid period and peat continues to accumulate there to this day,[175] albeit with a slowdown in the Cuvette Centrale after the end of the African humid period.[176] In the Gulf of Guinea, increased sedimentation and changed sedimentation patterns from increased river runoff decreased the activity of submarine cold seeps offshore present-day Nigeria.[177]

On São Nicolau and Brava in the Cape Verde Islands, precipitation and erosion increased.[178] In the Canary Islands, there is evidence of a moister climate on Fuerteventura,[179] La Gomera and Tenerife,[180] the laurel forests changed perhaps as a consequence of the AHP.[62] Recharge of groundwater levels have been inferred from Gran Canaria also in the Canary Islands, followed by a decrease after the end of the AHP.[181] Choughs may have reached the Canary Islands from North Africa when the latter was wetter.[182]

### Levant and Mediterranean

High latitude Africa has not undergone large scale changes in the past 11,700 years;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the Atlas Mountains may have blocked the monsoon from expanding further north.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". However, soil and tufa,[183] river valleyLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and cave deposits showing a moister climate in southern Morocco,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". increased precipitation in the Algerian highlands,[184] vegetation changes in the Middle Atlas,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". several floods in Tunisian rivers[185] and ecosystem changes which impacted steppe-dependent rodents of Northern Africa have been linked to the AHP.[186]

In the Pleistocene and Holocene humidity in the Mediterranean is often correlated to humidity in the Sahara,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the early-mid Holocene climate of Iberia, Italy, Negev and Northern Africa was wetter than today;[187] in Sicily wettening correlates with ITCZ changes in Northern Africa.[188] Mediterranean precipitation is brought by Mediterranean cyclones and the westerlies;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". either increased precipitation from the westerlies,[189] northward moisture transport from Africa[190] or monsoonal precipitation extending into the Mediterranean may have rendered it wetter.[191] While it is established,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the nature of the connection between the African Monsoon and Mediterranean precipitation is unclearLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and it was winter rainfall that increased predominantly,[192] although separating monsoonal and non-monsoonal precipitation can be difficult.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The Mediterranean Sea became less saline during the AHP, in part due to increased precipitation from the westerlies[189] but also from increased river discharge in Africa, leading to the formation of sapropel layers when the increased runoff led to the Mediterranean becoming more stratified[lower-alpha 25]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and eutrophied,[194] with changes in the main water masses of the sea.[195] The S1 sapropel layer is specifically associated with the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and with increased discharge of the Nile and other African rivers.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". These processes together with decreased dust transport by wind led to changes in the sediment patterns of the Mediterranean,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased marine nutrient availability[194] and food web productivity in the Mediterranean,[196] which impacted the development of deep-sea corals.[197]

In the Levant, wetter conditions during the AHP are recorded from Jeita Cave in Lebanon, Soreq Cave in IsraelLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and desert varnish in the Negev,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while the Dead Sea has variously been reported to have grown[192] or shrunk during the AHP. Such a decline, if it took place, and a decline of other southern European lakes were low during this period. This is unlike some earlier wet periods in the Sahara,[198] and whether the monsoon reached the southern Levant region during the AHP or there was increased winter precipitation is contentious.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The northern Mediterranean may have been drier, with more wildfire activity, during the AHP,[199] but increased summer precipitation in the European Alps has been associated with the AHP.[200]

### Southern Africa

The effects, if any, of the African humid period on Southern Africa have been unclear. Originally it was proposed that the orbitally driven changes would imply a dry period in Southern Africa which would have given way to moister conditions as the northern AHP ended,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as the ITCZ should shift its average position between the two hemispheres.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". However, the lack of paleoclimatology data with sufficient time resolution from Southern Africa has made it difficult to assess the climate there during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". More recently obtained paleoclimate data have suggested however that southern Africa was actually wetter during the AHP rather than drier,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". reaching as far as Rodrigues Island in the Indian Ocean[201] and as far as the catchment of the Orange River.[202] The area between Lake Tanganyika and Lake Malawi has been interpreted as the limit of the AHP's influence.[203]

Conversely, and consistent with the opposite reaction pattern of the Southern Hemisphere, the Zambezi River reached its lowest discharge during the AHP,[204] and precipitation in the Central African Plateau and Zambia decreases in computer simulations of a Green Sahara.[205] Thus, the AHP may not have reach southernLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or southeastern Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There may have been opposite changes in precipitation between southeast Africa and tropical East Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". separated by a "hinge zone".Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Particular changes occurred in central southern Africa, where a dry period co-occurred with an expansion of Lake Makgadikgadi; presumably the lake during this dry interval was nourished by increased wetness over the Okavango River catchment in the Angolan Highlands due to the AHP;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". peatlands formed in Angola during the AHP.[206] In general there is little consistency between Northern and Southern Africa in terms of hydrological changes during the Holocene,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and nowhere are both the start and end of the AHP apparent.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Orbitally-mediated changes in Northern Hemisphere climate affected the Southern Hemisphere through oceanic pathways involving sea surface temperatures.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Additionally, wetter periods unrelated to the AHP may have occurred after deglaciation in Southern Africa.[207]

### Numerical estimates

Estimates of the exact amount of increased precipitation vary widely.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". During the African humid period, Saharan rainfall increased to Lua error: Internal error: The interpreter has terminated with signal "24".,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and values exceeding Lua error: Internal error: The interpreter has terminated with signal "24". may have spread to 19–21° northern latitude.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the eastern Sahara, a gradient from Lua error: Internal error: The interpreter has terminated with signal "24". increment in the north to Lua error: Internal error: The interpreter has terminated with signal "24". in the south has been identified.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". An area with less than Lua error: Internal error: The interpreter has terminated with signal "24". may have remained in the Eastern Sahara however,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although its driest parts may have received 20-fold more precipitation than today.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Precipitation in the Sahara probably reached no more than Lua error: Internal error: The interpreter has terminated with signal "24".,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with large uncertainty.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Other reconstructed values of the precipitation increase indicate an annual increase of about Lua error: Internal error: The interpreter has terminated with signal "24". in Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with strong regional variation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". From lake levels and other proxies, precipitation increases of 20–33%,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". 25–40%Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24"./23-45%Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". or 50–100%[72]/40–150% have been inferred for East Africa,[165] with an increase of 40% reconstructed for Northern Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the early Holocene, there appears to have been an eastward- and northward-decreasing trend of humidity.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Additionally, at Tayma in Arabia a threefold increase appears to have occurredLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and precipitation in the Wahiba Sands of Oman may have reached Lua error: Internal error: The interpreter has terminated with signal "24"..Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Effect on other climate modes

The El Niño–Southern Oscillation is a major climate variability mode. Paleoclimatology records from Ecuador and the Pacific Ocean indicate that during the early and middle Holocene ENSO variability was suppressed by about 30–60%, which can be only partially explained through orbital forcing.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Green Sahara may have suppressed ENSO activity, forcing a La Niña–like climate state,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in one climate model this is accompanied by decreased upwelling and deepening of the thermocline in the Eastern PacificLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as the Walker circulation expands westward.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Easterly winds in the western Pacific Ocean increase, while they decrease in the eastern.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In addition, Atlantic Niño sea surface temperature patterns develop in the Atlantic OceanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the South Atlantic High weakens while the circulation of the South Atlantic Ocean changes.[208] However, the existence of serious model bias in the depictions of the equatorial Atlantic sea surface temperatures is a problem for simulations of its past climateLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Atlantic Niño state may only occur during marginal AHP conditions, being suppressed during its maximum.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Remote effects of the AHP on climate have also been studied,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although many changes are model-dependent and may also be inaccurate due to incorrect depictions of atmospheric dust distribution.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Whether the reduced albedo of the Sahara during the AHP contributed to, or increased cloud cover counteracted, the warming of the Holocene thermal maximum is model-dependent;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". dust changes did not have a major effect.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The AHP would also influence SSTs in the Indian Ocean, although there is not much evidence about the mid-Holocene sea temperatures there.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The AMOC transports heat from the Southern into the Northern HemisphereLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and is implicated in starting the Holocene AHP an earlier AHPs after the end of an ice age.[209] Various studies have been conducted to determine which effects reduced dust supply and the greening of the Sahara would have had on its intensity,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with conflicting results on which effects would predominate.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased heat transport either through the atmosphere or the ocean would result in warming in the Arctic.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Gaetani et al. 2024 found that Green Sahara climate simulations feature warming throughout the Northern HemisphereLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and a strengthening of the westerlies and their precipitation in the AtlanticLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but a decline along the North American West Coast.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There are also changes in the North Atlantic Oscillation during winter.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The simulated temperature patterns, however, only poorly match temperature reconstructions.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

#### Remote precipitation and the AHP

The Sahara greening intensified the Indian and Asian monsoons,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". warmingLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased precipitation across most of the Tibetan PlateauLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". especially late in the monsoon season, and climate simulations including a green Sahara reproduce the reconstructed palaeoclimates there better than these without.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In a climate model, there is a shift in precipitation from snow to rain.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The strengthened and expanding monsoons of Africa and Asia alter the atmospheric circulation of the planet, inducing a northward-shiftedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and wetter East Asian MonsoonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and drying across tropical South America and central-eastern North America.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In East Asia, a strengthened anticyclone over the West Pacific delivers more moisture to northeastern China and Indochina, and less to central and south-eastern China.[210] The reduced dust emission warms the North Atlantic and increases westerly flow into the North American Monsoon, strengthening it.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The far-field precipitation changes reach as far as Europe and Australia.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Discrepancies between modelled and reconstructed northward extension[211] and precipitation in the Asian monsoon regions and the North American Monsoon area may be explained through these remote effects.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Sun et al. 2020 proposed that the greening of the Sahara during the AHP can increase precipitation over the Middle East even if neither the African nor the Indian monsoons reach it.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". During spring, the increased vegetation forces anomalous atmospheric circulations that direct moisture transport from the Mediterranean, the Red Sea and eastern tropical Africa into the Middle East, increasing precipitationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and agricultural productivity there.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This could explain increased precipitation in the Middle East during the AHP:Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A wet climate occurred in the Middle East during the early Holocene, leading to the Ubaid period of settlement in Mesopotamia, followed by dry phases around 5,500 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and a concomitant reduction in simulated wheat yield.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

#### Hurricanes and the AHP

One climate model has indicated that a greener Sahara and reduced dust output would have increased tropical cyclone activity, especially over the Atlantic but also in most other tropical cyclone basins.[lower-alpha 26] Changes in the intensity of the storms, decreases in wind shear, changes in atmospheric circulation and less dust in the atmosphere, which results in warmer oceans, are responsible for this phenomenon,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while tropical wave activity may have increased[74] or decreased.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The net effect could be a global increase in tropical cyclone activity, a westward shift within the ocean basinsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in the Atlantic Ocean a shift towards later dates.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". While there are no good paleotempestology data for the time of the African humid period that could confirm or refute this theoryLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and many of these records are specific for particular locations,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". hurricane activity[213] including past strikes in Puerto RicoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in Vieques appear to correlate with the strength of the West African MonsoonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and increased precipitation on the northern Yucatan Peninsula during the middle Holocene could be explained by increased hurricane activity during the AHP.[214] On the other hand, at Grand Bahama Bank and the Dry Tortugas of South Florida a decrease of hurricane activity took place during the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and dust emission is not always anti-correlated to hurricane activity.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Finally, the northward movement of the ITCZ during the AHP may have caused a corresponding northward movement of tropical cyclogenesis areas and storm tracks in the Atlantic Ocean,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which could also explain decreased hurricane activity in the Bahamas and Dry Tortugas.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

## Fluctuations

Lua error: Internal error: The interpreter has terminated with signal "24".

Temperatures in Greenland during the Younger Dryas

Climate variability during the AHP is poorly documented,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but some gaps with less precipitation took place during the late glacial and the Holocene.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". During the Younger Dryas 12,500–11,500 years ago, the North Atlantic and Europe became much colder again and there was a phase of drought in the area of the African humid period,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". extending over both East Africa,[lower-alpha 27]Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where lake levels dropped in eastern Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". southern Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". equatorial Africa[216] and West Africa. The dry interval extended to IndiaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the MediterraneanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where dune activity occurred in the Negev.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". At the end of the Younger Dryas, precipitation, lake levels and river runoff increased again, although south of the equator the return of humid conditions was slower than the relatively abrupt change to its north.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Another dry phase took place about 8,200 years ago, spanning East AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Northern Africa[lower-alpha 28] as documented by various lines of evidenceLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as decreased water levels in lakes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". It coincided with cooling in the Northern Atlantic,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in surrounding landmasses such as GreenlandLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and around the world;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the drought may be related to the 8.2 kiloyear eventLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which separates the Greenlandian and Northgrippian stages of the Holocene[218] and lasted for about one millennium.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The 8,200 year event has also been noted in the Maghreb, where it is associated with a transition of the Capsian culture[219] as well as with cultural changes both in the Sahara and the Mediterranean;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". at the Gobero cemetery a population change occurred after this dry interruptionLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but the occurrence of widespread cultural changes appears to be questionable.[220] This episode appears to have been caused by the draining of ice-dammed lakes in North AmericaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although a low latitude origin has also been suggested.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Cooling of the Northern Atlantic during Heinrich event 1 and the Younger Dryas associated with a weaker Atlantic meridional overturning circulation leads to atmospheric pressure anomalies that shift the African Easterly Jet and precipitation belts south, making Northern Africa drier.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Storm tracks shift north away from the Mediterranean.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Earlier Heinrich events were also accompanied by drought in North Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Likewise, a weakening of moisture transport and a less eastward position of the Congo Air Boundary contributed to reducing precipitation in East AfricaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although some parts of southern Africa at Lake Malawi were wetter during the Younger Dryas.[221]

Many humidity fluctuations in the early Holocene appear to be caused by the discharge of meltwater from the Laurentide Ice Sheet into the Atlantic, which weakens the Atlantic meridional overturning circulation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some dry periods in marine cores in the Gulf of Guinea appear to coincide with events recorded in Greenland ice cores.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Other variations in precipitation observed in records have been attributed to solar activity changes,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". water levels of Lake Turkana for example appear to reflect the 11-year solar cycle.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

In Lake Turkana, water level fluctuations took place between 8,500 and 4,500 years before present, with highstands before 8,400, around 7,000 and between 5,500 and 5,000Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and lowstands around 8,000, 10,000 and 12,000 years before present.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In total, five[222] or six separate highstands are recorded in desert varnish around the lake,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". matching with phases of increased wetness in the Negev.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The highstands appear to be controlled by sea surface temperature patterns in the Atlantic and Indian Oceans, but also by overflow of water from Lake SugutaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Chew Bahir and upstream lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". into Lake Turkana.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Volcanic and tectonic phenomena occur at Lake Turkana, but do not have the magnitude required to explain large changes in lake level.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Water level fluctuations have also been inferred for Lake Chad on the basis of pollen data, especially towards the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Taoudenni lake fluctuations of about a quarter-millennium have been recordedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and frequent droughts occurred in the Eastern Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Other variations appear to have occurred 9,500–9,000 and 7,400–6,800Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as well as 10,200, 8,200, 6,600 and 6,000 years before present; they were accompanied by decreased population density in parts of the Sahara,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and other dry interludes in Egypt have been noted 9,400–9,300, 8,800–8,600, 7,100–6,900 and 6,100–5,900 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The duration and severity of dry events is difficult to reconstructLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the impact of events like the Younger Dryas is heterogeneous even between neighbouring areas.[223] During dry episodes, humans might have headed to waterbodies which still had resources,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and cultural changes in the central Sahara have been linked to some dry episodes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Aside from fluctuations, a decrease in Nile dischargeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and southward retreat of the humid period may have been underway after 8,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with a major drought around 7,800 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

## End

Lua error: Internal error: The interpreter has terminated with signal "24".

The African humid period ended about 6,000–5,000 years ago;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". an ending date of 5,500 years before present is often used.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". After vegetation declined,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the Sahara became barren and was claimed by sand.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Wind erosion increased in northern Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and dust export from the now-desertLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and from dried up lakesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as the Bodélé Basin grew; Bodélé today is the largest single source of dust on Earth.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The lakes dried up, mesic vegetation disappeared, and sedentary human populations were replaced by more mobile cultures.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The transition from the "green Sahara" to the present-day dry Sahara is considered to be the greatest environmental transition of the Holocene in northern Africa;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". today almost no precipitation falls in the region.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The end of the AHP but also its beginning could be considered a "climate crisis" given the strong and extended impact.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Drying extended as far as the Azores,[224] Canary Islands[225] and southeastern Iran,[226] and there is evidence of climate change on São Nicolau, Cape Verde.[227]

The Piora Oscillation cold period in the AlpsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". coincides with the end of the AHP;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the period 5,600–5,000 years ago was characterized by widespread cooling and more variable precipitation changes around the world[228] and was possibly forced by changes in solar activity and orbital parameters.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". It has also been named "Mid-Holocene Transition".Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some changes in climate possibly extended into southeastern Australia,[229] Central America[230] and into South America.[231] The neoglacial began.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Chew Bahir basin, several short droughts may have "heralded" the end of the AHP; such short-term climatic fluctuations are common before a major climatic change.[114]

A major pan-tropical environmental change took place about 4,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This change was accompanied by the collapse of ancient civilizations, severe drought in Africa, Asia and the Middle East and the retreat of glaciers on Mount KilimanjaroLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Mount Kenya.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Chronology

Whether the drying happened everywhere at the same time and whether it took place in centuries or millennia is unclearLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in part due to disagreeing recordsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and has led to controversy,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and such a disagreement on timing also exists with respect to the expected vegetation changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Marine cores usually indicate an abrupt changeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but not without exceptionsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while pollen data do not, perhaps due to regional and local differences in vegetation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Africa is a diverse landscapeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and groundwater and local vegetation can modify local conditions;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". groundwater-fed water bodies for example persisted longer than those nourished by rain.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The debate on how quickly the Sahara formed goes back to 1849, when the Prussian naturalist Alexander von Humboldt suggested that only a quick drying could form the desert.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

In the 2010s the idea has taken hold that the end of the African humid period occurred from north to south in a stepwise fashion.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In northeastern Asia,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the western Sahara and east Africa the humid period ended within 500 yearsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with a one-step drying 6,000 – 5,000 years ago north of the present-day monsoon belt. Farther south, precipitation decrease was more protractedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and closer to the equator the AHP ended between 4,000Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and 2,500 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In East Africa, pronounced drying occurred between 4,500 and 3,500 years ago, centered on 4,000 years ago;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Egypt during the Old Kingdom was still wetter than today.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A later end in northeast Africa about 4,000 years ago may reflect the different configuration of landmasses and thus monsoon behaviour,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while other research has found a westward propagating drying trend.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". An earlier end by 6,100 years ago has also been suggested.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Some evidence points to a two-phase change in climate with two distinct dry transitionsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". caused by the existence of two different steps of insolation decrease at which climate changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Distinct environmental changes may have occurred in Central Africa, Western Africa and East Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Asia, an abrupt drying has been noted in numerous Chinese lakes.[232] Finally, sometimes the 4.2 kiloyear event – the transition from the Northgrippian to the Meghalayan stage of the Holocene – [218] is considered to be the true end of the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". especially in central Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Increased variability in precipitation may have preceded the end of the AHP; this is commonly observed before a sudden change in climate.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Gilf Kebir, between 6,300 and 5,200 years ago apparently a winter rainfall regime became established as the AHP ended.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Later fluctuations in climate that produced brief humid spells also took place,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as moister periods 2,100 years before present in the western Sahel,[62] between 2,200 - 1,500 years ago in Ethiopia[64] and between 500 BCE – 300 CE in Roman Northern Africa and along the Dead Sea.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". By 2,700 years ago the central Sahara had become a desert and remained one until the present-day.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Sahara and Sahel

After a first brief lake level dropLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". between 5,700 and 4,700 calibrated years ago that might reflect climate variability towards the end of the African humid period,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". water levels in Lake Megachad decreased quickly after 5,200 years before present.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". It shrank to about 5% of its former size,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with the deeper northern Bodele basin drying up entirely about 2,000Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".–1,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as it was disconnected from the southern basin where its major tributary, the Chari River, enters Lake Chad.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The dried out basin was now exposed to the Harmattan winds, which blow dust out of the dry lake bed,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". making it the single largest source of dust in the world.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Dunes formed in the dried-up SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Sahel[233] or began moving again after stabilizing during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The tropical vegetation was replaced by desert vegetation, in some places suddenly and in others more gradually.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Along the Atlantic coast, the vegetation retreat was slowed by a stage of sea level rise that increased soil moisture levels, delaying the retreat by about two millennia.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A gradual decline has been noted in the Tibesti.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Libya at Wadi Tanezzuft the end of the humid period was also delayed by leftover water in dune systems and in the Tassili mountains until 2,700 years ago, when river activity finally ceased.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A brief moist pulse between 5,000 – 4,000 years ago in the Tibesti led to the development of the so-called "Lower Terrace".Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Egyptian Sahara might still have been vegetated until 4,200 years ago, based on depictions of savanna environments in Fifth Dynasty tombs in Egypt.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

At Lake Yoa, which is groundwater-fed,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". vegetation decreased and the desert took over between 4,700–4,300 and 2,700 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while the lake became hypersaline 4,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lake Teli dried out completely about 4,200 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". However, the climate of the Ounianga lakes may have been affected by the Tibesti Mountains and the end of the AHP thus delayed,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and fossil groundwater left by the AHP nourishes the lake to this day.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the central Sahara, water resources in the mountains persisted longer.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### East Africa and Arabia

In northern East Africa, water levels dropped rapidly about 5,500 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while in Hoti cave in Arabia a southward retreat of the Indian Monsoon took place about 5,900 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Drying is also documented from Oman,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and rivers and lakes of Arabia became intermittent or entirely dry.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The Blue Nile basin became less moistLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with a noticeable decrease of Nile discharge about 4,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Decreased discharge of the Nile led to the cessation of sapropel deposition and turbidite activity off its delta,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the concentration/[234] abandonment of river channels in its delta and upstream[235] and increased seawater influence in the delta.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Reconstructions from Lake Abiyata in Ethiopia suggest that the end of the African humid period took the form of severe droughts rather than a gradual decrease of precipitation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Drying in Arabia commenced about 7,000 calibrated years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and there are large disparities in the timing between various parts of ArabiaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but a tendency towards an arid climate between 7,000 and 5,000 years ago has been observedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which continued until 2,700 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Bale Mountains and the Sanetti Plateau of Ethiopia vegetation changes signalling a drier climate took place around 4,600 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Forest cover in the area of the African Great Lakes decreased between 4,700 and 3,700 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although drying at Lake Rukwa began 6,700 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and transition to saline conditions took place 5,500 years ago.[166] At Lake Edward major changes in lake chemistry consistent with drying are noted 5,200 years ago. There a minor recovery in vegetation took place between 2,500 and 2,000 years ago, followed by a much more rapid appearance of grasses accompanied also by substantial wildfire activity. This might have been the most severe drought of the Lake Edward region in the Holocene, with many lakes such as Lake George dropping significantly or drying up altogether.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Other lakes such as Nakuru, Turkana, Lake Chew Bahir, Lake Abbe and Lake Zway also dropped between 5,400 and 4,200 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Decreased vegetation cover in the catchment of the Blue Nile has been correlated with increased sediment transport in the river beginning 3,600 – 4,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". 5,000 years ago, Lake Nabugabo separated from Lake Victoria owing to decreasing water levels.[236] The expansion of savanna in East Africa has been linked to the end of the AHP.[237]

The end of the AHP at Lake Turkana occurred about 5,000[222]–5,300 years before present, accompanied by a lake level declineLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the cessation of overflow from other lakes in its area into Lake Turkana.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Between 5,000 and 4,200, Lake Turkana became more saline and its water levels decreased below the level of outflow to the Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Towards the end of the AHP water temperatures in the lake and in other regional lakes appear to have increased, followed by a drop after its endLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". possibly resulting from the insolation seasonality pattern that was in force at the time of the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The decrease in water level was accompanied by a decrease in sedimentation ratesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and there is evidence that faulting and volcanism may have increased at Turkana due to the water level drop.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The decrease of water levels in Lake Turkana also impacted the Nile and the Predynastic societies dependent on it.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Mediterranean

The southern Aegean,[238] Libya and the Middle Atlas became gradually more dry,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and drying in Morocco took place about 6,000 radiocarbon years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Drier conditions in Iberia and the Western Mediterranean accompanied the end of the African humid period between 6,000 and 4,000 years ago, perhaps as a consequence of increasingly frequent positive North Atlantic Oscillation episodes and the shift of the ITCZ[239] More complicated changes have been found for the northern margin of the Mediterranean,[240] and winter rainfall increased in the Levant at the end of the AHP.[241] A 4.2 kiloyear event is recorded in dust records from the MediterraneanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and might have been caused by changes in the circulation of the Atlantic Ocean.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Tropical West Africa

In Lake Bosumtwi the African humid period ended about 3,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". after a brief moistening between 5,410 ± 80 years ago that ended 3,170 ± 70 years ago. This, earlier but similar changes off western Senegal and later but similar changes in the Congo Fan appear to reflect a southward shift of the precipitation zone over time.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some drying occurred simultaneously between the Sahel and the Gulf of Guinea.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some lakes in the Guineo-Congolian region dried out, while others were relatively unaffected.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

A general tendency towards a drier climate is observed in West Africa at the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". There, dense vegetation became progressively thinner between 5,000 and 3,000 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and major perturbations of the vegetation took place between 4,200 and 2,400 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A brief return of moister conditions took place 4,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". while a substantial dry phase occurred between 3,500 and 1,700 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Aridity became established between 5,200 and 3,600 years ago in the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Senegal mangroves collapsed 2,500 years ago[73] and modern-type vegetation arose about 2,000 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". aided by a decrease of sea level after the middle Holocene.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Central Africa

Farther south at the equator between 6,100 and 3,000 calibrated years before present savannah expanded at the expense of forests, with the transition possibly lasting until 2,500 calibrated years before present;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". a different time course estimate for the area between 4° southern and 7° northern latitude states that forest cover decreased between 4,500 and 1,300 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Adamawa Plateau (CameroonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".), the Ubangui Plateau (Central African RepublicLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".) and the Cameroon Volcanic Line montane forests disappeared at the end of the African humid period.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Adamawa Plateau savanna has continuously expanded since 4,000 calibrated years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Such a change took also place in Benin and Nigeria between 4,500 and 3,400 calibrated years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Climate around the Gulf of Guinea became drier at the end of the AHP, although forests remained stable on Sao Tome.[173] In the Congo Basin, there were changes in the composition and density of the forests rather than their extent,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and along the equator precipitation may have increased around 4.2 ka.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Many vegetation changes in the tropical regions were probably caused by a longer dry seasonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and perhaps a smaller latitudinal range of the ITCZ.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Southern Hemisphere Africa

In the Southern Hemisphere at Lake Malawi drying began later – 1,000 years before present – as did the African humid period which there began only about 8,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Contrarily, increased water levels in Etosha Pan (Namibia) appear to relate to a southward movement of the ITCZ at the end of the AHP[242] although stalagmite growth data in Dante Cave also in Namibia has been interpreted as indicating a wetter climate during the AHP.[243] Several records indicate that 5,500 years ago, precipitation changed in an east-west dipole-like wayLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with drying in the west and moistening in the east.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This pattern was probably driven by shifts in atmospheric moisture transport and of rain belt width.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Mechanisms

The end of the humid period appears to reflect the changes in insolation during the Holocene,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as a progressive decrease of summer insolation caused the insolation gradients between Earth's hemispheres to decrease.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". However, the drying appears to have been much more abrupt than the insolation changes;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". it is not clear whether non-linear feedbacks led to abrupt changes in climate and it is also unclear whether the process, driven by orbital changes, was abrupt.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Also, the Southern Hemisphere warmed and this resulted in a southward shift of the ITCZ;[244] orbitally-driven insolation has increased over the Holocene in the Southern Hemisphere.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

As precipitation decreased, so did vegetation, in turn increasing the albedo and further decreasing precipitation.[65] Furthermore, vegetation may have responded to increased variations in precipitation towards the end of the AHPLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although this view has been challenged.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This could have directed sudden changes in precipitation, although this view has been cast in doubt by the observation that in many places the end of the African humid period was gradual rather than sudden.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Plants at higher and lower latitudes might respond differently to climate change; for example more diverse plant communities might have slowed down the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Other proposed mechanisms:

* Decreases in polar insolation through altered cosmic ray fluxes might promote the growth of sea ice and cooling at high latitudes, which in turn result in stronger equator-to-pole temperature gradients, stronger subtropical anticyclones and more intense upwelling in for example the Benguela current.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Changes in the circulation of high latitude oceans may have played a role,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as the potential occurrence of another meltwater/ice rafting pulse around 5,700 years before present.[244] The decreased insolation during the mid-Holocene may have made the climate system more sensitive to changes, explaining why earlier comparable pulses did not terminate the humid period for good.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* There is evidence that glaciers in Tibet such as at Nanga Parbat expanded during the Holocene, especially towards the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In climate models, increased snow and ice on the Tibetan Plateau can lead to a weakening of the Indian and African monsoons, with the weakening of the former preceding that of the latter by 1,500–2,000 years.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Decreases in sea surface temperatures of the Indian Ocean may be involved in the drying of East Africa, but there is no agreement on the temperature records from that ocean.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Moreover, there is no evidence of temperature changes in the Gulf of Guinea at the critical time that might explain the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Additional feedback processes may have included the drying of soils and loss of vegetation after decreased rainfall,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which would have led to wind-driven deflation of the soils.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* An expansion of sea ice around Greenland, Ellesmere Island 6,000Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and Antarctica about 5,000 calibrated years ago may have provided another positive feedback.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* The expanding dry belt of the Sahara pushed the regions of cyclogenesis in the Mediterranean northwest-northward, resulting in wind changesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and precipitation regime changes in parts of Italy.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
* Climate change at high latitudes has been proposed as a cause for the end of the AHP. Specifically, about 6,000–5,000 years ago the Arctic became colder, with sea ice expanding, temperatures in Europe and off Northern Africa decreasing and the Atlantic meridional overturning circulation weakening.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This cooling tendency may have weakened the Tropical Easterly Jet and thus reduced the amount of precipitation falling over Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The orbitally-induced changes of precipitation may have been modified by the solar cycle; specifically, solar activity maxima during the ending phase of the AHP may have offset the orbital effect and thus stabilized precipitation levels, while solar activity minima compounded the orbital effects and thus induced rapid decreases in water levels of Lake Turkana.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". At Lake Victoria on the other hand, solar variations appear to sometimes lead to drought and sometimes lead to wetness, probably due to changes in the ITCZ.[244]

#### Potentially human-mediated changes

Major changes in vegetation in East Africa about 2,000 years ago may have been caused by human activity, including large-scale deforestation for iron production during the Iron Age.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Similar changes have been observed on the Adamawa PlateauLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". (CameroonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".) but later dating of archaeological sites has found no correlation between human expansion in Cameroon and environmental degradation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Similar rainforest degradation across Western African took place between 3,000 and 2,000 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the degradation is also known as "third millennium rainforest crisis".Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Climate-mediated processes may have increased the impact of land use changes in East Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Sudanian and Sahelian savannah on the other hand human activity seems to have had little impact,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and in Central Africa forest changes were clearly triggered by climate change with little or no evidence of anthropogenic changes.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The question has led to intense debate among paleoecologists and archaeologists.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

While humans were active in Africa during the end of the African humid period, climate models analyzed by Claussen and colleagues 1999 indicate that its end does not need any human activity as an explanationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". although vegetation changes may have been induced by human activityLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and grazing.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Later it was suggested that overgrazing may have triggered the end of the AHP around 5,500 years ago;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". human influence might explain why the Sahara became a desert without the accompanying onset of an ice age; usually the existence of a Sahara desert is associated with the expansion of high latitude glaciers.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Later research has on the contrary suggested that human pastoralism may have actually delayed the end of the AHP by half a millenniumLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as moving herds of animals driven by humans seeking good pasture conditions may lead to more balanced impacts of pastures on the vegetation and thus to greater vegetation quality.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Which effects prevailed is still controversial.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased grazing has been invoked to explain the increase in dust emissions after the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The effects of grazing on vegetation cover are context-dependent and hard to generalize over wider regions.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

### Global

A general drying tendency is observed in the northern tropicsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and between 5,000 – 4,500 calibrated years ago the monsoons weakened.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Perhaps as a consequence of the end of the AHP,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Asian monsoon precipitation declined between 5,000 and 4,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A drought 5,500 years ago is recorded in Mongolia[245] and eastern America, where drought conditions around 5,500–5,000 years ago occurred in places like Florida[246] and between New Hampshire and Ontario.[247] A drying tendency is also noted in the Caribbean and the Central Atlantic.[248] The final retreat of vegetation from the Sahara may have helped cause the 4.2 kiloyear event.[249]

Conversely, in South America there is evidence that the monsoon behaves in an opposite fashion consistent with precessional forcing;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". water levels in Lake Titicaca were low during the middle Holocene and began to rise again after the end of the AHP.[250] Likewise, a trend towards increased wetness took place in the Rocky Mountains at this time[251] although it was accompanied by a drier phase around Lake Tahoe, California and in the Western United States.[252] Widespread climate change occurred around the North Atlantic at the time the AHP ended, and there are connections between North American and African climate.[253] The end of the AHP may have reduced heat transport into the Arctic, causing cooling there.[254]

### Consequences

#### Humans

As observed in archaeological sites, settlement activity decreased in the Sahara after the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Beginning from the north,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". population in Northern Africa decreased between 6,300 - 5,200[111] or 5,300 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". taking less than a millennium.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In inner Arabia many settlements were abandoned about 5,300 years agoLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and there was a transition in Arabian monument construction.[255] Some Neolithic people in the desert persisted for longer thanks to the exploitation of groundwater.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Different human populations responded to the drying in diverse manners,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with responses in the Western Sahara being distinct from those in the Central Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Sahara, subsistenceLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and pastoralism replaced hunter-gatherer activityLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and a more nomadic lifestyle replaced semi-sedentary lifestylesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as observed in the Acacus Mountains of Libya.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Nomadic lifestyles also developed in the Eastern Sahara/Red Sea Hills in response to the end of the AHP.[256] There was a shift in domestic animal use from cattle to sheep and goats as these are more suited in arid climates, a change reflected in rock art from which cattle disappeared at this time.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The development of irrigation systems in Arabia may have been an adaptation to the drying tendency.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The decreased availability of resources forced human populations to adapt,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in general fishing and hunting declined in favour of farming and herding.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". However, the effects of the end of the AHP on human food production have been subject to controversy.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The pyramids of Giza, the most recognizable trace left by the Egyptian civilization

The warm episode and coinciding drought may have triggered animal and human migration to less inhospitable areasLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the appearance of pastoralists where previously fishery-dependent societies had existed, as happened at Lake Turkana.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Humans moved to the Nile,[lower-alpha 29] where the society of Ancient Egypt with pharaohs and pyramids was eventually forged by these climate refugeesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". perhaps reflecting renewed exuberance;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". thus the end of the AHP can be considered responsible for the birth of Ancient Egypt.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Lower water levels in the Nile also aided the settlement of its valley as has been observed at Kerma.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A similar process may have led to the development of the Garamantian civilization.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Such human migrations towards more hospitable conditions along rivers and the development of irrigation also took place along the Euphrates, Tigris and Indus, leading to the development of the Sumerian and Harappan civilizations.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". During the so-called "Dark Millennium" between 6,000–5,000 years ago, people left the southern coast of the Persian Gulf for more hospitable areas in what is present-day Oman.[258] Population shifts into mountain areas have also been reported for the Air Mountains, Hoggar and Tibesti.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In other places, such as the Acacus Mountains, populations conversely remained in oasesLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and hunter-gatherers also stayed in the Horn of Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The Nile itself was not totally unaffected however;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the 4.2 kiloyear eventLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the end of the AHP may be linked to the collapse of the Old Kingdom in EgyptLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". when the Nile floods failed for three decades around 4,160 years before presentLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the final drying occurred.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The ongoing decrease of precipitation after the end of the AHP could be the cause of the end of the Akkadian Kingdom in Mesopotamia.[259] The end of the Garamantian civilization may also relate to climate change although other historical events were probably more important;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". at Tanezzuft oasis after 1,600 years ago it certainly relates to the drying trend.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

In Central Africa, forests became discontinuous and savannahs formed in some places, facilitating the movement and growth of Bantu speaking populations;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". these in turn may have affected the ecosystem.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The vegetation changes may have aided in the establishment of agriculture.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The relatively slow decline of precipitation gave humans more time to adapt to the changing climate conditions.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In East Africa, the beginning of the "Pastoral Neolithic" and the appearance of Nderit pottery have been attributed to the climatic changes at the end of the AHP.[260]

Cultural changes may also have occurred as a consequence of climate change, such asLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". changes in gender roles, the development of elites,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the increased presence of human burials where formerly cattle burials predominated,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". as well as an increase of monumental architecture in the Sahara may have also been a response to increasingly adverse climates.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A spread in cattle domestication at the time of climate changeLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and as herders escaped the drying Sahara southwards[261] may also relate to these events, although the details of the exact process by which cattle domestication spread are still controversial.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Finally, changes in agricultural practices at the end of the AHP may be associated with the propagation of malaria and one of its causative pathogens Plasmodium falciparum; in turn these may correlate with the origin of human genome variants such as sickle cell disease that are linked to malaria resistance.[262]

#### Non-human

In the Sahara, animal and plant populations were fragmented and restricted to certain favoured areas such as moist areas of mountain ranges; this happened for example to fish and crocodiles which only persist in isolated water bodies. Mediterranean plantsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as cypresses too persist only in mountains,[263] along with some reptiles that may have also been stranded in mountains by the drying.[264] The whip spider Musicodamon atlanteus is probably also a relic of past wetter conditions.[265] The development of human-specific populations of the malaria-transmitting mosquito Aedes aegypti coincides with the end of the AHP.[266] The buffalo species Syncerus antiquus probably went extinct from the increased competition of pastoralists triggered by the climate drying.[267] Goat populations in Ethiopia shrunk during the droughts that followed the end of the AHP[268] lion[269] and possibly barley habitat declined across Africa.[270] The drying of the African Great Lakes region split gorilla populations into western and eastern populations,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and a similar population split between the insect species Chalinus albitibialis and Chalinus timnaensis in Northern Africa and the Middle East may have also been caused by the expansion of deserts there.[271] Some aquatic species disappeared from the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Giraffes, widespread in the Sahara during the AHP, may have been forced to migrate into the Sahel; this together with the separating effect of Lake Megachad may have influenced the development of giraffe subspecies.[272] Climate change together with human impacts may have led to the extinction of a number of large mammals in Egypt,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as the hartebeest in the Sahara.[273] In the Ruwenzori Mountains, vegetation changes may have been enhanced by climatic cooling.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In northern Madagascar, wildlife declined after the end of the AHP even before the arrival of humans.[274] On the other hand, the decline of tree cover may have grown the niche available to domestic animals,[275] and modern Afromontane vegetationLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and some drought-tolerant plant species may have expanded their range.[276]

The Dahomey Gap[lower-alpha 30] formed 4,500–3,200 years before present, correlative to the end of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The harbour porpoise declined in the Mediterranean due to a switch to oligotrophic conditions as discharge from African rivers decreased.[196] Desert varnish formed on exposed rocks in the SaharaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and at Lake Turkana in East Africa.[222] Tectonic faultingLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and mass wasting eroded shorelines left by the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

#### Global climate

The shrinkage of subtropical wetlands probably led to a drop in atmospheric methane concentrations between 5,500 and 5,000 years ago, before boreal wetlands expanded and offset the loss of subtropical wetlands, leading to a return of higher atmospheric methane concentrations.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Conversely, increases in atmospheric methane concentrations, detected in Greenland ice cores about 14,700 years ago,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and atmospheric carbon dioxide decreases in the early Holocene may relate to the vegetation expansion caused by the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The concentration increase beginning 7,000 years ago may reflect increased aridity,[259] although other processes were probably more important.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Dust originating in the Bodele depression

A sudden increase in the amount of land-originating dust in an oceanic drill core off Cape Blanc, Mauritania, has been interpreted as reflecting the end of the AHP 5,500 years ago occurring in only a few centuries.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Increased African dust deposition took place at Ciomad,[278] central Portugal[279] and the Durmitor Massif, all in Europe.[280] Potentially, alluvial[lower-alpha 31] sediments emplaced during the AHP[282] and dried up lake basins became an important source for dustLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and silt-sized particles.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Today, the Sahara is the single largest source of dust in the world,[lower-alpha 32] with far ranging effects on climate and ecosystems,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". such as the growth of the Amazon rainforest.[283]

In one climate model, the desertification of the Sahara at the end of the AHP reduces the amount of heat transported in the atmosphere and ocean towards the poles, inducing cooling of Lua error: Internal error: The interpreter has terminated with signal "24". especially in winter in the Arctic and an expansion of sea ice. Reconstructed temperatures in the Arctic indeed show a cooling, although less pronounced than in the climate model.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Further, this climate transition in the climate model is accompanied by increased negative Arctic Oscillation states, a weaker subpolar gyre and increased precipitation and cold air outbreaks in much of Europe; such changes have also been observed in paleoclimate data.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". These findings imply that the vegetation state of the Sahara influences the Northern Hemisphere climate.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In turn, this high latitude cooling may have further reduced precipitation over Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Hou et al. 2024 proposed that the drying of the Sahara induced drying in northern China and moistening in southern China,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". through a cooling in the Indo-Pacific Warm Pool and an eastward shift of the Walker circulation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This was accompanied by cultural changes in China, with a decline in the number of archeological sites,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the Walker circulation change may be a causal mechanism for the 4.2 ka event.[284]

## Present-day situation

Presently, the African Monsoon still influences the climate between 5° south and 25° north latitude; the latitudes around 10° north receive the bulk of their precipitation from the monsoon[lower-alpha 33] during summer, with smaller amounts of rainfall occurring farther north. Thus farther north deserts can be found while the moister areas are vegetated.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In the Central Sahara, annual precipitation reaches no more than Lua error: Internal error: The interpreter has terminated with signal "24"..Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Even farther north, the margin of the desert coincides with the area where the westerlies bring precipitation;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". they also influence southernmost Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Subsidence of air over parts of Northern Africa is responsible for the existence of deserts, which is further increased by the radiative cooling over the desert.[1] Climate variability exists to this day, with the Sahel suffering from droughts in the 1970s and 1980s when precipitation decreased by 30% and the flow of the Niger River and Senegal River even more,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". followed by an increase of precipitation.[1] The droughts are one of the most significant climate anomalies of the 20th century.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Sea surface temperatures and feedbacks from land surface conditions modulate the strength of the monsoonLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the droughts may have been triggered by sea surface temperature changes forced by anthropogenic aerosols.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A large increase in dust fluxes after 1800 AD has been explained with changed agricultural practices.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

In East Africa the monsoon leads to two rain seasons in the equatorial area, the so-called "long rains" in March–May and the "short rains" in October–NovemberLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". when the ITCZ moves northward and southward over the region, respectively;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". in addition to the Indian Ocean-sourced precipitation there is also Atlantic[lower-alpha 34]\- and Congo-sourced precipitation west of the Congo Air Boundary.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Arabia, the monsoon does not penetrate far from the Arabian Sea and some areas are under the influence of winter precipitation brought by cyclones from the Mediterranean Sea.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". East Africa is also under the influence of monsoon circulations.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". South Africa has both monsoonal climates, winter precipitation climates and climates without clear precipitation seasonality.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

## Implications for future global warming

Greening of the Sahel between 1982 and 1999

Some simulations of global warming and increased carbon dioxide concentrations have shown a substantial increase in precipitation in the Sahel/Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". This and the increased plant growth directly induced by carbon dioxideLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". could lead to an expansion of vegetation into present-day desert, although it would be less extensive than during the mid-HoloceneLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and perhaps accompanied by a northward shift of the desert, i.e. a drying of northernmost Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Such a precipitation increase may also reduce the amount of dust originating in Northern Africa,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with effects on hurricane activity in the Atlantic and increased threats of hurricane strikes in the Caribbean, the Gulf of Mexico and the East Coast of the United States.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

The Special Report on Global Warming of 1.5 °C and the IPCC Fifth Assessment Report indicate that global warming will likely result in increased precipitation across most of East Africa, parts of Central Africa and the principal wet season of West Africa, although there is significant uncertainty related to these projections especially for West Africa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In addition, the end of the 20th century drying trend may be due to global warming.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". On the other hand, West Africa[285] and parts of East Africa may become drier during given seasons and months.[285] Currently, the Sahel is becoming greener but precipitation has not fully recovered to levels reached in the mid-20th century.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Climate models have yielded equivocal results about the effects of anthropogenic global warming on the Sahara/Sahel precipitation. Human-caused climate change occurs through different mechanisms than the natural climate change that led to the AHP:Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Human-mediated climate change drives increased precipitation mainly through increased atmospheric moisture availabilityLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and disproportionate warming of the extratropics which strengthen the monsoon circulation,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". moderated by increased atmospheric stability, while the natural climate change is driven by a stronger monsoon circulation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The direct effect of heat on plants may be detrimental.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Non-linear increases in vegetation cover are also possible,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". with several climate models showing abrupt increases when global temperatures rise by Lua error: Internal error: The interpreter has terminated with signal "24"..[286] One study in 2003 showed that vegetation intrusions in the Sahara can occur within decades after strong rises in atmospheric carbon dioxideLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but would not cover more than about 45% of the Sahara.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". That climate study also indicated that vegetation expansion can only occur if grazing or other perturbations to vegetation growth do not hamper it.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". On the other hand, increased irrigation and other measures to increase vegetation growth such as the Great Green Wall could enhance it.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". A 2022 study indicated that while increased greenhouse gas concentrations by themselves are not sufficient to start an AHP if greenhouse gas-vegetation feedbacks are ignored, they lower the threshold for orbital changes to induce Sahara greening.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Creation of rivers and lakes from the 2024 monsoon in the Sahara

Plans to geoengineer the Sahara to increase its vegetation cover and precipitation have been proposed since the 19th century.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". The mechanisms and consequences of the AHP are important context to evaluate such proposals and their ramifications;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". precipitation may increaseLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but the consumption of carbon dioxide would be small and there could be detrimental impacts on climate and dust fluxes in the far-field.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Building the Great Green Wall[287] and large solar farms in the Sahara desert would also act to decrease its albedo and may trigger similar climate responses.[288]

A greening of the Sahara on the one hand may allow agriculture and pastoralism to expand into hitherto unsuitable areas, but increased precipitation can also lead to increased water borne diseases and flooding.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Expanded human activity resulting from a wetter climate may be vulnerable to climate reversals as demonstrated by the droughts that followed the mid-20th century wet period.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

## See also

* Sahara pump theory

## Notes

1. ↑ The end of the AHP coincides with the maximum temperatures.[20] In Senegal, temperatures during the AHP were 1 °C (1.8 °F) lower than today there.[56]
2. ↑ Active dunes also formed in Arabia, IsraelLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and the exposed seafloor of the Persian GulfLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". where dust generation increased.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
3. ↑ Although the second half of Heinrich event 1 might have been wetter.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
4. ↑ Dune-covered areas.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
5. ↑ However, some lakes persisted in areas where colder temperatures had decreased evaporation.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
6. ↑ Earlier it was thought that it had started about 9,000 years ago, before it was found that it probably began earlier and was interrupted by the Younger Dryas;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". the older hypothesis has not been entirely abandonedLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and sometimes the AHP is subdivided into a "terminal Pleistocene" and "early Holocene" AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Some lake level curves indicate a stepwise increase of lake levels 15,000 ± 500 and 11,500–10,800 years ago, before and after the Younger Dryas.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
7. ↑ Whether it commenced first in the eastern Sahara is unclear.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
8. ↑ Tephrochronological data support a gradual advance.[63]
9. ↑ This was originally believed to have occurred 7,000 or 13,000 years before present,Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but a more recent suggestion indicates a reconnection of the Nile 14,000–15,000 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
10. ↑ Lake Megachad is an expanded Lake ChadLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which had a size comparable to the Caspian SeaLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". which is today's largest lake.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
11. ↑ The Congo Air Boundary is the point at which moisture bearing winds from the Indian Ocean collide with those from the Atlantic OceanLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and separates the region influenced by August-September rains from the region that remains dry during that season.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
12. ↑ The Red Sea Trough is a low pressure system in the atmosphere, that extends from the southern Red Sea and the ITCZ there to the Levant and Mediterranean, and plays a role in autumn precipitation in the region.[75]
13. ↑ In the Caribbean, a wet period has been identified in the mid-Holocene which correlated with the African wet period and was preceded and followed by drier conditions.[76]
14. ↑ Where the Monsoon of South Asia penetrated farther inlandLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". and was more intense starting about 14,800 years ago.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In Central Asia, increased snowmelt and changes in the Westerlies caused roughly synchronous but unrelated precipitation increases.[77]
15. ↑ Both Bir Kiseiba and Nabta Playa feature archaeological sites;Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Nabta may have been a religious centre of regional importance.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
16. ↑ Overflowing lakes and alluvial fans established further connections between watersheds.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
17. ↑ Which may have expanded into previously dry areas at the beginning of the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
18. ↑ Fesselsteine are stony artifacts, that are interpreted as tools for restraining animals.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
19. ↑ In the form of calcretes, "lake chalks", rhizoliths, travertines and tufa.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
20. ↑ Local runoff contributed to the filling of the Fayum Depression.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
21. ↑ Also known as the Yellow Nile.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
22. ↑ Assuming that they merged, which is not clearly established.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Tectonic or geographic changes may have been necessary to establish a connection.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". Alternatively, water might have bypassed Baringo.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
23. ↑ Which overflowed through the Ifume River into Lake Tanganyika.[166]
24. ↑ A lake level drop 8,000 years ago has been related to the northward movement of the rainbelt.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
25. ↑ Which would prevent oxygen-rich waters from sinking to the deep ocean in winter, suffocating organisms on the seafloor.[193]
26. ↑ Except for most of the Western North Pacific according to Pausata et al. 2017.[212]
27. ↑ There is conflicting evidence on whether the Younger Dryas was wetter or drier in tropical southeastern Africa.[215]
28. ↑ Whether it also took place in Asia is unclear; perhaps it was too short to trigger climate changes recognizable in recordsLua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". but some evidence has been found.[217]
29. ↑ At the time of the Gerzeh culture,[257] later followed by the Early Predynastic.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24". In upper Egypt, the Badarian culture developed when the AHP ended.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
30. ↑ The Dahomey Gap is a region without forests in southern Benin, Ghana and Togo[277] that forms a gap in the Guineo-Congolian forest belt.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
31. ↑ Alluvium refers to sediments deposited by running water, which have not solidified into rocks.[281]
32. ↑ Roughly five times larger than during the AHP.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
33. ↑ The main area of monsoon rains does not coincide with the ITCZ.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
34. ↑ The Atlantic Ocean is also the source of monsoon rainfall for the Sahel.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".

Lua error: Internal error: The interpreter has terminated with signal "24".

## References

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## Further reading

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