Paleoclimatology is the study of climate in the past and generally covers the time period before scientific measurements were begun. This field has expanded enormously over the past number of years as new techniques have been developed and existing ones expanded.
It is an increasingly important area because of the looming impact of global warming and the imperative to try and understand what the climate was like in the past and how it reacted, so as to help better predict the future climate and our impact on it.
Paleoclimatology encompasses a diverse range of fields most of which are still active areas of research. Measurements have been derived from tree rings, lake sediments, ocean bed sediments, ice cores from Greenland and Antarctica