An Assigned Amount Unit (AAU) is a tradable 'Kyoto unit' or 'carbon credit' representing an allowance to emit greenhouse gases comprising one metric tonne of carbon dioxide equivalents calculated using their Global Warming Potential.[1] [2] Assigned Amount Units are issued up to the level of initial "assigned amount" of an Annex 1 Party to the Kyoto Protocol.[3][4]
The "assigned amounts" are the Kyoto Protocol Annex B emission targets (or "quantified emission limitation and reduction objectives") expressed as levels of allowed emissions over the 2008–2012 commitment period.[5]
Article 17 of the Kyoto Protocol allows emissions trading between Annex B Parties (countries). Parties that have "assigned amount units" to spare because of reductions in emissions below their Kyoto commitment set out in Article 3 and Annex B may sell those units to countries that have emissions exceeding their targets.[6] Article 17 also requires that any such emissions trading shall be supplemental to domestic action for the purpose of meeting quantified emission limitation and reduction commitments (QELRCs).