The principle of common but differentiated responsibilities, enshrined in the United Nations Framework Convention on Climate Change adopted in 1992 resulted from a common understanding that the industrialised nations were then the principal actors responsible for climate change occuring as a result of industrial emissions. In line with this principle, a group of developed countries and economies in transition (EITs) agreed to take up binding emission reduction tragets under a protocol which was adopted in Kyoto, Japan, on 11 December 1997. The Kyoto Protocol entered into force on 16 February 2005. Its first commitment period (CP.1) of 5 years started in 2008, coming to an end in 2012. The countries listed in Annex B to the Protocol commited to reduce, in that period, their emissions collectively by 5% against their baseline levels, predominantly set for 1990. In the CP.1 of the Kyoto Protocol emissions reductions were undertaken by 37 countries and the European Community. Article 4 of the Kyoto Protocol enables countries to undertake joint commitments as regional blocks.
Each party with commitments in CP.1 was issued into registry a number of AAUs corresponding to its Assigned Amount. Registries were established to record and track the movement of units. Parties also agreed on the adoption of three market based mechanisms; international emissions trading (IET), joint implementation (JI) and clean development mechanism (CDM) in order to support the parties with reduction commitments in their efforts to meet their targets.
In Durban, at COP.17/CMP.7, Parties to the Kyoto Protocol agreed on the starting date of the second commitment period as 1 January 2013. New commitments for Annex I parties listed in Annex B to the Kyoto Protocol were agreed at COP.18/CMP.8 in Doha. Parties also agreed on the continuation of the flexible mechanisms, and on the rules for banking surplus AAUs from CP.1 to CP.2. The amendment contains also a revised list of greehouse gases reported by the parties with commitments in CP.2. The reduction that parties listed in Annex B aim to achieve in CP.2. would amount to at least 18 % below 1990 levels in the period until 2020. However, parties also agreed to revise their commitments in 2014, with a view of increasing ambition before 2020 (Annex I countries with pledges under the Convention were also encuraged to do so). The number of parties with commitments in CP.2 decreased. Japan, Russia, Canada and New Zealand did not take new commitments post-2012. However, two new countries: Belarus and Kazakhstan joined the Kyoto Protocol in CP.2.