Kyoto Protocol

Negotiated at the third Conference of the Parties to the UNFCCC in Kyoto, Japan, the Protocol was adopted on 11 December 1997 and entered into force on 16 February 2005. It turned the Convention's broad climate framework into a set of quantified commitments for parties listed in Annex B, chiefly industrialized countries and economies in transition. The treaty reflected the principle of common but differentiated responsibilities: its binding emission targets applied to developed parties, while it did not impose new quantified reduction commitments on developing-country parties. The target assigned to each party varied rather than being identical for all.

For the first commitment period, 2008–2012, the targets for participating industrialized countries and economies in transition added up to an average reduction of about 5 per cent below 1990 emission levels. The exact assigned amount differed by party. In 2012, parties adopted the Doha Amendment, establishing a second commitment period from 2013 through 2020. Participating parties in that period committed to reduce emissions by at least 18 per cent below 1990 levels, but the group of parties taking on targets differed from that of the first period. The amendment entered into force on 31 December 2020, after the second period had ended.

Parties were expected to meet targets mainly through domestic action, but the Protocol also established three market-based mechanisms: international emissions trading, Joint Implementation and the Clean Development Mechanism (CDM). Joint Implementation enabled qualifying projects between parties with targets to generate emission-reduction units. Under the CDM, projects in developing countries could generate certified reductions that parties with targets could use toward part of their commitments; the treaty required reductions to be real, measurable and additional to what would otherwise occur. The Protocol also set out systems for emissions inventories, reporting, expert review and compliance, intended to make performance and transactions trackable.

The IPCC's Sixth Assessment Report finds that the Protocol led to measurable and substantial avoided emissions, and that it helped build greenhouse-gas accounting capacity, foster emissions markets and increase investment in low-carbon technologies. At the same time, its binding targets covered only a defined group of developed-country parties, limiting the reach of that target system. The Paris Agreement, adopted in 2015, uses a different architecture: all parties are to communicate nationally determined contributions, rather than having Kyoto-style targets inscribed in the treaty for a subset of countries. The agreements are related parts of the UN climate regime, but the Paris framework did not simply repeat Kyoto's design.