by the Congressional Budget Office, The Economics of Climate Change… (2003)
“ To enter into force, the Kyoto Protocol must be accepted, approved, acceded to, or ratified by at least 55 signatories to the convention, including countries that together in 1990 accounted for at least 55 percent of total carbon dioxide emissions from Annex I countries. In effect, the provision means that the protocol must be ratified or approved by either the United States or Russia, which together accounted for over 50 percent of emissions from Annex I countries in that year. ”
