Signatories to the UNFCCC are split into three groups:

• Annex I countries (industrialized countries)
• Annex II countries (developed countries which pay for costs of developing countries)

Developing countries.

Annex I countries agree to reduce their emissions (particularly carbon dioxide) to target levels below their 1990 emissions levels. If they cannot do so, they must buy emission credits or invest in conservation. Annex II countries, that have to provide financial resources for the developing countries, are a sub-group of the annex I countries consisting of the OECD members, without those that were with transition economy in 1992.

Developing countries have no immediate restrictions under the UNFCCC. This serves three purposes:

• Avoids restrictions on growth because pollution is strongly linked to industrial growth, and developing economies can potentially grow very fast.
• It means that they cannot sell emissions credits to industrialized nations to permit those nations to over-pollute.
• They get money and technologies from the developed countries in Annex II.

Developing countries may volunteer to become Annex I countries when they are sufficiently developed.

Developing countries are not expected to implement their commitments under the Convention unless developed countries supply enough funding and technology, and this has lower priority than economic and social development and dealing with poverty.

Some opponents of the Convention argue that the split between Annex I and developing countries is unfair, and that both developing countries and developed countries need to reduce their emissions. Some countries claim that their costs of following the Convention requirements will stress their economy.

These were some of the reasons given by George W. Bush, President of the United States, for, as his predecessor did, not forwarding the signed Kyoto Protocol to the United States Senate.