US
The US emits more, absolutely and per head, than any other country. When Kyoto was agreed, the US signed and committed to reducing its emissions by 6%. But since then it has pulled out of the agreement and its CO2 emissions have increased to more than 15% above 1990 levels. As the US accounted for over 36% of world emissions, the 55% target was much harder to achieve without its participation. But 141 countries banded together and the protocol came into force in February 2005.

European Union
All 15 European Union states ratified the Kyoto deal in May 2002.
The EU has opposed widespread use of forests and other carbon 'sinks' to absorb pollution - but gave substantial ground on the issue at talks in Bonn in 2001. The EU pledged to bring total greenhouse gas emissions to 8% below 1990s levels by 2008-2012, but by 2002 they had dropped only 3%. Only four EU countries are on track to achieve their own targets.

China
China is the world's second biggest emitter of greenhouse gases. China's leaders recognise that climate change could devastate their society and ratified the Kyoto Protocol in 2002, but as a developing country China is not yet required to reduce its emissions. The average Chinese person consumes only 10-15% of the energy an average US citizen uses, but with the economy developing at high speed many analysts expect China's total emissions to overtake America's soon.

Russia
Russia ratified the Kyoto Protocol in November 2004 - the crucial moment making the treaty legally binding. Russia's economy has shrunk so drastically since 1990 that industrial activity has dropped, leaving emissions reduced by about 35% and well below the level allowed under Kyoto. In the short-term, Russia stands to gain billions of dollars through emissions trading - selling its unused emissions entitlement to developed countries which want to emit more than the protocol allows them to.