The Kyoto Treaty commits industrialised nations to reducing emissions of greenhouse gases, principally Carbon Dioxide, by around 5.2% below their 1990 levels over the next decade.
Drawn up in Kyoto, Japan, in 1997, the agreement needs to be ratified by countries who were responsible for at least 55% of the world's carbon emissions in 1990 to come into force.
The agreement was dealt a severe blow in March 2001 when President George W Bush announced that the United States would never sign it.
A scaled-down version was drawn up four months later and finalised at climate talks in Bonn in Germany in 2002. The treaty now only needs Russian ratification to come into force.
Finance - funding for poor countries to develop new technology
Mechanisms - tough systems in each country to verify and report carbon emissions
Sinks - heavily forested countries can use their 'tree sinks' to offset greenhouse gases
Compliance - countries that fail to keep to their greenhouse gas reduction targets should face legally binding consequences
If and when the revised treaty takes effect in 2008, it will require all signatories, including 39 industrialised countries, to achieve different emission reduction targets.
With that aim, it will provide a complex system which will allow some countries to buy emission credits from others.
For instance, a country in western Europe might decide to buy rights or credits to emit carbon from one in eastern Europe which could not afford the fuel that would emit the carbon in the first place.
The US produced 36% of emissions in 1990, making it the world's biggest polluter.
The revised Kyoto agreement, widely credited to the European Union,
made considerable compromises allowing countries like Russia to offset their targets with carbon sinks - areas of forest and farmland which absorb carbon through photosynthesis.
The Bonn agreement also reduced cuts to be made to emissions of six gases believed to be exacerbating global warming - from the original treaty's 5.2% to 2%.
It was hoped that these slightly watered down provisions would allow the US to take up the Kyoto principles - but this has not proved to be the case.