The Kyoto accord, which aims to curb the air pollution blamed for global warming, has come into force seven years after it was agreed.
The accord requires countries to cut emissions of carbon dioxide and other greenhouse gases.
Some 141 countries, accounting for 55% of greenhouse gas emissions, have ratified the treaty, which pledges to cut these emissions by 5.2% by 2012.
But the world’s top polluter – the US – has not signed up to the treaty.
The US says the changes would be too costly to introduce and that the agreement is flawed.
Large developing countries including India, China and Brazil are not required to meet specific targets for now.
The ancient Japanese capital of Kyoto, where the pact was negotiated, is hosting the main ceremony marking the treaty’s coming into force.
Russia ratified the treaty in November 2004 – the crucial moment that made the treaty legally binding.
Courtesy BBC News
In context
Most climate scientists say that the targets set in the Kyoto Protocol are merely scratching the surface of the problem.
The agreement aims to reduce emissions from industrialised nations only by around 5%, whereas the consensus among many climate scientists is that in order to avoid the worst consequences of global warming, emissions cuts in the order of 60% across the board are needed.
This has led to criticisms that the agreement is toothless, as well as being virtually obsolete without US support.
But others say its failure would be a disaster as, despite its flaws, it sets out a framework for future negotiations which could take another decade to rebuild.
