Kyoto Protocol comes into force

BBC NEWS | Science/Nature | Kyoto Protocol comes into force

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.