June 11 (Bloomberg) -- The U.S. released more carbon dioxide into the air from burning fossil fuels than any other country last year, barely keeping its lead over China, whose emissions surged on coal use, estimates based on BP Plc data show.

The biggest economy emitted 6.56 billion metric tons of the greenhouse gas in 2007, according to Bloomberg calculations using the consumption of coal, oil and natural gas published today in the statistical review of energy by BP, Europe's second-largest oil company. China's total was an estimated 6.46 billion tons.

The United Nations' Intergovernmental Panel on Climate Change said last year that if emissions blamed for global warming are left unchecked, the world's average temperature may rise by as much as 6 degrees Celsius (10.8 degrees Fahrenheit) by the end of the century, potentially causing icecaps to melt, sea levels to rise and droughts to worsen.

About 180 nations are seeking to negotiate a successor to the 1997 Kyoto Protocol, a treaty to limit climate change through 2012. They set a deadline at the end of next year.

China's emissions, largely driven by burning coal, will probably more than double to 11.4 billion tons by 2030, unless lawmakers change energy policies, the International Energy Agency in Paris said in November.

Even so, China's per-capita emissions will be less than half those in the U.S. by 2030, or 7.9 tons versus 19 tons, the IEA forecast.

The U.S. and European Union countries caused most of the existing build-up, accounting for more than half of cumulative greenhouse-gas output from 1900 to 2005. China and India contributed 8 percent and 2 percent, respectively, the IEA said.

To contact the reporter on this story: Mathew Carr in London at m.carr@bloomberg.net

Last Updated: June 11, 2008 05:46 EDT