US carbon emissions fell 1.5 per cent last year in spite of solid economic growth, signalling the sharpest improvement in energy efficiency for two decades.
President George W. Bush hailed the reduction as evidence that his technology-focused approach to tackling climate change could work.
Greenhouse gas intensity - carbon emissions per unit of economic activity - decreased 4.2 per cent, the biggest reduction since 1985.
Mr Bush said the figures, released by the Energy Information Administration (EIA), put the US ahead of its goal, set in 2002, to reduce greenhouse gas intensity by 18 per cent by 2012.
The findings will support Mr Bush's efforts to shed his reputation for inaction on climate change, ahead of a UN meeting on the issue in Bali, Indonesia, next month.
This year, Mr Bush issued the first US commitment to seek a long-term cut in carbon emissions and vowed to support UN efforts to negotiate a successor to the Kyoto treaty on climate change. But the US remains opposed to mandatory emissions caps, preferring voluntary cuts and incentives for technological innovation.
Environmental groups welcomed the EIA findings but voiced doubt about whether the trend could be sustained without tougher action. "Despite a small dip in 2006, EIA's analysis shows that emissions are up more than 15 per cent since 1990," said Environmental Defense. "Only a mandatory cap on emissions is going to turn that around far enough and fast enough."
White House officials attributed the fall in emissions to tougher environmental regulations and investment in cleaner and more efficient technology.
Jim Connaughton, White House environmental adviser, acknowledged this year that the weather had also helped suppress emissions in 2006 by limiting energy consumption.
The cut in emissions, while the economy grew by 2.9 per cent in 2006, reinforced Mr Bush's belief that climate change action need not interfere with growth.
"Energy security and climate change are two of the important challenges of our time," said Mr Bush. "Our guiding principle is clear: we must lead the world to produce fewer greenhouse gas emissions, and we must do it in a way that does not undermine economic growth or prevent nations from delivering greater prosperity for their people."
http://www.msnbc.msn.com/id/22014934/