In a dramatic reversal of its previous position, the White House this week conceded that emissions of carbon dioxide and other heat-trapping gases were the only likely explanation for global warming.
Citing the "best possible scientific information," an administration official, James Mahoney, delivered a report to Congress that essentially reversed the previous White House position set out by US President George Bush, who had refused to link carbon dioxide emissions to climate change.
Two years ago, when his administration last published a document claiming that global warming over the last few decades had been prompted by human behavior, Bush dismissed it as something "put out by the bureaucracy."
One of Bush's first acts on the international scene as president was to refuse to ratify the Kyoto treaty, which aimed to cut emissions by 5.2 percent from 1990 levels by 2012 -- prompting outrage throughout the world.
"We must argue with the Americans and get them to agree we have to have a global solution, and America is a very important part of that solution," British deputy prime minister, John Prescott, said at the time.
But Bush also alienated himself from members of his own Cabinet as he overrode the recommendations of his newly-appointed head of the Environmental Protection Agency, Christine Todd Whitman. This was widely seen as a payback to the energy lobby which had donated a huge amount to his campaign.
At the time Bush cast doubts on the science, claimed restrictions would hamper economic growth, and said the treaty was "unfair to the United States and to other industrialized nations" because it exempted developing countries.
However, it will be far more difficult for him to distance himself from the current report, because it has been signed by the secretaries of energy and commerce in his administration.
Coming just days before the Republican convention opens in New York, it is thought to be another attempt by the administration to show moderate leanings.
The report, which also quotes studies that indicate that carbon dioxide stimulates the growth of invasive weeds more than it does crops, is part of a regular series submitted to Congress to monitor global trends.
Bush's former allies in the energy industry criticized the findings. Myron Ebell, of the Competitive Enterprise Institute, told the New York Times it was "another indication that the administration continues to be incoherent in its global warming policies."
Environmentalists say the report's conclusions simply highlight the distance between what the Bush administration has done and what good science suggests should be done.
"For four years the Bush administration has brought the international global warming negotiations to a virtual standstill by claiming that uncertainties in climate science do not justify the cost of tackling it," said Rob Gueterbock of Greenpeace.
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