The Bush administration has decreed that carbon dioxide from industrial emissions - the main cause of global warming - is not a pollutant.
The decision by the Environmental Protection Agency - announced with minimal fanfare on the eve of the Labor Day weekend - reverses the stance taken under President Clinton and allows industry to increase emissions with impunity.
It is also part of a pattern of casting doubt on scientific evidence, going back to the US's rejection of the Kyoto Protocols in 2001. Earlier this year, the Bush administration excised a 28-page section on climate change from an EPA report. It also ignored a report by the US Academy of Sciences that argued that the evidence of climate change could not be ignored.
"Saying that carbon dioxide does not cause global warming is like refusing to say smoking causes lung cancer," said Melissa Carey, a climate change expert with the advocacy group Environmental Defense.
Environmental groups are now considering suing the EPA to force the regulation of greenhouse gases.
The Bush administration appears to be guided by a leaked memo by the political consultant Frank Luntz, which advised: "Should the public believe that the scientific issues are settled, their views about global warming will change accordingly. Therefore, you need to make the lack of scientific certainty a primary issue in the debate."Reuse content