Evaporating hopes? Bush's decision could delay action to slow the melting of glaciers. Credit: STILL PICTURES

In a move that has dashed environmentalists' hopes that the new administration might accommodate their views on global warming, President George W. Bush has reversed a campaign pledge to place mandatory caps on the emission of carbon dioxide from power plants.

In a letter to four senators, Bush attributed his decision to the “incomplete state of scientific knowledge of the causes of, and solutions to, global climate change and the lack of commercially available technologies for removing and storing carbon dioxide”.

Bush's action was widely criticized by environmentalists, European government officials and moderate Republicans. Sherwood Boehlert (Republican, New York), chair of the Science Committee in the House of Representatives, called it “a misguided and unjustified reversal of position”.

On 14 March, the day after Bush's announcement, Boehlert's committee held a meeting on climate-change research at which all witnesses testified that greenhouse-gas emissions were contributing to global climate change. Boehlert later said: “I've got some advice for the president: pay attention to the scientific enterprise.”

Legislation to amend the Clean Air Act so as to cap carbon dioxide emissions has been proposed by Boehlert and a bipartisan group of congressmen and senators. But it is expected to fail without Bush's support.

Sean McCormack, a Bush administration official, says the administration's approach to climate change is being totally reassessed. “Other parties should not make any assumptions about what US policy will be until the review is complete,” he says.

International leaders took the unusual step of commenting on Bush's decision. Margo Wallström, environmental commissioner for the European Union, said in a statement that she was concerned about Bush's characterization of the science of global climate change. And Klaus Toepfer, executive director of the United Nations Environment Programme, said in a speech in Denmark that he doubted there could be an effective global response to climate change without US leadership.