President George Bush’s decision to have the United States abandon a responsible position on reducing carbon dioxide emissions, a contributor to climate change, makes more extreme cuts in emissions inevitable a few years from now and greatly diminishes the U.S. role in establishing international standards to meet this widely accepted problem.

The conclusions of scientists studying global warming now may differ in degree but not, with rare exception, in the overall trend of a human contribution to the gases that are changing the earth’s atmosphere, leading to the melting of the Antarctic ice cap and causing more severe weather worldwide. The United States produces one-fourth of these gases, and coal- and oil-fired power plants are an important reason for this. That’s why in September in Saginaw, Mich., Mr. Bush said, “With the help of Congress, environmental groups and industry, we will require all power plants to meet clean air standards in order to reduce emissions on sulfur dioxide, nitrogen oxide, mercury and carbon dioxide within a reasonable period of time.”

And it is why Christine Whitman, head of the Environmental Protection Agency, acted as if those words meant something and that the Bush administration would support the Clean Energy Act. But like his clumsy overriding of Secretary of State Colin Powell on the question of North Korea, President Bush issued a letter this week to four senators reversing course and leaving his cabinet member looking ill informed.

Earlier this year, President Bush asked the international negotiators on climate change to delay a conference set for spring until early summer so that the administration could prepare for the event. The negotiators agreed, but there is little point now in their waiting for a U.S. representative to tell them the world’s gasiest nation doesn’t want any standards on carbon dioxide. And President Bush’s argument that a decade long phase-in of cleaner natural gas instead of coal or oil would lead to higher prices makes little sense in the face of the enormous costs associated with climate change.

Congress can play a constructive role in getting the United States back on track. Sen. Olympia Snowe is a lead sponsor with Sen. Jim Jeffords on the bipartisan Clean Energy Act. Rep. Tom Allen last year introduced a similar measure in the House, the Clean Power Plant Act, and also won bipartisan support. He plans to introduce it again this year and, despite the new position by the president, it deserves full congressional support. After extensive debate last year on the issue of climate change, Congress came to the proper conclusion that cleaner sources as well as sensible conservation goals were the most cost-effective way to address this air-pollution issue. Until this week, members thought they had the White House on their side, too.

Closing the Clean Air Act loophole that allows power plants to produce emissions all out of proportion with their value should be a priority in Washington. Mr. Bush stumbled with this latest decision but can correct it by reviewing both the science and the support for this important environmental limit.