Climate-change skeptics, fired up by the controversy over a series of British scientists' e-mails, are putting President Obama on notice: Don't commit the United States to any long-term goals at next week's climate summit in Copenhagen.
One of the strongest such warnings has come from a member of the president's own party, Sen. Jim Webb of Virginia.
"Recent statements by Special Envoy for Climate Change Todd Stern indicate that negotiators may be intending to commit the United States to a nationwide emission-reduction program," Mr. Webb wrote in a letter to the president.
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"As you well know from your time in the Senate, only specific legislation agreed upon in the Congress, or a treaty ratified by the Senate, could actually create such a commitment on behalf of our country."
Some prominent skeptics are going further, arguing that Mr. Obama should not attend the summit at all.
"Every time he attends, he will give something away," said Fred Singer, a professor emeritus of environmental science at the University of Virginia.
"He is expected to bring presents. If he doesn't attend, less will be expected of us, and that is better," Mr. Singer said. "My hope is that the U.S. Senate will not approve any kind of treaty obligation."
Referring to the British e-mails, he said, "We finally have proof of what we have always suspected - that these guys have been fudging the data. My hope also is that there will be an independent science panel who will go over their data and methods and come up with a report that will set the matter straight."
Whatever one's views on the science of climate change, the so-called Climategate scandal could not have come at a worse time for those who hope to see the world's major industrial countries take strong action at the Copenhagen climate summit, which opens Monday with more than 10,000 participants.
Contained among thousands of e-mails released last month from the University of East Anglia's Climate Research Unit are a number of remarks that suggest the scientists there distorted some data to conform to their expectations. The center's chief has stepped down pending an investigation of the e-mails.
Prominent climate scientists insist that the e-mails do not change what they see as an urgent need to reduce the emission of greenhouse gases, and there is little likelihood that the outcome of the climate summit will be affected.
"The body of evidence that human activity is a prominent agent in global warming is overwhelming," said Harvard professor James McCarthy, who chairs the American Association for the Advancement of Science.
"The content of these few personal e-mails has no impact whatsoever on our overall understanding that human activity is driving dangerous levels of global warming," he said in a letter this week to Sen. Barbara Boxer, California Democrat, which was cited in the Boston Globe.
The skeptics, however, have seized on the leaked e-mails as long-awaited vindication of their views and are using their disclosure to argue against the administration's participation in the summit.
"It's getting into a card game without a lot of cards," said Patrick Michaels, a senior fellow at the Cato Institute and retired University of Virginia environmental sciences professor. He portrayed Mr. Obama's decision to attend the summit as a "panicked" response to the e-mails' release.
The leaks also have left the American public more confused about whether to believe in global warming, according to a Rassmussen Reports telephone survey released on Thursday.
It found that 46 percent of Americans say global warming constitutes a major problem, with 36 percent disagreeing and 18 percent undecided. Fifty-nine percent, however, contend it is at least somewhat likely that some scientists could have falsified their research in an effort to bolster global-warming claims. Thirty-five percent said it's very likely, while 26 percent said not very or not likely at all that the researchers falsified their work.
The Rasmussen poll also found little confidence among Americans in climate research carried out under the auspices of the United Nations. Just 22 percent of Americans said they consider the global body a reliable source for global-warming information, while 49 percent said it is not reliable. Another 29 percent said they weren't sure.