A scientist who has long disagreed with the dominant view that global warming stems mainly from human activity has resigned from a panel that is completing a report for the Bush administration on temperature trends in the atmosphere.
The scientist, Roger A. Pielke Sr., a climatologist at Colorado State University, said most of the other scientists working on the report were too deeply wedded to particular views and were discounting minority opinions on the quality of climate records and possible causes of warming.
"When you appoint people to a committee who are experts in an area but evaluating their own work," he said in an interview, "it's very difficult for them to think outside the box of their research."
Administration officials said the resignation would not affect the quality or credibility of the report, a draft of which is being finished in the next few weeks.
The report, the first product of President Bush's 10-year climate change research program, is likely to be closely scrutinized by climate scientists and environmental and industry groups for any sign of bias or distortion.
Its main focus is to explore why thermometers at the earth's surface, especially in the tropics, have measured more warming than has been detected by satellites and weather balloons in the troposphere, the layer of the atmosphere up to where jetliners cruise.
Dr. Pielke contends that changes in landscapes like the spread of agriculture and cities could explain many of the surface climate trends, while most climate experts now see a clear link to accumulating emissions of heat-trapping gases like carbon dioxide.
James R. Mahoney, an assistant secretary of commerce and the director of the federal climate research program, said the scientists involved in generating the report were "representative of the broad views" on the questions.
Mr. Mahoney noted that drafts of the climate report would be reviewed by the National Academy of Sciences and were subject to public comment.
"I'm disappointed that Dr. Pielke has chosen to resign over this," Mr. Mahoney said.
Dr. Pielke said he decided to resign after three papers on the troposphere trends were published online on Aug. 11 by the journal Science. The papers said errors in satellite and balloon studies in the tropics explained why earlier analyses failed to find warming in the troposphere.
Several authors of those papers, who are also authors of the coming government report, said at the time that the new findings would be discussed in the report.
Dr. Pielke said those statements were an effort to influence the shape of the final report.
Several authors of those papers denied this, saying the process of creating the reports is intended to be public, while the contents remain confidential for now.
John R. Christy, another author of the coming report who like Dr. Pielke doubts that human-caused warming poses a serious threat, said that while disagreements were normal, the effort to generate the report was improving understanding.
"This process is the worst way to generate scientific information," said Dr. Christy, who teaches at the University of Alabama, Huntsville. "Except for all the others."
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