The scientists were keenly aware of how their work would be viewed and used, and, just like politicians, went to great pains to shape their message. Sometimes, they sounded more like schoolyard taunts than scientific tenets. 

The scientists were so convinced by their own science and so driven by a cause "that unless you're with them, you're against them," said Mark Frankel, director of scientific freedom, responsibility and law at the American Association for the Advancement of Science. He also reviewed the communications.

Frankel saw "no evidence of falsification or fabrication of data, although concerns could be raised about some instances of very 'generous interpretations.' "

Some e-mails expressed doubts about the quality of individual temperature records or why models and data didn't quite match. Part of this is the normal give-and-take of research, but skeptics challenged how reliable certain data were.

The e-mails were stolen from the computer network server of the climate research unit at the University of East Anglia in southeastern England, an influential source of climate science, and were posted online last month. The university shut down the server and contacted the police.

Some of the e-mails mention, were written by or were sent to prominent Boulder researchers at the National Oceanic and Atmospheric Administration, the University of Colorado and the National Center for Atmospheric Research, including senior scientists Tom Wigley and Kevin Trenberth.

Lack of transparency

AP studied all the e-mails for context, with five reporters reading and rereading them — about 1 million words in total.

One of the most disturbing elements suggests an effort to avoid sharing scientific data with critics skeptical of global warming. It is not clear whether any data were destroyed; two U.S. researchers denied it. 

The e-mails show that several mainstream scientists repeatedly suggested keeping their research materials away from opponents who sought it under American and British public-records laws. It raises a science ethics question, because free access to data is important so others can repeat experiments as part of the scientific method.

The University of East Anglia is investigating the blocking of information requests. 

"I believe none of us should submit to these 'requests,' " declared the university's Keith Briffa. The center's chief, Phil Jones, wrote: "Data is covered by all the agreements we sign with people, so I will be hiding behind them."

When one skeptic kept filing FOI requests, Jones, who didn't return AP requests for comment, told another scientist, Michael Mann: "You can delete this attachment if you want. Keep this quiet also, but this is the person who is putting FOI requests for all e-mails Keith (Briffa) and Tim (Osborn) have written." 

Mann, a researcher at Penn State University, told AP: "I didn't delete any e-mails as Phil asked me to. I don't believe anybody else did."

"Culture of corruption"

 The most provocative e-mails are usually about one aspect of climate science: research from a decade ago that studied how warm or cold it was centuries ago through analysis of tree rings, ice cores and glacial melt. And most of those e-mails, which stretch from 1996 to last month, are from about a handful of scientists in dozens of e-mails.

Still, such research has been a key element in measuring climate change over long periods. 

As part of the AP review, summaries of the e-mails that raised issues from the potential manipulation of data to intensely personal attacks were sent to seven experts in research ethics, climate science and science policy.

"This is normal science politics, but on the extreme end, though still within bounds," said Dan Sarewitz, a science policy professor at Arizona State University. "We talk about science as this pure ideal and the scientific method as if it is something out of a cookbook, but research is a social and human activity full of all the failings of society and humans, and this reality gets totally magnified by the high political stakes here."

In the past three weeks since the e-mails were posted, longtime opponents of mainstream climate science have repeatedly quoted excerpts of about a dozen e-mails. Republican congressmen and former vice presidential candidate Sarah Palin have called for either independent investigations, a delay in U.S. Environmental Protection Agency regulation of greenhouse gases or outright boycotts of the Copenhagen international climate talks. They cited a "culture of corruption" that the e-mails appeared to show.

That is not what AP found.

There were signs of trying to present the data as convincingly as possible.

One e-mail that skeptics have been citing often since the messages were posted online is from Jones. He says: "I've just completed Mike's (Mann) trick of adding in the real temps to each series for the last 20 years (from 1981 onward) and from 1961 for Keith's to hide the decline."

Jones was referring to tree ring data that indicated temperatures after the 1950s weren't as warm as scientists had determined.

The "trick" that Jones said he was borrowing from Mann was to add the real temperatures, not what the tree rings showed. And the decline he talked of hiding was not in real temperatures but in the tree-ring data, which was misleading, Mann explained.

But in the end, global warming didn't go away, according to the vast body of research over the years.

None of the e-mails flagged by AP and sent to three climate scientists viewed as moderates in the field changed their view that global warming is man-made and a threat. Nor did it alter their support of the conclusions of the Intergovernmental Panel on Climate Change, which some of the scientists helped write. 

"There is nothing we can do about them aside from continuing to publish quality work in quality journals (or calling in a Mafia hit)."
— Scientist in a March 12, 2003, e-mail about the work of two skeptics. Their paper minimizing the impact of human activity on climate change was eventually discredited when it was found to have been funded in part by the oil industry.

"In an odd way this is cheering news!" — A climate scientist reacts to the death of a climate change skeptic in January 2004.

"Personally, I wouldn't send him anything. I have no idea what he's up to, but you can be sure it falls into the 'no good' category."
— Michael Mann, in a Sept. 2, 2004, conversation about scientific rival Steve McIntyre's requests for data.

 "I can't see either of these papers being in the next IPCC report. Kevin and I will keep them out somehow — even if we have to redefine what the peer-review literature is."
 — Phil Jones, in a July 8, 2004, e-mail to Mann marked "HIGHLY CONFIDENTIAL." In fact, the two papers did appear in the IPCC report, according to the journal Nature.