A leading researcher at the heart of a raging debate over leaked e-mails about the validity of climate change said Friday that his words have been manipulated and that he is the target of a "smear campaign" by global warming naysayers.
"It's an 11th hour smear campaign where they've stolen personal e-mails from scientists, mined them for single words or phrases that can be taken out of context and misrepresent what scientists are saying," said Michael Mann, director of Pennsylvania State University's Earth Systems Science Center, in a teleconference Friday with reporters.
Mr. Mann's research has been aired over the Internet following a security breach in which thousands of e-mails between prominent American and British climate-change scientists were stolen. Global warming skeptics say the private correspondence could prove that climate data have been hoarded and manipulated by leading climate scientists to overstate the case for human-caused global warming.
In light of the e-mail disclosure, Mr. Mann's research methodology has come under question. But he defended his methods.
"I've done nothing wrong; I have nothing to hide; I think my record stands for itself," he said.
The e-mails also appear to reveal efforts to prevent scientists skeptical of climate change from publishing materials in major science journals. The e-mails were stolen two weeks ago from University of East Anglia, a well-regarded British research unit.
The Penn State researcher is best known for his "hockey stick" theory of global warming, which suggests that the past five decades have been the hottest and that humans are to blame.
President Obama's top science adviser, John Holdren, wrote one of the leaked e-mails and testified on climate change science Wednesday at a congressional hearing on global warming.
Mr. Holdren said that some of Mr. Mann's methods are unconventional, but agreed with his conclusion that the world is warming.
As a result of the breach, Penn State officials are looking into Mr. Mann's e-mails. University of East Anglia officials are also investigating the breach and a top researcher there has temporarily left his post while the probe proceeds.
Mr. Mann said he welcomed the inquiry and thinks Penn State officials are simply "researching information to determine if an investigation is necessary."
One of Mr. Mann's e-mails read: "I think we have to stop considering 'Climate Research' as a legitimate peer-reviewed journal.… We also need to consider what we tell or request of our more reasonable colleagues who currently sit on the editorial board."
Mr. Mann defended his statements on the call, saying: "There was an editor who appeared to be in essence gaming the system to allow through papers that did not meet the basic standards of science simply because they expressed a contrarian viewpoint about climate." He added that there is nothing wrong with skeptical science being published, but in this case, the basic standards of quality had been compromised.
Mr. Mann said that those advocating inaction on stopping catastrophic changes to the earth's surface caused by global warming "don't have science on their side so they've turned to this last-minute smear campaign."
Climate skeptics and some lawmakers have seized on the e-mails as ammunition in their fight against climate change legislation pending on Capitol Hill. They say that the allegedly manipulated data shows that the science behind climate change is not sound.
"The people who are saying that they don't trust scientists now have made the same, precise statements for two decades and they simply latch on to whatever recent thing they can find and misrepresent it to say the same thing," Mr. Mann said.