A leading researcher at the heart of a raging debate over leaked e-mails about the validity of climate change said Friday that his work has been manipulated and that he is the target of a "smear campaign" by global warming naysayers.
"It's an 11th-hour smear campaign where words in e-mails were taken out of context," 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.
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The e-mails also appear to discuss efforts to prevent scientists skeptical of climate change from publishing materials in major science journals. The e-mails were obtained from a well-regarded British research unit at the University of East Anglia.
Mr. Mann told reporters that those opposing action on stopping catastrophic changes to the earth's surface caused by global warming "don't have science on their side and have resorted to the smear campaign." The Penn State researcher is best known for his controversial "hockey stick" theory on global warming, which suggests that the past five decades have been the hottest, and that humans are to blame.
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."
President Obama's top science adviser, John Holdren, wrote some of the leaked e-mails and testified on his work Wednesday at a congressional hearing on global warming.
Mr. Holdren said that some of Mr. Mann's methods are unconventional, but agreed with the researcher's conclusion that the world is warming.