"Any scientist now, in any field, is going to be far more careful in what they put in personal emails," said Mann, speaking to press at the American Geophysical Union Fall Meeting in San Francisco. "Scientists will be much less willing to engage in vibrant and passionate discussions with their colleagues through email. That could stymie the process of science. Science thrives in open communication."

Mann believes scientists will end up spending more time writing and redraughting their emails to ensure that their meaning is watertight and cannot be misrepresented, in case the correspondence later becomes public.

"There is no evidence of anything even verging on inappropriate scientific behaviour [in the leaked emails], but it sets a very chilling precedent," he said. "Have we really gotten to the point where it's ok to break into people's personal correspondence and take these words out of context?"

According to Mann, the deniers don't have science on their side anymore but have chosen instead to engage in a smear campaign. "There is no level to which the climate denial movement won't stoop," he added. "This is a new level of dishonesty. They are not even attempting to engage in legitimate debate - it's a new low in the climate change denial effort."

Mann believes that the forthcoming investigations and inquiries will "in the end find that nothing is wrong here other than people speaking openly in emails as you might expect them to - there's nothing in any of these emails that calls into question the science."

And the affair is a "false controversy that has been manufactured… to make science look like it's been compromised; it's an effort to cloud the debate and distract the public and policymakers at the crucial time when they are meeting in Copenhagen".

Mann hopes the leaks will have had no impact at the COP15 negotiations. "I feel confident that policymakers are up to speed with the science," he said. "I think they might feel insulted that some would try to manipulate them - I think they will see through that", particularly given the suspicious nature of the timing of the leaks.

Earlier in the day, in a presentation on communicating about climate change, Mann had spoken of the "stiff headwind we must fight of a concerted disinformation effort designed to confuse the public about the nature of our scientific understanding of the problem". The abstract he submitted in August for today's presentation seems prescient now, given the events of Climategate.

During his talk, Mann detailed how the media alone cannot be expected to adequately defend climate science and scientists. "It's not their job," he said. "Scientists must play a key role in combating the disinformation effort, presenting a positive case for science and turning lemons into lemonade, while readily acknowledging the real uncertainties and distinguishing them from manufactured ones."