Other pundits criticized Mann and colleagues for agreeing to shun the journal Climate Research after it published work by climate-change skeptics. Mann said the particular article was bad science and was "polluting" the journal.
Since the e-mails became public, Patrick Michaels, a climate researcher at the Cato Institute, has criticized Mann in the editorial pages of the Wall Street Journal. Michaels cited an exchange in which Mann asked Phil Jones of the University of East Anglia's Climate Research Unit to nominate him to become a fellow of the American Geophysical Union, the country's major group for earth scientists. Michaels called this unethical. Several AGU fellows who work outside the climate community said they saw nothing wrong with asking someone for a nomination.
Michaels also flagged an e-mail in which Mann discussed a reference he was writing for Jones. In that, Mann misstated a number called the "h index," which measures a scientist's productivity and influence.
Mann said it was just an error in a hastily typed private e-mail, in which he meant to say 52 but instead said 62. He produced a copy of the official letter, in which he got the number correct.
He said he was surprised that Michaels would castigate him over a typographical error. "They've sunk to a new low," Mann said of the e-mails. "This shows they've given up legitimate debate."
There is still much debate over how big a role human activity plays in the current warming trend, and how the future will be affected. Climate science - and earth science in general - is not expected to make the kinds of sharp predictions that chemists and physicists can make with repeated experiments. "It would be nice if we could do controlled experiments," Mann said. "But we have only one Earth."
Contact staff writer Faye Flam at 215-854-4977 or fflam@phillynews.com.
