Michael Shermer was a well known global warming skeptic until he publicly changed his position in the June 2006 issue of Scientific American. He says: "Nevertheless, data trump politics, and a convergence of evidence from numerous sources has led me to make a cognitive switch on the subject of anthropogenic global warming. My attention was piqued on February 8 when 86 leading evangelical Christians--the last cohort I expected to get on the environmental bandwagon--issued the Evangelical Climate Initiative calling for 'national legislation requiring sufficient economy-wide reductions' in carbon emissions."
Then I attended the TED (Technology, Entertainment, Design) conference in Monterey, Calif., where former vice president Al Gore delivered the single finest summation of the evidence for global warming I have ever heard, based on the recent documentary film about his work in this area, An Inconvenient Truth. The striking before-and-after photographs showing the disappearance of glaciers around the world shocked me out of my doubting stance. [...]
Because of the complexity of the problem, environmental skepticism was once tenable. No longer. It is time to flip from skepticism to activism.
Short bio of Michael Shermer via Wikipedia:
Michael Shermer (born 1954) is a science writer, historian of science, founder of The Skeptics Society, and editor of its magazine Skeptic, which is largely devoted to investigating pseudoscientific and supernatural claims. Shermer also produces and co-hosts the 13-hour Fox Family television series, "Exploring the Unknown," and is a monthly columnist for Scientific American magazine.
::The Flipping Point