The recent publication of The Skeptical Environmentalist, a book by Bjrn Lomborg (Cambridge University Press, 2001), ignited an international controversy. His message was widely publicized in the popular media and championed by political commentators traditionally opposed to environmentalist policies. Outraged voices within the mainstream scientific community quickly answered, however, that Lomborgs work was deeply flawed. In its January 2002 issue, Scientific American published the feature \"Misleading Math about the Earth,\" in which four environmental expertsStephen Schneider, John Holdren, John Bongaarts and Thomas Lovejoycriticized The Skeptical Environmentalists arguments on global warming, energy, overpopulation and biodiversity. Lomborg has since written a detailed online rebuttal to our feature; we also have some responses to that rebuttal.