In 2001, Cambridge University Press published The Skeptical Environmentalist: Measuring the Real State of the World by the Danish statistician Bjørn Lomborg. The book triggered a firestorm of criticism, with many well-known scientists denouncing it as an effort to "confuse legislators and regulators, and poison the well of public environmental information." In January 2002, Scientific American published a series of articles by five distinguished environmental scientists contesting Lomborg's claims. To some observers, the ferocity of the attack was surprising. Why so much furor over a book that claims to have good news about our environmental condition?

Lomborg portrays himself as an "left-wing, vegetarian, Greenpeace member," but says he worries about the unrelenting "doom and gloom" of mainstream environmentalism. He describes what he regards as an all-pervasive ideology that says, among other...