Mark Thoma writes,

Paul Krugman tackles the trashing of science by oil companies, Exxon in particular, to cloud research pointing to global warming.

He quotes from the Krugman piece, which appears to be a typical type M argument.

At the movies this weekend, I saw a trailer for An Inconvenient Truth, described in the review as

the gripping story of former Vice President Al Gore, who became interested in this startling issue while at college 30 years ago, and now devotes his life to reversing global warming. Traveling the world, he has built a visually mesmerizing presentation designed to disabuse doubters of the notion that climate change is debatable. The heart of Davis Guggenheim’s film is this elegant multimedia lecture itself, where Gore indisputably correlates CO2 emissions with exponentially rising temperatures, already responsible for dramatic climactic shifts like ice-cap melting, drought, and rising sea levels. Interwoven with this riveting public address are intimate moments revealing the poetic, searching side of Gore as he struggles to define his purpose in the aftermath of the 2000 election. This is activist cinema at its very best, for it serves to popularize and demythologize a problem long obscured by those most threatened by the solution. With humor and searing intelligence, Gore outlines crucial steps we must take to avert impending disaster and proves that inaction is no longer an option–in fact, it’s immoral.

My concern is with how “scientific consensus” is reached. In economics in the 1960’s, there was a “scientific consensus,” embedded in sophisticated macro-econometric models, that inflation reflected a competition over income shares, and that government policies to interfere with wage- and price-setting were the solution. Milton Friedman’s contrary views were outside the “scientific consensus.”

By 1985 or so, the “scientific consensus” had shifted, in part because policies based on that consensus were tried in the 1970’s, leading to the worst macroeconomic performance of the post-war period.

By the 1990’s, large macro-econometric models had pretty much disappeared from the economics literature. The problem with macro-econometrics is that the models continually broke down out of sample. That is, a model estimated through 1969 would work terribly in predicting the early 1970’s. A model estimated through 1975 would work terribly in predicting the late 1970’s, and so on.

Milton Friedman’s dissenting views of 1967 are close to the consensus views today.

I wish that climate-change models did not remind me so much of macro-econometric models. I wish that the contempt that the Left expresses for dissenting views in climate science did not remind me of the contempt that the Left expressed for Milton Friedman. And I wish that the debate over climate change were being waged over substance, rather than with type M arguments and on film. Movies are a propaganda medium, not an information medium.

I worry that the environmentalists are motivating themselves to stage a religious war over global warming. My guess is that mankind will not be well served by such a religious war.