Consensus can be wrong. So warned The New York Times in a science section piece on Oct. 9. "Diet and Fat: A Severe Case of Mistaken Consensus" reviewed the history of our belief that dietary fat was as big a health risk as smoking. Surgeon General C. Everett Koop declared as much in 1988. He was speaking not for himself but for the scientific community, which was nearly unanimous in fingering fat as the cause of heart disease and cancer.

The trouble was, study after study failed to prove the hypothesis. It was a case, the Times explains, of "informational cascade" -- a phenomenon in which groups tend to reach false conclusions because individuals often assume that the majority must be right.

Thank you, New York Times. It's a good cautionary tale about human psychology and one the Times ought to take to heart in its coverage of the global warming question. That is the issue we are currently "cascading" to conclusions about, the Times no less than anyone else. The climate of opinion on climate is dogmatic verging on hysterical. Kids are coming home from school in tears having been taught that the world they were born into will soon descend into a nightmare of massive storms, swamped cities and dying animals.

The dying animals is a big favorite in the schools, particularly the stranded polar bear on an ice floe searching for land. That one even got to my worldly sons. So I was particularly happy to have Bjorn Lomborg's new book, "Cool It: A Skeptical Environmentalist's Guide to Global Warming," on hand.

Lomborg does not deny that global warming is happening, nor that it is the result of human action. But he does apply a necessary damper to the white-hot rhetoric and scare mongering of the global warming fanatics. A political scientist by training and an economist by outlook, the man The Wall Street Journal called the "golden-haired Dane" applies common sense and cost/benefit analysis to a subject brimming with emotion and unreasoning fear.

Along the way, he debunks some of the myths. Pace Al Gore it seems that of the 20 subpopulations of polar bear, one or possibly two are declining in population. But more than half are stable, and two are increasing. Actually, the world population of polar bears has mushroomed over the past several decades, from some 5,000 in the 1960s to about 25,000 today, due to stricter regulation of hunting. As for those two subgroups that are declining in population, they live in regions in which the temperatures have actually been dropping over the past 50 years, whereas the subgroups that have seen an increase in population live in areas that have been getting warmer.

The polar bear example is instructive because the solution being urged upon us to save the bears is a massively expensive but ultimately nearly fruitless effort to cut greenhouse gas emissions. If we follow Kyoto or some other framework, we can at best save .06 bears per year. "But," Lomborg writes, "49 bears from the same population are getting shot every year, and this we can easily do something about."

It's the same with climate change writ large. Drastically reducing greenhouse gas emissions is hardly cost free. To achieve the goals outlined in the Kyoto accords, for example, would cost the world $180 billion annually for 50 years.

Examined rationally, it is clear that while global warming will do harm to some parts of the world, it will also do good to others. Might not the money be better spent mitigating the negative effects of a warming planet?

Lomborg's book focuses on trade-offs. If we're going to spend a fixed amount of money to improve the world, what makes the most sense? Or to put it another way, which dollar spent produces the greatest benefit? According to a group of economists (including four Nobel Prize winners) who examined this question in 2004, the answer was clear. One dollar spent fighting HIV/AIDS produced $40 in social benefits. One dollar spent on fighting malnutrition yields about $30 in social benefits. Other efforts, like ending agricultural subsidies in the wealthy countries and ensuring worldwide free trade, would net a $15 benefit for a one-dollar cost. Cutting CO2 emissions, by contrast, yields between 2 and 25 cents per dollar invested.

The consensus is wrong on global warming. Wonder when The New York Times will figure it out? In the meanwhile, Lomborg points the way toward clear analysis.