THIS is one of the most valuable books on public policy—not merely on environmental policy—to have been written for the intelligent general reader in the past ten years. Its target is environmental pessimism, the defining mood of the age. By the end, fair-minded readers will find that most of the concerns they had about the future of the planet have given way to fury at the army of dissembling environmentalists who have dedicated themselves to stirring up panic by concealing the truth.

The idea that the world is heading for ruin seems to be taken for granted by almost every television news programme and newspaper, whether the subject is poverty in Africa, global warming, trends in population, traffic jams in Manchester or a spell of bad weather in Detroit. This gloom directly affects the debate on environmental policy, of course, but its influence goes wider than that. It supports the conviction that capitalism is self-destructive, and so lurks in the background of many an economic debate, broad or narrow. Yet this faith in looming environmental disaster, Mr Lomborg shows, is false.

The author is a professor of statistics at the University of Aarhus. His expertise lies in numbers and sources. So in “The Skeptical Environmentalist” he examines the views of the world's leading environmental pressure groups simply by consulting the sources (if any) they cite, together with other relevant literature. Again and again, he finds that the pessimists' claims are falsified not merely by the available scientific evidence but by their own quoted sources.

The accumulating power of the book lies in the sheer toll of carefully documented examples. Bearing that in mind, consider just one, to get a flavour. The Worldwatch Institute has claimed that the world's forests have “declined significantly” in recent decades. In fact, the longest data series, gathered by a United Nations agency, shows that global forest cover grew between 1950 and 1994. In particular, the institute noted, Canada is losing 200,000 hectares of forest a year. On checking the quoted source, Mr Lomborg finds that Canada's forests grew by 174,000 hectares a year. This is representative: the book exposes countless errors, evasions and distortions of this sort.

As well as insisting on statistical probity, Mr Lomborg brings another intellectual virtue to the task: an interest in feasible alternatives. On global warming, for instance, he shows that standard claims about the extent of the problem are deliberately exaggerated (though he does not deny that some global warming is going on); beyond that, however, he asks about costs. The cost of preventing warming could easily outweigh the harm caused by letting it happen, and by a very wide margin, depending on the method. If concern for developing countries came first (and that is where global warming will cause most harm), there would be much better ways of spending money than on schemes such as the Kyoto plan. Providing universal access to clean water would do more good than the tiny cut in warming envisaged by Kyoto, at about a fifth of the price.

Mr Lomborg is not the first to take a stand of this sort against the excesses of the environmentalist movement. He follows in the footsteps of the late Julian Simon, one of the 20th century's unsung heroes of economics. (Mr Lomborg generously acknowledges Simon's role.) But Simon was a quirky conservative, and therefore ignored by the mainstream media. Mr Lomborg is a soft-left Greenpeace defector, a photogenic blond Dane, a charming self-promoter who understands the importance of, as he puts it, “being seen to be nice”. That makes him a story. His findings have caused a furore in Scandinavia and, with this book, show signs of being noticed elsewhere. Good. More power to him. “The Skeptical Environmentalist” is a triumph.

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