Paul Johnson explains how global warming evolved from unproven theory to an industry that supports tens of thousands

When I was an undergraduate the philosopher I studied most carefully was Karl Popper, especially his writings on the evaluation of evidence and criteria to distinguish a genuine scientific theory from a false one. He made two key points. First, a theory must include the falsifiability principle. It must be susceptible to empirical tests and, if it fails to meet them, be scrapped. He gave as an example of a genuine theory Einstein's General Relativity of 1915. Einstein insisted that it must survive three practical tests, and if it failed any one of them be dropped as untrue. In fact it passed triumphantly all three, beginning in 1919, and many other since.

Popper argued that prima facie evidence of a bogus theory was the practice of altering or enlarging it, by its authors, to accommodate new evidence since its original formulation. This, he argued, had happened in the case of Marxism and, still more, Freudianism. Scientific theories, he argued, must be very precise and scientific to be of any use. Marxism and Freudianism were just portmanteau notions into which virtually any kind of phenomena could be made to fit. Hence Marxism led to political and economic disaster areas like the Soviet Union, and Freudianism to a stupendous waste of time and money.

It is a pity Popper did not live to see that Global Warming fit perfectly into his model of a pseudo-theory. It is vaguely and imprecisely formulated. It fails the falsifiability test, because all new evidence is made to fit by enlarging the theory. When originally formulated in the 1980s, Global Warming produced by man-made emissions would lead, it was argued, to much higher temperatures and desiccation. There would be a huge drop in rainfall and an imperative need to build seawater desalination plants. I recall an unusually dry summer (1987) in the English Lake District, normally rainy, was triumphantly presented as "absolute proof" of the theory. This autumn, the Lake District had an unusually wet spell, culminating in floods that engulfed the delightful town of Cockermouth, where Wordsworth was born. This was pounced upon by Global Warming "experts" as "absolute proof" of their theory, and paraded as such in Copenhagen.

The fact is that the theory has now been expanded to include any unusual form of weather, anywhere. Hot summers, warm winters -- global warming. Cold weather at an unusual time of year -- global warming. Drought, storms, floods -- global warming. No snow on the ski slopes, sudden snow, out of season snow, very heavy snow -- global warming. Of course in countries like Japan or the UK, where unusual, unpredictable, and tiresomely variable weather is the norm (it was first commented on in the UK by the Venerable Bede in the eighth century), the public does not swallow global warming, and polls show majorities of 55 to 60 percent reject it.

Of course vested interests accept it. It is regarded as a splendid way of damaging the American economy, by the same kind of left-wing intellectuals who supported the Club of Rome in the 1960s, which argued that world resources were on the brink of exhaustion. It is a form of pantheism and a useful emotional outlet for people who have renounced Judeo-Christianity. If someone is anti-American, left-liberal, and atheist, it is virtually certain he (or even she: women are notoriously more skeptical about it than men are) is a Global Warmer.

THEN AGAIN, GLOBAL WARMING NOW HAS a powerful, worldwide institutional substructure. If a media outlet has an environment correspondent, or a university a Department of Climate Studies, or a government a Ministry of Global Warming, those involved are certain to be not just believers but fanatical propagandists for the cause. Their livelihood depends on it. I calculate that the lobby now includes over 20,000 full-time, well-paid professionals whose entire life is spent in pushing "proofs." The existence of this enormous phalanx of well-placed, articulate enthusiasts has inevitably led to the capture of powerful institutions -- in Britain, for instance, the Meteorological Office, the Royal Society, and the BBC, together with many universities and newspapers. It used to be supposed that scientists, or those calling themselves such, were incorruptible and guided purely by genuine convictions based on objective evidence. But scientists behave just like politicians if the pressure and prizes make it worth their while to conform.

So vast sums of money will continue to be spent on an unproven and unprovable theory, predicting a global catastrophe from the realms of fantasy. The money could be much more profitably spent on space exploration. This is a genuine science and could turn out to be useful, even vital.