The little boy who cried “wolf” was finally proved right and was gobbled up as punishment for his earlier pranks. Malthusians have been crying wolf for a couple of centuries. But in global warming they may well have seen a real one. It would be wrong to say their warnings are being ignored. But they are certainly not receiving much practical attention. The Kyoto protocol now covers a mere 30 per cent of emissions, while its hard limits cover just 8 per cent. Is global warming a wolf at our door?

The argument that it is starts with the observation that some atmospheric gases generate a greenhouse – or warming – effect. This is an excellent thing since they make the earth’s surface temperature about 30ºC warmer than it would otherwise be. But, as concentrations of greenhouse gases rise, so will the the temperature (albeit only if other things remain equal). This, goes the argument, is what is happening.