The uncertainties of global warming....

There are so many unknowns when it comes to global warming..this is from a speech by Nigel Lawon, former chancellor of the exchequer in the Thatcher government...

So we are left with a double uncertainty. First, while we know that, other things being equal, rising atmospheric concentrations of carbon dioxide will warm the planet, we have no true understanding of how much they will do so. And second, we know that in fact other things are very far from equal. So even if we did know the answer to the first question, we would still be unable to predict what the world's temperature will be a hundred years from now. These uncertainties clearly have a profound bearing on the economics of global warming, and thus on the policies it is sensible to pursue.

For while we can do our best to make an estimate of the cost of substantially decarbonising the world economy, we have no idea of what benefit that will bring in terms of a lower mean global temperature than would otherwise be the case. Not that it is clear, even if we could predict the temperature of the planet a hundred years from now (which we can't), how much economic damage a given rise in temperature would do.

It was to advise governments on these issues that the Intergovernmental Panel on Climate Change was set up in 1988, under the auspices of the UN. The IPCC concludes, on the basis of to say the least very slender evidence, that "most" - note, not all - of the warming that occurred during the last quarter of the 20th century was very likely to be due to the growth of atmospheric carbon dioxide concentrations. But even if - and there is clearly a case for erring on the side of caution - this is so, and even if, as the IPCC blithely assumes, the natural forces that affect the world's temperature in often unpredictable ways can be safely ignored, the policy conclusions which are widely believed to follow from this are very suspect indeed.

Is it really plausible that there is an ideal average world temperature, which by some happy chance has recently been visited on us, from which small departures in either direction would spell disaster? Moreover, while a sudden change would indeed be disruptive, what is at issue here is the prospect of a very gradual change over a hundred years and more. In any case, average world temperature is simply a statistical artefact. The actual experienced temperature varies enormously in different parts of the globe and man, whose greatest quality is his adaptability, has successfully colonised most of it. Two countries that are generally considered to be economic success stories, are Finland and Singapore.

The average annual temperature in Helsinki is less than 5C. That in Singapore is in excess of 27C, a difference of more than 22C. If man can successfully cope with that, it is not immediately apparent why he should not be able to adapt to a change of 3C, when he is given a hundred years in which to do so.