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Retorts

Greenhouse Reality

It is Dr Gray [Retorts, September] who has not kept up with the literature concerning the Greenhouse Effect.

Although there are uncertainties associated with the increase of greenhouse gases and global warming, nevertheless there has been a global warming of 0.5oC during this century. From 1940-1980, temperatures were stable, probably due to sulphate aerosols produced during this period. Now that efforts are being made to reduce sulphur emissions, the sulphate cooling of the upper atmosphere, calculated to be 0.25oC, is not as prominent and the warming trend has continued since 1980.

Computer models produced at the Hadley Centre in Bracknell (UK) have succeeded in accurately reproducing past climates, back to 1860 when accurate records began (New Scientist 26 Nov 94).

At the World Renewable Energy Congress (Reading UK, Sept 94) Sir John Houghton spoke of the increasing evidence for global warming, and his book Global Warming, The Complete Briefing (Lion Press 1995) is available for those interested. At the Congress, Dr J Leggett of Greenpeace presented data showing how the cost of storm damage world-wide has increased exponentially, in real terms, since 1968. The insurance industry is taking global warming seriously, as good a piece of evidence for the reality of the situation as could be required. Money's at stake!

There is now statistically significant evidence for the melting of sea-ice at both poles (New Scientist 12 Aug 95). This will accelerate sea level rises, which have already amounted to about 12cm during this century, and although Dr Gray may live on the hills above Wellington, many of the inhabitants of this planet don't fancy any further rise.

The situation reminds me of the debate which occurred over the dangers of tobacco smoking during the last 40 years. On many occasions I have been assured, between coughs, that cigarettes do not endanger health. I suspect that history is being repeated in the debate over global warming and the Greenhouse Effect. If Dr Gray is right in his assertions that global warming is of no threat, it makes little difference whether we take precautions or not. At the worst we will have learned to be more energy efficient, and our fossil fuel reserves will last a little longer. However if, as most believe, global warming is a threat, and if the developed nations make no efforts to restrain greenhouse gas emissions, then humankind is in for a rough ride.

Dai Redshaw, Dunedin