More than 200 years later, for the second time in less than a decade, the 'warmth of the sun's rays' may be giving the world a vital early warning.
Scientists at the British Antarctic Survey (BAS), which discovered the ozone hole in 1985, now believe that 'a dangerous warming' is first becoming evident in the frozen continent. Flowers and grass, as we reported last week, are spreading explosively in the north of Antarctica. More than two-thirds of the 2,000 square-kilometre (770 square-mile) Wordie Ice Sheet, has melted away in the past 30 years: the BAS warns that other sheets face similar 'catastrophic disintegration'. And since the Seventies, the Antarctic summer has lengthened by 50 per cent.
Half a world away, the shrinking band of undisturbed tropical rainforest that encircles the globe, has, says another group of scientists, caught 'the equivalent of a fever'. Researchers at the Missouri Botanical Gardens have found that trees in forests in Australia, South-east Asia, Africa and Central and South America, are growing and dying more rapidly than in the past. The most likely cause, they say, is a build-up of carbon dioxide - the gas emitted from burning oil, gas and coal - that threatens to heat up the planet, raising sea-levels and causing harvests to fail.
Coral reefs along the coasts of more than 20 countries are dying because of rising water temperatures. Extraordinary warming has been measured recently across the Atlantic, Indian and Pacific Oceans, in the Mediterranean and Caribbean Seas and in the Arabian Gulf. European glaciers have shrunk more than at any time in the last 5,000 years, providing, says the United Nations Environmental Programme, 'independent evidence of global warming'. Seven of the eight warmest years on record have occurred since 1980, and this year - with sweltering summers from Toledo to Tokyo - is set to join them.
All of these diverse and disturbing phenomena are consistent with global warming. The evidence is mounting, and even cautious scientists, like those at the BAS, are beginning to believe it is happening. Ten days ago, the official Inter governmental Panel on Climatic Change (IPCC), representing 2,500 top scientists and experts world-wide, finalised a report to be published next month concluding that the world's climate is seriously at risk. Sir John Houghton, chairman of the group that drafted the report, concludes in his recent com prehensive book, Global Warming, the Complete Briefing: 'The rate of change is likely to be larger than the Earth has seen at any time during the past 10,000 years.'
Why are we so unconcerned? It has become as fashionable to deride global warming as it once was to shiver at the perils in prospect. A Department of the Environment survey found this month that concern about global warming has fallen heavily since 1989.
As a species, we have short attention spans. If predictions are not quickly realised, we come to disbelieve them then often fail to notice when they do come true. Take the widespread forecasts 20 years ago that the silicon chip would put people out of work. Alarmed at first, we grew to discount the warnings. Only now, after half a generation of mass un employment, do we realise that the forecasts were right.
Our scepticism over global warming was reinforced by a natural phenomenon. In June 1991, Mount Pinatubo, a volcano in the Philippines, exploded, throwing 20 million tons of sulphur into the upper atmosphere. Over the next two years this screened out some of the sun's radiation, and temperatures dropped. It was hard to believe in a warming world. In fact, the eruption showed that the weather does respond to pollution. And 1992, the year most affected, was still the 10th warmest on record.
And then there was the effective campaign by energy industries and oil-producing countries - and some politicians and newspapers - to discredit the warnings. They drew on the views of a relatively small group of dissident scientists who challenged the consensus. Their objections - for example, that the computer models of the world climate and the effect of pollution on it were crude - have now been largely confounded. These programs are now much more sophisticated, accurately predicting, for example, the effect of the Mt Pinatubo eruption.
More substantially, objectors have argued that sulphur pollution from power stations, factories and car exhausts will, like the volcanic emissions, counteract any heating of the climate. This looks good in theory, but there are two practical problems. The first is that the sulphur is concentrated over indus trialised areas, while the pollution that causes global warming is spread out evenly - so instead of balancing each other, the two pollutants may work together to disturb the climate, making things worse. The second is that the world is rightly reducing sulphur emissions which cause acid rain: Europe has just agreed to an 80 per cent cut by 2010. As the sulphur disappears, the warming will speed up.
And while the arguments of global warming sceptics look thinner, other researchers believe that the consensus is too complacent. One survey of IPCC scientists showed that almost half believed that the danger was graver than the official reports allowed. New satellite data show that the West Antarctic Ice Sheet is discharging ice, rather than accumulating it, as the IPCC assumes. The tropical rainforest 'fever' suggests that the trees are absorbing less of the polluting carbon dioxide than the IPCC believes.
Sensing that public concern has diminished, governments are increasingly dragging their feet even as scientific evidence accumulates. A UN negotiating conference of 150 countries in Geneva this month agreed that existing international efforts were 'inadequate' but did nothing to strengthen them, even though the main actions to combat climatic change - conserving energy, preserving and increasing tree cover - would be essential even if there were no danger to the climate.
Last week an alliance of the world's small island nations - several of which are due to disappear altogether as sea levels rise - formally tabled a draft treaty which would bind industrialised countries to cut carbon dioxide emissions by 20 per cent by the year 2005. It is a perfectly practicable target. Several developed nations have endorsed it in principle, and earlier this month the Environment Committee of the European Parliament did the same. But with Britain and other countries opposing it, and with a general lack of political interest, it stands little chance of being agreed.
Yet just 10 years ago the chances of international action to phase out the chemicals that deplete the ozone layer looked even bleaker - and now they are rapidly being abandoned. The catalyst for the abrupt turnabout was the British Antarctic Survey's discovery of the ozone hole. We must hope that their discovery of the greening of Antarctica may precipitate similar change.
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