-->Goodbye, hole in the sky
By Vanessa Holden and Clive Cooksen
Published: September 20 2002 20:10 | Last Updated: September 20 2002 20:10


Scientists are quietly celebrating some good news about the global environment. Two studies published this week suggest that international action to protect the ozone layer in the upper atmosphere is working.

Atmospheric levels of ozone-destroying chemicals, which are being phased out by the 1987 Montreal protocol, are beginning to fall. And researchers predict that the ozone hole may have healed itself completely within 50 years.

Twenty years ago, when scientists working for the British Antarctic Survey detected a gaping hole in the ozone layer more than 10km above the earth's surface, the discovery shocked the scientific world. It meant that more ultraviolet radiation would reach the ground, threatening the health of humans, plants and animals and perhaps affecting climate too.

Much of the news over the past two decades has confirmed these fears. The ozone hole has grown alarmingly during its seasonal appearance over Antarctica during late winter and spring, reaching 28m square km in September 2000.

Areas beneath the hole suffered significant increases in harmful radiation. In one episode, a girl in the Falklands suffered third-degree burns after being exposed to the sun for only 30 minutes. During the 1990s a similar though smaller ozone hole appeared over the Arctic and the ozone layer started to thin even over mid- latitude regions of Europe and north America.

Over the past year, however, atmospheric scientists have lost some of their pessimism about the ozone layer. A study by the UN Environment Programme and the World Meteorological Organisation, released this week, illustrates the new mood of cautious optimism.

It detected"good signs of recovery", though the ozone layer"will remain particularly vulnerable over the next decade even if countries comply with international agreements to protect it".

At the same time, Australian scientists released encouraging findings from the Cape Grim monitoring station in Tasmania, which tracks the changing composition of the atmosphere. The level of ozone-destroying chlorine from chlorofluorocarbons has begun to fall, they say - predicting that the Antarctica ozone hole will start to shrink within five years.

Paul Fraser, chief atmospheric scientist with the Commonwealth Scientific and Industrial Research Organisation, is delighted."This is big news. We have been waiting for this," he says.

Dr Fraser says the findings vindicate the international effort to clamp down on ozone-depleting chemicals, which came into force with the Montreal protocol. This treaty tackled ozone- depleting chemicals such as CFCs - widely used in aerosols, solvents and refrigerants - by banning their use in industrialised countries by 1996 and phasing them out in developing countries by 2010. It was the first time nations had agreed to tackle a global problem before its existence had been scientifically proven.

The first inklings of a threat to the ozone layer came in the early 1970s.

Scientists realised then that CFCs - extremely long-lived molecules - could migrate slowly into the upper atmosphere, where they would be broken down by solar radiation to release chlorine. Through a chemical chain reaction, a single atom of chlorine could destroy myriad molecules of ozone, an unstable form of oxygen.

But the campaign to impose controls on CFCs, which began in the mid-1970s, proved highly controversial.

Industrialists were initially hostile to the prospect of new regulations, believing that the science was too speculative, the economic costs were too great and the technical solutions were out of reach. In the end, however, extensive innovation by chemical companies meant that substitutes for CFCs could be introduced with far less disruption than industry had feared.

Although the Montreal protocol is hailed today - in the words of Klaus Toepfer, UNEP executive director - as"a success story of which we can all be proud", there are still concerns about its effectiveness.

One problem concerns the illegal trade in banned chemicals. Since millions of CFC-dependent refrigerators, air-conditioners and other equipment are still in use around the world, criminals have an incentive to smuggle CFCs across borders. Another threat comes from a range of new chemicals, used in a range of applications including fire extinguishers and cleaning fluids, that have some potential to damage the ozone layer, though they are less dangerous than CFCs.

A big uncertainty is the complex interplay between climate change and ozone depletion. Global warming at the earth's surface may be accompanied by cooling in the upper atmosphere, which would accelerate the chemical processes that lead to ozone depletion. This could postpone the recovery of the ozone layer by as much as 20 or 30 years.

Other events, such as the release of particles into the atmosphere by a volcanic eruption, could also exacerbate ozone depletion, according to this week's UNEP/WMO study.

Yet the central conclusion of the 250 scientists who produced the study is that the Montreal protocol is indeed working.

This success has stiffened the resolve of the inter- national negotiators who are attempting to create an effective regime to tackle global warming.

Admittedly, the problem of climate change is far more complicated and extensive than ozone depletion. Whereas the main impact of the Montreal protocol was felt by a relatively small number of industries, notably chemicals and refrigeration, the attempt to curb greenhouse gas emissions will have an impact on vast numbers of individuals and businesses.

Yet the scientists and policymakers involved in the Montreal protocol are convinced that it offers wider lessons. In the view of Dr Fraser, the latest findings on the ozone hole underline the difference that the inter- national community can make to environmental issues."This shows global protocols can work," he says.


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