The
hole in the ozone layer over Antarctica is about to start shrinking
and will close by 2050, Australian researchers say.
Government scientists in Tasmania said scientific data showed the
level of ozone-depleting chlorine in the atmosphere was declining
because of the ban on the use of chlorofluorocarbons (CFCs) in fridges
and air conditioners, agreed under the Montreal Protocol in 1987.
Dr Paul Fraser, the chief atmospheric research scientist with
the Commonwealth Scientific and Industrial Research Organisation,
said: "This is big news. We have been waiting for this. We
think the trend is definite now. It is very significant."
Dr Fraser said that after the ban was adopted, the atmospheric
level of chlorine continued to rise, peaking in 2000. "That
was simply due to old refrigerators and old air-conditioners in
cars," he says.
Since then, the level had stabilised and was now declining, albeit
slowly, Dr Fraser said. He predicted that the hole in the ozone
layer would contract steadily from about 2005 and disappear by
mid-century, although the ozone would be vulnerable for a decade.
Under the Montreal Protocol, developing countries committed themselves
to halving consumption and production of CFCs by 2005 and achieving
an 85 per cent cut by 2007. The hole in the ozone layer, which
protects Earth from the Sun's ultraviolet rays, was first detected
nearly 30 years ago. It was then three times the size of Australia,
itself covering nearly 3 million square miles.
(Agencies)
Updated: 2002-09-20 01:00
直到2000年以后，氯氣含量才停止增加并呈現(xiàn)緩慢下降的趨勢(shì)。弗雷澤博士預(yù)測(cè)說，臭氧空洞將于2005年開始收縮變小，直到本世紀(jì)中期被完全填滿，但填滿后仍有十年屬于比較容易被破壞的過渡期。