MAY BE RECORD SIZE
The ozone hole over the Antarctic is growing at a rate that suggests it could be headed for a record size this year, Australian scientists said on Friday.
A study by Australian Antarctic bases attributed the development to colder temperatures in the stratosphere where the ozone hole forms.
"The growth at the moment is similar to 2000 when the hole was a record size," Australian Antarctic Division scientist Andrew Klekociuk told Reuters on Friday.
Ozone is a protective layer in the atmosphere that shields the Earth from the sun's rays, in particular ultraviolet-B radiation that can cause skin cancer, cataracts and can harm marine life.
In 2000, NASA said the ozone hole expanded to a record 28.3 million sq km (10.9 million sq miles), three times the size of Australia or the United States, excluding Alaska.
"This is in contrast to the situation in 2002 when unusually warm conditions produced the smallest ozone hole since 1988," Klekociuk said.
The ozone hole in 2003 presently covers all of the Antarctic.
Klekociuk said scientists at Australia's Davis Antarctic base saw the first signs of cooling of the lower stratosphere, 15 to 25 km (nine to 15 miles) up, about six weeks earlier than usual.
In a visual sign the ozone hole would grow rapidly this year, scientists at Australia's Mawson base have reported the early appearance of stratospheric clouds, which create a spectacular light show by defracting sunlight around sunset.
Chemical reactions in these clouds convert normally inert man-made chlorofluorocarbons (CFCs) into ozone destroyers. CFCs have commonly been used in spray cans and air conditioners. But international accords have significantly curtailed their use.
Clouds do not usually form in the stratosphere due to its extreme dryness, but during some winters temperatures become low enough to allow their formation.
"In 2000 we didn't see the stratospheric clouds until the beginning of July. This year we saw them about the middle of May which is the earliest we have seen them," Klekociuk said.
The full extent of the 2003 ozone hole will not be known until the end of September, as August and September are the coldest months for the South Pole. Temperatures begin to warm by early October and the ozone layer will then start to recover.
Written by: Karen Jacobs, Planet Ark
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