Posted on 23-8-2003
2003
Ozone Hole May Be Record Size, Australia Says
By Michael Perry, Reuters, 22 August 2003
SYDNEY (Reuters) - 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 10.9
million square 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
lightshow by defracting sunlight around sunset. Chemical reactions
in these clouds convert normally inert man-made chlorofluorocarbons
(CFCs) into ozone destroyers. CFCs are commonly used as propellants
in spray cans. The 1997 Kyoto treaty set in place a global process
to reduce greenhouse gases which deplete the ozone layer, but
the world's biggest polluter the United States has yet to sign.
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.
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