http://reuters.com/newsArticle.jhtml?type=scienceNews&storyID=3320163
2003
Ozone Hole May Be Record Size, Australia Says
Fri August 22, 2003 02:57 AM ET
By Michael Perry
[
See
photograph from original article... ]
CAPTION:
"A polar stratospheric cloud appears above Australia's
Mawson Antarctic base in this undated handout picture.
Australian scientists warn the ozone hole over the ice
continent could grow to a record size in 2003 due
to colder stratospheric temperatures, which result
in the formation of clouds, that convert inert man-made
gases into ozone destroying chemicals. Photo by Reuters
(Handout)"
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.
