- 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.
-
-
-
- Copyright © 2003 Reuters Limited. All rights reserved.
Republication or redistribution of Reuters content is expressly prohibited
without the prior written consent of Reuters. Reuters shall not be liable
for any errors or delays in the content, or for any actions taken in reliance
thereon.
|
