Thursday, 26 October, 2000, 01:13 GMT 02:13 UK
Arctic ozone damage 'likely by 2020'
BAS scientists pioneered Antarctic ozone research
By Alex Kirby, BBC News Online
environment correspondent and presenter of Costing the Earth
One of the three British scientists who discovered the Antarctic
ozone hole says similar damage is likely soon in the Arctic.
The scientist, Jonathan Shanklin, says the Earth's ozone layer is
cooling, which makes its recovery more difficult.
The cooling is the result partly of ozone loss itself, and also
of a little-noticed effect of global warming.
And although ozone-depleting gases are no longer increasing in
the atmosphere, the damage is being maintained by a feedback
mechanism.
The ozone layer protects all living creatures against harmful
ultra-violet radiation from the Sun, which in humans can damage
the eyes and the immune system and also cause skin cancer.
Cooling atmosphere
Mr Shanklin, who with Joseph Farman and Brian Gardiner of the
British Antarctic Survey discovered the Antarctic ozone hole in
1985, was speaking to BBC Radio Four's environment programme
Costing the Earth.
He said: "The atmosphere is changing, and one of the key changes
is that the ozone layer is getting colder.
"It's getting colder because of the greenhouse gases that are
being liberated by all the emissions we have at the surface.
"And when it gets colder, particularly during the winter, we can
get clouds actually forming in the ozone layer, and these clouds
are the key factor.
"Chemistry can take place on them that activates the chlorine and
makes it very much easier for it to destroy the ozone.
"We think that within the next 20 years we're likely to see an
ozone hole perhaps as big as the present one over Antarctica, but
over the North Pole."
This year's Antarctic hole, the largest recorded, reached as far
as the Falkland Islands and the tip of South America, where
people were warned to protect themselves against the Sun.
But while most of the area covered by the hole is uninhabited, a
similar Arctic hole would affect parts of densely-populated
Europe, Asia and North America.
Recovery delayed
The international ozone protection agreement, the Montreal
Protocol, has succeeded in arresting the build-up of
chlorofluorocarbons and other gases.
But although that should have been enough to allow the ozone to
start gradually repairing itself, recovery still appears
unlikely, because of a feedback.
The World Meteorological Organisation says: "Chemicals that
result in ozone destruction are no longer increasing in the
stratosphere, as the international controls on ozone-depleting
chemicals continue to work.
"However, the continued general decrease of ozone in the lower
stratosphere and the global increase in greenhouse gases are now
believed to result in lower temperatures in the lower
stratosphere.
"These decreases in temperature could expand the period of
intense ozone loss during the ozone hole period."
Dr Michael Proffitt, WMO's senior scientific officer, says the
ozone hole has intensified since 1995 - and something else has
happened too.
"During this period, the area with temperatures low enough for
polar stratospheric clouds that initiate rapid ozone destruction
to form during October is double that found during any earlier
five-year period," Dr Proffitt said.
Warming and cooling
Put simply, the stratosphere where the ozone has thinned is able
to trap less incoming UV radiation, which cools it and makes
further thinning more likely.
And while the greenhouse gases are warming the Earth's surface,
climate models suggest they are having a corresponding cooling
effect in the stratosphere.
In a final confounding of ozone depletion and global warming,
some scientists believe that ozone depletion is helping to offset
warming lower down, masking the real impact of the greenhouse
gases.
SOURCE: BBC News
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