From the BBC News, 16 October 2000:
ARCTIC OZONE DAMAGE 'LIKELY BY 2020'
This article can found in its entirety at:
http://news.bbc.co.uk/hi/english/sci/tech/newsid_990000/990391.stm
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.
The Antarctic is an ideal laboratory.
Dr. Shanklin 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."
Ozone loss at present affects mainly researchers.
"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.