By Tom Miles
GENEVA, Oct 29 (Reuters) - The U.N.'s weather and climate
agency said on Thursday there was no cause for alarm about a
record-size hole this month in the ozone layer, that shields
life on earth from the sun, as it should shrink again.
The ozone hole that appears over Antarctica fluctuates in
size, normally reaching its widest in the polar spring as
extreme cold temperatures in the stratosphere and the return of
sunlight unleash chlorine radicals that destroy ozone.
Last year, the World Meteorological Organization (WMO) said
it detected the first sign of ozone recovery, largely thanks to
a 1987 ban on gases that cause ozone depletion, but said it
could be a decade before the hole begins shrinking. urn:newsml:reuters.com:*:nL5N0RB5G5
This year, a colder than usual stratosphere widened the hole
to a peak of 28.2 million square km (10.9 million square miles)
on Oct. 2, bigger than Canada and Russia put together.
It was a record for a hole recorded on Oct. 2 of any year,
and the hole has remained at daily record levels on every day
since then, the WMO said, citing data from NASA. Over the 30
days around the peak, the hole averaged 26.9 million square km,
making it the third largest, after 2000 and 2006.
"This shows us that the ozone hole problem is still with us
and we need to remain vigilant. But there is no reason for undue
alarm," WMO Atmospheric and Environment Research Division senior
scientist Geir Braathen said in a statement.
"Overall, however, this does not reverse the projected
long-term recovery in the coming decades," the statement said.
Ozone depleting chemicals, including the chlorofluorocarbons
(CFCs) once widely used in refrigerators and spray cans, were
banned under the 1987 Montreal Protocol. The U.N. Environment
Programme has said the treaty will prevent 2 million cases of
skin cancer annually by 2030.
"The Montreal Protocol is in place and is working well,"
Braathen said.
"But we may continue to see large Antarctic ozone holes
until about 2025 because of weather conditions in the
stratosphere and because ozone depleting chemicals linger in the
atmosphere for several decades after they have been phased out."
(Editing by Louise Ireland)