Ozone layer faces record loss over Arctic due to chemicals, cold winter

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Ozone layer faces record loss over Arctic due to chemicals, cold winter

By Heilprin, The Associated Press | The Canadian Press – Tue, 5 Apr, 2011

5:47 AM EDT

GENEVA - The depletion of the ozone layer shielding Earth from damaging

ultraviolet rays has reached an unprecedented low over the Arctic this spring

because of harmful chemicals and a cold winter, the U.N. weather agency said

Tuesday.

The Earth's fragile ozone layer in the Arctic region has suffered a loss of

about 40 per cent from the start of winter until late March, exceeding the

previous seasonal loss of about 30 per cent, the World Meteorological

Organization said.

The Geneva-based agency blamed the loss on a buildup of ozone-eating chemicals

once widely used as coolants and fire retardants in a variety of appliances and

on very cold temperatures in the stratosphere, the second major layer of the

Earth's atmosphere, just above the troposphere.

Arctic ozone conditions vary more than the seasonal ozone " hole " that forms high

in the stratosphere near the South Pole each winter and spring, and the

temperatures are always warmer than over Antarctica.

Because of changing weather and temperatures some Arctic winters experience

almost no ozone loss while others with exceptionally cold stratospheric

conditions can occasionally lead to substantial ozone depletion, U.N. scientists

say.

This year the Arctic winter was warmer than average at ground level, but colder

in the stratosphere than normal Arctic winters. U.N. officials say the latest

losses — unprecedented, but not entirely unexpected — were detected in

observations from the ground and from balloons and satellites over the Arctic.

Atmospheric scientists who are concerned about global warming focus on the

Arctic because that is a region where the effects are expected to be felt first.

Ozone scientists have said that significant Arctic ozone depletion is possible

in the case of a cold and stable Arctic stratospheric winter. Ozone losses occur

over the polar regions when temperatures drop below -78 degrees Celsius (-108

Fahrenheit), when clouds form in the stratosphere.

Average temperatures in January range from about -40 to 0 C (-40 to 32 F), while

average temperatures in July range from about -10 to 10 C (14 to 50 F).

" The Arctic stratosphere continues to be vulnerable to ozone destruction caused

by ozone-depleting substances linked to human activities, " said WMO

secretary-general Michel Jarraud. " The degree of ozone loss experienced in any

particular winter depends on the meteorological conditions. "

The loss comes despite the U.N. ozone treaty, known as the 1987 Montreal

Protocol, which has resulted in cutbacks in ozone-damaging chemicals, such as

chlorofluorocarbons, halons and other, that were used in the making of

refrigerators, air conditioners, fire extinguishers and even hairspray.

The 196-nation ozone treaty encourages industries to use replacement chemicals

less damaging to ozone, the atmospheric layer that helps protect against the

sun's most harmful rays.

But because these compounds have long atmospheric lifetimes, it takes decades

for their concentrations to subside to pre-1980 levels as was agreed in the

Montreal Protocol.

U.N. officials project the ozone layer outside the polar regions will recover to

pre-1980 levels sometime between 2030 and 2040.