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By John Heilprin, Associated Press Tue Apr 5, 7:01 pm ET
GENEVA The protective ozone layer in the Arctic that keeps out the sun's most
damaging rays ultraviolet radiation has thinned about 40 percent this
winter, a record drop, the U.N. weather agency said Tuesday.
The Arctic's damaged stratospheric ozone layer isn't the best known "ozone
hole" that would be Antarctica's, which forms when sunlight returns in spring
there each year. But the Arctic's situation is due to similar causes:
ozone-munching compounds in air pollutants that are chemically triggered by a
combination of extremely cold temperatures and sunlight.
The losses this winter in the Arctic's fragile ozone atmospheric layer strongly
exceeded the previous seasonal loss of about 30 percent, the U.N.'s World
Meteorological Organization in Geneva said.
It blamed the combination of very cold temperatures in the stratosphere, the
second major layer of the Earth's atmosphere, just above the troposphere, and
ozone-eating CFCs from aerosol sprays and refrigeration.
"This is pretty sudden and unusual," said Bryan Johnson, an atmospheric chemist
who works in the U.S. National Oceanic and Atmospheric Administration's Earth
System Laboratory in Boulder, Colorado.
Atmospheric scientists concerned about global warming focus on the Arctic
because that is a region where the effects are expected to be felt first.
"The Arctic stratosphere continues to be vulnerable to ozone destruction caused
by ozone-depleting substances linked to human activities," the U.N. weather
agency's secretary-general Michel Jarraud said.
Although the thinner ozone means more radiation can hit Earth's surface, the
ozone levels in the Arctic remain higher than in other regions such as in the
equatorial regions, said the National Oceanic and Atmospheric Administration,
whose recent Arctic findings mirror those of the U.N. agency.
Ozone losses occur over the polar regions when temperatures drop below -78
degrees Celsius (-108 Fahrenheit) and iridescent ice clouds form. Sunlight on
icy surfaces triggers the ozone-eating reactions in chlorine and bromine that
comes from air pollutants such as chlorofluorocarbons, or CFCs, once widely
used as refrigerants and flame retardants in household appliances.
"As sunlight returns, it all comes together to trigger significant thinning of
the ozone," Johnson explained.
"Mostly the concern, for the Arctic ozone depletion, is for people that live in
northern regions, more towards Iceland, northern Norway, the northern coast of
Russia," he added, saying they should be more careful outside, wearing
sunscreen and sunglasses.
As of late March, the U.N. said, the thinning ozone was shifting away from the
pole and was covering Greenland and Scandinavia.
For the planet, Johnson said, there's the concern that "if this were to happen
every year even though the ozone naturally regenerates itself you might see
a trending downward of the atmospheric ozone layer."
After scientists raised warnings in the early 1970s later earning a Nobel
Prize virtually all the world's nations agreed to the 1987 treaty called the
Montreal Protocol to cut back on CFCs used in air conditioning, aerosol sprays,
foam packaging and other products.
But the compounds have long atmospheric lifetimes, so it takes decades for
their concentrations to subside to the pre-1980 levels agreed to in the
Montreal Protocol. The ozone layer outside the polar regions isn't expected to
recover to pre-1980 levels until sometime between 2030 and 2040.
The ozone treaty also encourages industries to use replacement chemicals less
damaging to ozone.
Some scientists say if that treaty hadn't been adopted, two-thirds of the
world's protective ozone layer would be gone about a half-century from now and
the CFCs, which also are long-lived potent greenhouse gases, would have pushed
the world's temperature up an extra few degrees.
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 in the Arctic than over Antarctica.
Because of the changing weather and temperatures that some Arctic winters
experience, there have been times where there is almost no ozone loss, and
others when the exceptionally cold stratospheric conditions has led 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. Average Arctic temperatures in January range
from about -40 to 0 C (-40 to 32 F) and in July from about -10 to 10 C (14 to
50 F).
U.N. officials say the latest losses unprecedented, but not entirely
unexpected were detected in satellite observations and weather balloons that
show at what altitudes the ozone loss is occurring.
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Online:
WMO: http://www.wmo.int/pages/index_en.html
UN ozone: http://ozone.unep.org/