Ozone depletion over Arctic at record level: WMO

Yahoo News 5 Apr 11;

GENEVA (AFP) – Depletion of the ozone layer over the Arctic has reached record levels, and Nordic countries will have to watch for higher than normal ultraviolet radiation in coming weeks, the UN weather agency said Tuesday.

The Arctic ozone layer suffered a loss of about 40 percent from the beginning of winter to late March, up from the previous record of about 30 percent over the entire winter, according to the World Meteorological Organisation.

"Depletion of the ozone layer -- the shield that protects life on Earth from harmful levels of ultraviolet rays -- has reached an unprecedented level over the Arctic this spring because of the continuing presence of ozone-depleting substances in the atmosphere and a very cold winter in the stratosphere," the WMO said in a statement.

With the ozone deficient region shifting away in late March from the pole to cover Greenland and Scandinavia, these Nordic regions would have to watch for higher than normal ultraviolet radiation in coming weeks.

"As the solar elevation at noon increases over the next weeks, regions affected by the ozone depletion will experience higher than normal UV radiation," said the WMO.

"The public is recommended to stay informed through national UV forecasts," it said.

The stratosphere is the second major layer of the atmosphere, and about 90 percent of the ozone in the atmosphere is found here.

Stratospheric ozone provides a natural protective filter against harmful ultra-violet rays from the sun, which can cause sunburn, cataracts and skin cancer and damage vegetation.

Its depletion is caused by extreme cold temperatures at high altitude and a particular type of pollution, from chemicals often used in refrigeration, some plastic foams, or aerosol sprays, which have accumulated in the atmosphere.

Most of the chemicals, chloroflurocarbons (CFCs), are being phased out under the 1987 Montreal Protocol, but they linger in the atmosphere for many years.

Thanks to the accord, however, the ozone layer outside the polar regions is projected to recover to its pre-1980 levels at around 2030 to 2040.

Over the Antarctic, the ozone layer is expected to recover at around 2045 to 2060 while over the Arctic, this should happen one or two decades earlier.

"The degree of ozone loss experienced in any particular winter depends on the meteorological conditions," noted Michel Jarraud, WMO secretary-general.

"The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities," he said.

"The 2011 ozone loss shows that we have to remain vigilant and keep a close eye on the situation in the Arctic in the coming years," added the UN weather chief.

Ozone layer faces record 40 pct loss over Arctic
John Heilprin Associated Press Yahoo News 5 Apr 11;

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.

Online:

WMO: http://www.wmo.int/pages/index_en.html

UN ozone: http://ozone.unep.org/