Record low ozone levels found over the Arctic
THE PROTECTIVE OZONE LAYER over the Arctic that keeps out the sun’s most damaging rays – ultraviolet radiation – has thinned about 40 per cent over the Northern Hemispehere winter, a record drop, the UN weather agency announced this week.
The Arctic’s damaged stratospheric ozone layer isn’t the best known ‘ozone hole’. Antarctica’s ozone hole, which forms when sunlight returns in spring there each year, has long been reported. But the Arctic’s situation is due to similar causes: ozone-munching compounds in air pollutants that are chemically trigged by a combination of extremely cold temperatures and sunlight.
The losses this winter in the Arctic’s fragile ozone layer strongly exceeded the previous seasonal loss of about 30 per cent, the UN’s World Meteorological Organisation 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 Dr Bryan Johnson, an atmospheric chemist who works in the US National Oceanic and Atmospheric Administration’s Earth System Laboratory in Boulder, Colorado.
Canary in the coal mine: arctic first to feel the effects of climate change
Atmospheric scientists concerned about global waming focis on the Arctic becaus this region is expected to feel the first effects of climate chanfe. “The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities,” the UN weather agency’s secretary-general Michel Jarraud said.
Although the thinner ozone means more radiation can hit Earth’s surface, the ozone leabels in the Arctic remain higher than in other regions such as the equitorial regions, said the National Oceanic and Atmospheric Administration, whose recent Arctic findings mirror those of the UN agency.
Ozone losses occur over the polar regions when temperatures drop below -78ºC 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,” Bryan explained. “Mostly the concern, for the Arctic ozone depletion, is for people who 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 UN said, the thinning ozone was shifting away from the pole and was covering Greenland and Scandinavia.
For the planet, Bryan 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.”
World pact to lower CFC emissions
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 the ozone. Some scientists say if that treaty hadn’t been adopted, two-thirds of the world’s protective ozone layer would be gone in about half a century from now and the CFCs, which are also 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 hight 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, UN 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 -40ºC to 0ºC and in July from about -10ºC to 10ºC. 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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