WMO reports record stratospheric ozone loss in the Arctic

[News_Editor]

WMO reports record stratospheric ozone loss in the Arctic

2011-04-05 17:27:45 GMT+7 (ICT)

GENEVA (BNO NEWS) --­ 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 World Meteorological Organization (WMO) said on Tuesday. The stratosphere is the second major layer of the Earth's atmosphere, just above the troposphere.

The record loss is despite an international agreement which the WMO said has been 'very successful' in cutting production and consumption of ozone destroying chemicals. But because of the long atmospheric lifetimes of these compounds, it will take several decades before their concentrations are back down to pre-1980 levels, the target agreed in the Montreal Protocol on Substances that Deplete the Ozone Layer.

The Organization said on Monday that the observations from the ground and from balloons over the Arctic region as well as from satellites showed that the Arctic region has suffered an ozone column loss of about 40 percent from the beginning of the winter to late March. The highest ozone previously recorded was about 30 percent over the entire winter.

In Antarctica, the so-called ozone hole is an annually recurring winter and spring phenomenon due to the existence of extremely low temperatures in the stratosphere. In the Arctic, however, the the meteorological conditions vary much more from year to year and the temperatures are always warmer than over Antarctica. Hence, some Arctic winters experience almost no ozone loss, whereas cold stratospheric temperatures in the Arctic lasting beyond the polar night can occasionally lead to substantial ozone loss.

And even though this Arctic winter was warmer than average at ground level, it was far colder in the stratosphere than for a normal Arctic winter, the WMO said.

But while the degree of Arctic ozone destruction in 2011 is unprecedented, WMO said it was not unexpected. Ozone scientists had earlier said that significant Arctic ozone loss is to be expected in the case of a cold and stable Arctic stratospheric winter.

Stratospheric ozone depletion occurs over the polar regions when temperatures drop blow -78 Celsius (-108.4 Fahrenheit), and such low temperatures clouds form in the stratosphere. Chemical reactions that convert innocuous reservoir gases into active ozone depleting gases take place on the clouds particles and the result is a rapid destruction of ozone if sunlight is present.

Ozone depleting substances such as chlorofluorocarbons (CFCs) and halons, which were once present in refrigerators, spray cans and fire extinguishers, have been phased out under the Montreal Protocol. As a result, the ozone layer outside the polar regions is projected to recover to its pre-1980 levels between 2030 and 2040, according to WMO and the United Nations Environment Programme (UNEP).

In contrast, however, the springtime ozone layer over the Antarctic is expected to recover between 2045 and 2060, while the Arctic will probably recover 10 to 20 years earlier. But without the Montreal Protocol, WMO believes this year's ozone destruction would have been far worse.

"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 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."

Jarraud said the WMO's Global Atmosphere Watch Network has many stations in the Arctic that help the Organization obtain an early warning in the case of low ozone and intense ultraviolet (UV) radiation.

If the ozone depleted areas move away from the pole and towards lower latitudes, one can expect increased UV radiation as compared to the normal for the season. And as the solar elevation at noon increases over the weeks, regions affected by the ozone depletion will experience higher than normal UV radiation. WMO advises the public to stay informed through national UV forecasts.

"It should be pointed out, however, that the UV radiation will not increase to the same intensity as one suffers in the tropical regions of the globe," WMO said. "The sun is still relatively low in the sky, and this limits the amount of UV radiation that passes through the atmosphere."

UV-B rays have been linked to skin cancer, cataracts and damage to the human immune system. Some crops and forms of marine life can also suffer adverse effects.

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