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Scientists credit
weird weather, not pollution control Margaret Munro National Post, with files from Reuters
While the news sounds encouraging, scientists say the phenomenon
has little to do with pollution control and much to do with weird weather in
the upper stratosphere. ''This is the smallest ozone hole since 1988, but that's still a
lot of ozone loss,'' said Paul Newman, an ozone researcher at NASA's Goddard
Space Flight Center. The ozone layer protects Earth from the sun's ultraviolet
radiation, which can cause cancer and burn crops. Scientists caution that
depletion of the ozone layer is still a concern. The 2002 Antarctic ozone hole covers about 16 million square kilometres, well below the 24 million square kilometres seen for the last six years at this time of
year. The most significant ozone loss is usually seen over the
Antarctic in late September, so climatologists have been watching this year's
strange developments with keen interest. ''It began to form up like a pair of dumbbells,'' said Tom
McElroy, an ozone specialist at Environment Canada who has been observing the
action over the last few weeks on the climate networks that monitor ozone and
post the data on the Internet. Seeing the hole develop into two pieces -- instead of forming a
large vortex or hole over the southern continent -- was a new wrinkle on a
phenomenon scientists first observed in the 1970s. Climatologists say the small size of this year's ozone hole was
caused by unexpectedly large weather patterns in the stratosphere, the layer
of the atmosphere 10 to 48 kilometres above Earth's
surface where the ozone layer is found. Normally, stratospheric weather in the extreme southern
hemisphere is placid, allowing for a large ozone hole
to open up, Mr. Newman said. This year, unusually large weather patterns
pumped ozone into the south polar region and warmed it up. ''The warm air actually shuts down ozone loss,'' Mr. Newman
said. The strange weather also caused the ozone hole to split into two
lobes, he said. Dr. McElroy says the strange stratospheric weather and ozone
hole may not be such a good sign. ''It may be another indication of climate
change associated with global warming,'' he said in an interview yesterday. Then again, he cautions against reading too much into the
development. One year, he said, does not make a climate trend. Ozone loss is triggered by chlorine and bromine, ozone-eating
chemicals contained in chlorofluorocarbons and halons,
human-made chemicals once common in hair spray, refrigerators and air
conditioners. The ''hole'' (it is not actually a hole through the layer, but
an area of significantly low ozone concentration) in the ozone layer over the
Antarctic was discovered by Dr. Joe Farman of the
British Antarctic Survey and was dramatic news when details were published. Chlorofluorocarbons and halons were
banned under the Montreal Protocol in 1987 and scientists report that the levels of the compounds in the atmosphere is dropping. But
the impact of the pollutants on the atmosphere is so long-lasting that the The coldest temperatures over the South Pole typically occur in
August and September, when thin clouds form and chemical reactions help
chlorine and bromine gases to destroy ozone. In early October temperatures
begin to warm, and ozone-rich air from outside the
hole mixes with the ozone-depleted air, resulting is the disappearance of the
Antarctic ozone hole by late November. © Copyright
2002 National Post |