NASA: Ozone Hole Is Bigger Than Ever
Copyright 2000, Associated Press
September 9, 2000
Geneva-The hole in the ozone layer is now three times larger than the United States,its biggest size ever, scientists at NASA said Friday. UN weather experts said the hole over the Antarctic is growing earlier in the year than usual.Measurements of ozone depletion vary from year to year, making it difficult for scientists to determine the long-term environmental impact of changes in the ozone layer. Still, this year's hole-large and early-caught atmospheric experts off-guard.
"The fact that it's real big right now is kind of a surprise," said Dr.
Paul A. Newman of NASA's Goddard Space Flight Center in Greenbelt, Md.
The center detected an ozone hole of about 11 million square miles last Sunday. That was the biggest ever, beating the previous record of 10.5 million square miles on Sept. 19, 1998, it said.
Though ozone levels decrease each year starting in July, such a large drop was "unprecedented" this early in the season, the U.S. World Meteorological Observation said Friday.
Experts stressed that atmospheric variations from year to year combine with man-made gases to determine the hole's size.
Depletion of the ozone layer over Antarctica and the Arctic is being monitored because ozone protects Earth from harmful ultraviolet radiation. Too much UV radiation can cause skin cancer and destroy tiny plants at the beginning of the food chain.
Antarctic ozone depletion starts in July, when sunlight triggers chemical reactions in cold air trapped over the South Pole during the Antarctic winter.
It intensifies during August and September before tailing off in October as temperatures rise, reducing the ability of gases to destroy ozone.
Human-made chlorine compounds used in refrigerants, aerosol sprays, solvents, foam-blowing agents and bromine compounds used in firefighting halogens cause most ozone depletion.
Experts agree that the man-made chemicals are leveling off thanks to the Montreal Protocol, which commits countries to eliminating production and use of ozone-depleting substances. But it could be 20 years before ozone levels recover noticeably.
"There's going to be ups and downs on the long-term trend but the feeling is that we've probably bottomed out," said Russ Schnell, deputy director of the National Oceanic and Atmospheric Administration's climate change laboratory in Boulder, Colo.