Annual growth spurt hit early this year, NASA says

Saturday, September 9, 2000

Geir Moulson
Associated Press

GENEVA -- The gap in the ozone layer is nearly three times as large as the United States -- its biggest size ever, scientists at NASA said yesterday. U.N. 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, the size and early onset of this year's hole caught atmospheric experts off-guard.

``The fact that it's real big right now is kind of a surprise,'' said Paul A. Newman of the National Aeronautics and Space Administration's Goddard Space Flight Center in Greenbelt, Md.

The center detected a gap of about 11 million square miles on Sunday. That was the biggest ever, beating the previous record of 10.5 million square miles on Sept. 19, 1998, it said.

In Geneva, the U.N. World Meteorological Observation said stations in the Antarctic reported decreases in ozone of between 10 percent and 50 percent compared with the period between 1964 and 1976, before the ozone hole was observed. Although ozone levels decrease each year starting in July, such a large drop was unprecedented this early in the season, the U.N. group said yesterday.

``It is remarkable to find these low values so early in September, perhaps one or two weeks earlier than in any previous year,'' the agency said.

Experts stressed that atmospheric variations from year to year combine with man-made gases to determine the hole's size. They said they can't be certain what the measurements mean for the rest of this year and beyond.

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 bottom 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.

Circular winds, known as vortexes, trap air, giving chemicals the chance to react with the ozone.

``The polar vortex is bigger this year -- bigger than 1998,'' Newman said. ``The containment vessel is larger, and so the size is larger.''

Its size raises concerns that ``We're perhaps beginning to see some evidence of climate change in the stratosphere,'' although no firm evidence is available, he said.

``Maybe we have to be a little more serious about looking at this problem of the interaction of global warming and stratosphere cooling and ozone loss.''

The strength of the vortex means the ozone hole might persist a few days longer than usual, breaking up in December, Newman said.

Human-made chlorine compounds used in refrigerants, aerosol sprays, solvents, foam-blowing agents and bromine compounds used in firefighting halogens cause most ozone depletion.

Newman said he expects that ozone levels inside the Antarctic area covered by the hole will continue to drop over the coming week, but he said the area of the hole has stabilized over the past week and is unlikely to grow significantly.

``The true story won't come out for another three or four weeks,'' said Russ Schnell, deputy director of the National Oceanic and Atmospheric Administration's climate change laboratory in Boulder, Colo.

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,'' Schnell said.