Ozone hole stretches to record size, exposes Chilean city
October 6, 2000
WELLINGTON, New Zealand (AP) -- The hole in the ozone layer over
Antarctica stretched over a Chilean city when it ballooned to a
record size last month, the first time it has reached a
population center, scientists said Thursday.
Previously, the hole had only opened over Antarctica and the
surrounding ocean.
Citing data from the U.S. space agency NASA, atmospheric research
scientist Stephen Wood said the hole covered 11.4 million square
miles -- an area more than three times the size of the United
States -- on Sept. 9 and 10.
For those two days, the hole extended over Punta Arenas, a
southern Chile city of about 120,000 people, exposing residents
to very high levels of ultraviolet radiation. Too much UV
radiation can cause skin cancer and destroy tiny plants at the
beginning of the food chain.
Wood is a researcher with New Zealand's respected National
Institute of Water and Atmospheric Research.
Dr. Dean Peterson, science strategy manager of the Antarctica New
Zealand research group, said Wood's findings showed a city being
exposed to the ozone hole for the first time.
"The longer it gets, the greater the chances of populated areas
being hit by low ozone levels," said Peterson, who was not
involved in the study.
Peterson said smaller spots of low ozone could affect Argentina
and even the tip of South Africa, Australia or New Zealand.
"The hole won't grow to that size," he said. "But as it breaks
apart, fingers of low ozone, or filaments as we call them, will
go over major land mass areas. Those filaments will be over the
land mass for a few weeks."
Last month, scientists expressed surprise when NASA data from
Sept. 3 showed the hole at just under 11 million square miles --
the biggest it had ever been. It continued to grow in the days
afterward, according to the data cited by Wood.
Record-low temperatures in the stratosphere are believed to have
helped the expansion of the ozone hole during the southern
hemisphere's spring season.
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 as temperatures rise in late November or early
December.
Depletion of the ozone layer over Antarctica and the Arctic is
being monitored because ozone protects Earth from harmful
ultraviolet radiation.
Human-made chlorine compounds used in refrigerants, aerosol
sprays, solvents, foam-blowing agents and bromine compounds used
in firefighting halogens cause most ozone depletion. The
temperature over Antarctica also significantly affects the size
of each year's hole. Starting in October, warmer temperatures
reduce the ability of chlorine and other gases to destroy ozone.
Experts agree that the man-made chemicals are leveling off thanks
to the 1989 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.
"Although CFC levels will begin to reduce over the next 10 years,
variations in the weather pattern will continue," Peterson said.
Article by the Associated Press
SOURCE: CNN
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