The Ozone Hole

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Elvia Thompson
Headquarters, Washington       September 30, 2002
(Phone: 202/358-1696)
Robert J. Gutro/Cynthia M. O'Carroll
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-4044 / 614-5563)
Carmeyia Gillis 
National Oceanic and Atmospheric Administration/NOAA Climate 
Prediction Center
(Phone: 301/763-8000, ext. 7163)
RELEASE: 02-185
Scientists from NASA and the Commerce Department's National Oceanic and
Atmospheric Administration (NOAA) have confirmed the ozone hole over the
Antarctic this September is not only much smaller than it was in 2000 and
2001, but has split into two separate "holes." 
The researchers stressed the smaller hole is due to this year's peculiar
stratospheric weather patterns and that a single year's unusual pattern
does not make a long-term trend. Moreover, they said, the data are not
conclusive that the ozone layer is recovering. 
Paul Newman, a lead ozone researcher at NASA's Goddard Space Flight
Center, Greenbelt, Md., said this year, warmer-than-normal temperatures
around the edge of the polar vortex that forms annually in the
stratosphere over Antarctica are responsible for the smaller ozone loss. 
Estimates for the last two weeks of the size of the Antarctic Ozone Hole
(the region with total column ozone below 220 Dobson Units), from the NASA
Earth Probe Total Ozone Mapping Spectrometer (EPTOMS) and the NOAA-16
Solar Backscatter Ultraviolet instrument (SBUV/2), are around 15 million
square kilometers (6 million square miles). These values are well below
the more-than 24 million sq. km. (9 million sq. mi.) seen the last six
years for the same time of year. 
The stratosphere is a portion of the atmosphere about 6-to-30 miles above
the Earth's surface where the ozone layer is found. The ozone layer
prevents the sun's harmful ultraviolet radiation from reaching the Earth's
surface. Ultraviolet radiation is a primary cause of skin cancer. Without
protective upper-level ozone, there would be no life on Earth. 
"The Southern Hemisphere's stratosphere was unusually disturbed this
year," said Craig Long, meteorologist at NOAA's Climate Prediction Center
(CPC). The unusual weather patterns were so strong, the ozone hole split
into two pieces during late September. NOAA's CPC has been monitoring and
studying the ozone since the early 1970s. "This is the first time we've
seen the polar vortex split in September," said Long. 
At South Pole Station, balloon-borne ozone-measuring instruments launched
by NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL) reveal the
vertical structure of the developing ozone hole. Bryan Johnson, a
scientist with CMDL, said the main ozone depletion region, from 7-to-14
miles above the Earth, has large ozone losses, similar to the last few
years. At more than 15 miles above the Earth, surface measurements show
higher-than-normal ozone concentrations and higher temperatures. 
The combination of these layers indicate total ozone levels in a column of
atmosphere will be higher than observed during the last few years, Johnson
said. However, some layers may still show complete ozone destruction by
early October, when ozone depletion is greatest. 
In 2001, the Antarctic ozone hole was larger than the combined area of the
United States, Canada and Mexico. The last time the ozone hole was this
small was in 1988, and that was also due to warm atmospheric temperatures. 
"While chlorine and bromine chemicals cause the ozone hole, temperature is
also a key factor in ozone loss," Newman said.  The Montreal Protocol and
its amendments banned chlorine- containing chlorofluorocarbons (CFCs) and
bromine-containing halons in 1995, because of their destructive effect on
the ozone layer. However, CFCs and halons are extremely long- lived and
still linger at high concentrations in the atmosphere. 
The coldest temperatures over the South Pole typically occur in August and
September. Thin clouds form in these cold conditions, and chemical
reactions on the cloud particles help chlorine and bromine gases to
rapidly destroy ozone. By early October, temperatures usually begin to
warm, and thereafter the ozone layer starts to recover. 
NOAA and NASA continuously observe Antarctic ozone with a combination of
ground, balloon, and satellite-based instruments. 
For more information and images see: