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NASA OBSERVATIONS CONFIRM EXPECTED OZONE LAYER
RECOVERY
NASA satellite observations have provided the first evidence the
rate of ozone depletion in the Earth's upper atmosphere is
decreasing. This may indicate the first stage of ozone layer
recovery.
From an analysis of ozone observations from NASA's first and
second Stratospheric Aerosol and Gas Experiment (SAGE) and the
Halogen Occultation Experiment (HALOE) satellite instruments,
scientists have found less ozone depletion in the upper
stratosphere (22-28 miles altitude) after 1997. The American
Geophysical Union Journal of Geophysical Research has accepted a
paper for publication on these results.
This decrease in the rate of ozone depletion is consistent with
the decline in the atmospheric abundance of man-made chorine and
bromine-containing chemicals that have been documented by
satellite, balloon, aircraft and ground based measurements.
Concerns about ozone depletion in the upper atmosphere or
stratosphere led to ratification of the Montreal Protocol on
Substances that Deplete the Ozone Layer by the international
community in 1987. The protocol restricts the manufacture and use
of human-made, ozone-depleting compounds, such as
chlorofluorocarbons and halons.
"Ozone is still decreasing but just not as fast," said Mike
Newchurch, associate professor at the University of Alabama,
Huntsville, Ala., and lead scientist on the study. "We are still
decades away from total ozone recovery. There are a number of
remaining uncertainties such as the effect of climate change on
ozone recovery. Hence, there is a need to continue this precise
long-term ozone data record," he said.
"This finding would have been impossible had either SAGE II or
HALOE not lasted so long past their normal mission lifetime," said
Joe Zawodny, scientist on the SAGE II satellite instrument science
team at NASA's Langley Research Center, Hampton, Va.
SAGE II is approaching the 19th anniversary of its launch, and
HALOE has been returning data for 11 years. Scientists also used
international ground networks to confirm these
data from satellite results.
SAGE I was launched on the Applications Explorer Mission-B
spacecraft in 1979; the Earth Radiation Budget Satellite carried
SAGE II into orbit in 1984. The Space Shuttle Discovery carried
HALOE into space on the Upper Atmosphere Research Satellite in
1991.
NASA's Earth Science Enterprise funded this research in an
effort to better understand and protect our home planet. The ozone
layer protects the Earth's surface from the sun's harmful
ultraviolet rays. Ultraviolet radiation can contribute to skin
cancer and cataracts in humans and harm other animals and plants.
Ozone depletion in the stratosphere also causes the ozone hole that
occurs each spring over Antarctica.
For information about NASA on the Internet, visit:
www.nasa.gov
For information about NASA's Earth Science Enterprise on the
Internet, visit:
www.earth.nasa.gov
For information about this research on the Internet, visit:
www-sage2.larc.nasa.gov
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