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
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
"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.
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