NASA, NOAA Data Indicate Ozone
Layer is Recovering
August 30, 2006
A new study using NASA and National Oceanic and Atmospheric Administration
(NOAA) data finds consistent evidence that Earth's ozone layer is on the mend.
A team led by Dr. Eun-Su Yang of the Georgia Institute of Technology, Atlanta,
analyzed 25 years of independent ozone observations at different altitudes in
Earth's stratosphere, which lies between 10 and 50 kilometers (six and 31 miles)
above the surface. The observations were gathered from balloons, ground-based
instruments and NASA/NOAA satellites.
The stratosphere is Earth's second lowest atmospheric layer. It contains
approximately 90 percent of all atmospheric ozone. The researchers concluded the
Earth's protective ozone layer outside of the polar regions stopped thinning
around 1997. Ozone in these areas declined steadily from 1979 to 1997.
NASA/NOAA satellite data showing the rise in stratospheric chlorine and
corresponding decline in ozone layer thickness from 1979 to 1997. As
stratospheric chlorine declined in response to enactment of the Montreal
Protocol, the first stage of ozone recovery began.
The abundance of human-produced ozone-destroying gases such as
chlorofluorocarbons peaked at about the same time (1993 in the lowest layer of
the atmosphere, 1997 in the stratosphere). Such substances were phased out after
the 1987 international Montreal Protocol was enacted.
To measure ozone at different altitudes in the stratosphere, the team combined
data from balloons and independent ground-based observing networks with monthly
averaged satellite data. The satellite data came from five independent NASA and
Measurements were compared with computer predictions of ozone recovery that
considered actual measured variations in human-produced ozone-destroying
chemicals. The calculations took into account other factors that can affect
ozone levels, such as sunspot cycle behavior, seasonal changes and stratospheric
"These results confirm the Montreal Protocol and its amendments have succeeded
in stopping the loss of ozone in the stratosphere," Yang said. "At the current
recovery rate, the atmospheric modeling community's best estimates predict the
global ozone layer could be restored to 1980 levels — the time that scientists
first noticed the harmful effects human activities were having on atmospheric
ozone — sometime in the middle of this century."
The researchers concluded approximately one half the observed ozone change was
in the region of the stratosphere above 18 kilometers (11 miles) and the rest in
the lowermost stratosphere from 10 to 18 kilometers (6 to 11 miles). The
researchers attribute the ozone improvement above 18 kilometers almost entirely
to the Montreal Protocol.
"Scientists expected the Montreal Protocol to be working in the middle and upper
stratosphere and it is," said co-author Dr. Mike Newchurch of the University of
Alabama in Huntsville. "The real surprise of our research was the degree of
ozone recovery we found at lower altitudes, below the middle stratosphere.
There, ozone is improving faster than we expected, and appears to be due to
changes in atmospheric wind patterns, the causes of which are not yet well
understood. Until the cause of the recent ozone increase in the lowermost
stratosphere is better understood, making high-accuracy predictions of how the
entire ozone layer will behave in the future will remain an elusive goal.
Continued careful observation and modeling are required to understand how the
ozone recovery process will evolve."
"Our study is unique because it measures changes in the ozone layer at all
heights in the atmosphere, then compares the data with models as well as
observations from other instruments that measure variations in the total amount
of ozone in the atmosphere," said Dr. Ross Salawitch, a senior research
scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Results are published in the Journal of Geophysical Research - Atmospheres. For
information about NASA and agency programs, visit:
Other media contacts: Chris Rink, NASA's Langley Research Center, Hampton, Va.,
757-864-6786; Jane Sanders, Georgia Institute of Technology, 404-894-2214; Nina
Stickles, Hampton University, Va., 757-727-5457; Anatta, NOAA, Boulder, Colo.,
303-497-6288; Phil Gentry, University of Alabama, Huntsville, 256-824-6420; and
Harvey Leifert, American Geophysical Union, Washington, 202-777-7507.
JPL is managed for NASA by the California Institute of Technology in Pasadena.