The Stratosphere, the Earth’s second lowest atmospheric layer, which lies between10 and 50 kilometers (6 and 31 miles) above the surface, contains 90 percent of all atmospheric ozone. Ozone filters out harmful UV rays from the sun. Ozone declined steadily from 1979 through1997, correlating well with a peak production of ozone-destroying gases such as chlorofluorocarbons or CFC’s. CFC’s were phased out after the 1987 international Montreal Protocol was enacted.
To measure ozone at different layers in the atmosphere Dr. Yang’s team used data from balloons, along with independent ground-based observing networks, as well as monthly averaged satellite data which came from five independent NASA and NOAA instruments. The measurements were compared to computer predictions of ozone recovery that factored in variations in human produced ozone destroying chemicals.
Results of the study confirm that the Stratosphere is no longer being depleted of ozone and that levels could be restored to those of 1980, by sometime in the middle of the century.