By IANS,
Washington : Global warming will set back the recovery of the ozone layer of the earth’s atmosphere, warns a NASA study.
Previous studies have shown that while the build up of greenhouse gases makes it warmer in the troposphere, up to 10 km high from sea level, these gases actually cool the upper stratosphere, between 30 to 50 km high.
This cooling slows the chemical reactions that deplete ozone in the upper stratosphere and allows natural ozone production in that region to outpace destruction of the ozone layer by chlorofluorocarbons (CFCs).
But the accumulation of greenhouse gases also changes the circulation of stratospheric air masses from the tropics to the poles, NASA scientists note.
In the earth’s middle latitudes, that means ozone is likely to “over-recover”, growing to concentrations higher than they were before the mass production of CFCs. In the tropics, stratospheric circulation changes could prevent the ozone layer from fully recovering.
“Most studies of ozone and global change have focussed on cooling in the upper stratosphere,” said Feng Li, atmospheric scientist at the University of Maryland, Baltimore, and co-author of the study. “But we find circulation is just as important. It’s not one process or the other, but both.”
The findings are based on a detailed computer model that includes atmospheric chemical effects, wind changes and solar radiation changes, said a Maryland university release.
These findings were published in the March edition of Atmospheric Chemistry and Physics.