NASA: Climate Change and Atmospheric Circulation Will Make for Uneven Ozone Recovery

Ozone Hole image

NASA

4/9/2009

Earth's ozone layer should eventually recover from the unintended destruction brought on by the use of chlorofluorocarbons (CFCs) and similar ozone-depleting chemicals in the 20th century.

But new research by NASA scientists suggests the ozone layer of the future is unlikely to look much like the past because greenhouse gases are changing the dynamics of the atmosphere.

 Previous studies have shown that while the buildup of greenhouse gases makes it warmer in troposphere – the level of atmosphere from Earth’s surface up to 10 kilometers (6 miles) altitude – it actually cools the upper stratosphere – between 30 to 50 kilometers high (18 to 31 miles). '

This cooling slows the chemical reactions that deplete ozone in the upper stratosphere and allows natural ozone production in that region to outpace destruction by 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 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 focused on cooling in the upper stratosphere," said Feng Li, an atmospheric scientist at the Goddard Earth Sciences and Technology Center at the University of Maryland Baltimore County, Baltimore, Md. and lead author of the study. "But we find circulation is just as important. It's not one process or the other, but both."

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