Saturday, May 14, 2011

Ozone hole on the mend

This blog sometimes seems to provide an unending scroll of downers, so I’m pleased to post an optimistic turn of events, from Alexandra Witze in Science News: Scientists may have spotted Antarctica’s ozone hole on the road to recovery, at least a decade sooner than they thought healing would be noticeable. In 1989, an international agreement called the Montreal Protocol began phasing out chemicals that have gnawed away at Earth’s protective ozone layer. Most researchers thought it would take until at least 2023 to detect the hole’s slow recovery, but researchers in Australia now claim to have seen ozone ticking upward since the late 1990s.

“The key is to account for large year-to-year fluctuations that have obscured a gradual increase in the long-term evolution of ozone,” says atmospheric scientist Murry Salby of Macquarie University in Sydney. His team published its findings online May 6 in Geophysical Research Letters.

First spotted in 1985, the Antarctic ozone hole was quickly linked to chemicals called chlorofluorocarbons, emitted mainly in the Northern Hemisphere but concentrated over the South Pole by atmospheric circulation patterns. Chlorine atoms from these CFCs react with ozone molecules, seasonally destroying the layer that shields Earth from cancer-causing and crop-damaging ultraviolet radiation.

Scientists had predicted that ozone loss would bottom out and start recovering by now. They just didn’t think they would be able detect that change yet, since ozone levels vary dramatically from year to year because of complex atmospheric processes, sometimes by almost as much as the magnitude of the ozone hole itself…

A rendering of the ozone hole from NASA

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