Scientists at MIT and elsewhere have identified the "first fingerprints¹ of healing" of the Antarctic ozone² layer, published today in the journal Science. The team found that the September ozone hole has shrunk by more than 4 million square kilometers -- about half the area of the contiguous United States -- since 2000, when ozone depletion³ was at its peak. The team also showed for the first time that this recovery has slowed somewhat at times, due to the effects of volcanic⁴ eruptions⁵ from year to year. Overall, however, the ozone hole appears to be on a healing path.

 

The authors used "fingerprints" of the ozone changes with season and altitude to attribute the ozone's recovery to the continuing decline of atmospheric⁶ chlorine originating from chlorofluorocarbons (CFCs). These chemical compounds were once emitted by dry cleaning processes, old refrigerators, and aerosols⁷ such as hairspray. In 1987, virtually every country in the world signed on to the Montreal Protocol⁸ in a concerted effort to ban the use of CFCs and repair the ozone hole.

 

"We can now be confident that the things we've done have put the planet on a path to heal," says lead author Susan Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT. "Which is pretty good for us, isn't it? Aren't we amazing humans, that we did something that created a situation that we decided⁹ collectively, as a world, 'Let's get rid of these molecules'? We got rid of them, and now we're seeing the planet respond."

 

Solomon's co-authors include Diane Ivy¹⁰, research scientist in the Department of Earth, Atmospheric and Planetary Sciences, along with researchers at the National Center for Atmospheric Research in Boulder¹¹, Colorado, and the University of Leeds in the U.K.

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