Ozone hole at smallest size in decades

Ozone hole at smallest size in decades

Warm Antarctic temperatures help preserve UV-protecting layer

Web edition: October 26, 2012

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SHRINKING OZONE HOLE

On September 22 (right), the hole in the ozone layer (blue and purple) above Antarctica reached its smallest maximum size in two decades, covering 21.2 million square kilometers. The largest ozone hole on record occurred on September 9, 2000 (left), measuring 29.9 million square kilometers.

Credit: GSFC/NASA

There?s good news from Antarctica this fall: The seasonal hole in the ozone layer above the continent reached its smallest maximum extent and second smallest average in 20 years thanks to warm air temperatures.

Each September and October the ozone layer, which shields Earth from ultraviolet radiation from the sun, thins over the South Pole. On September 22, the ozone hole grew to its biggest seasonal size: 21.2 million square kilometers, an area slightly smaller than North America. That?s the smallest the ozone hole has been at its annual maximum since 1990. Satellite and ground-based measurements collected by NASA and the National Oceanic and Atmospheric Administration put the average size of the 2012 ozone hole at 17.7 million square kilometers, the smallest average since 2002.

Reactions with chlorine from human-made chlorofluorocarbon gas are largely responsible for destroying the ozone layer. Frigid temperatures help promote this destruction. But natural weather fluctuations led to warmer Antarctic temperatures this year, which limited the damage, NASA and NOAA scientists say.

Suggested Reading

Ozone Hole Watch website: [Go to]

A. Witze. Ozone hole on the mend. Science News. Vol. 179, June 4, 2011, p. 15. [Go to]

J. Raloff. Record ozone thinning looms in Arctic. Science News. Vol. 179, April 9, 2011, p. 12. [Go to]

S. Perkins. Ozone hole might not recover until the year 2065. Science News. Vol. 168, December 24, 2005, p. 418. [Go to]

Source: http://www.sciencenews.org/view/generic/id/346068/title/Ozone_hole_at_smallest_size_in_decades

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