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.