Warmer air temperatures high above the Antarctic led to the second smallest seasonal ozone hole in 20 years, according to NOAA and NASA satellite measurements. This year, the average size of the ozone hole was 6.9 million square miles (17.9 million square kilometers). The ozone layer helps shield life on Earth from potentially harmful ultraviolet (UV) radiation that can cause skin cancer and damage plants.
The Antarctic ozone hole forms in September and October, and this year, the hole reached its maximum size for the season on Sept. 22, stretching to 8.2 million square miles (21.2 million square kilometers), roughly the area of the United States, Canada and Mexico combined. In comparison, the largest ozone hole recorded to date was in 2000 at 11.5 million square miles (29.9 million square kilometers).
The Antarctic ozone hole began making a yearly appearance in the early 1980s, caused by chlorine released by manmade chemicals called chlorofluorocarbons or CFCs. The chlorine can rapidly break apart ozone molecules in certain conditions, and the temperature of the lower stratosphere plays an important role.
“It happened to be a bit warmer this year high in the atmosphere above Antarctica, and that meant we didn’t see quite as much ozone depletion as we saw last year, when it was colder,” said Jim Butler with NOAA’s Earth System Research Laboratory in Boulder, Colo.
http://www.noaanews.noaa.gov/stories2012/20121024_antarcticozonehole.html
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