ESA Finds Improvement In Antarctic Ozone Hole; Largely Attributable To Weather, Temperature - AFP

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The ozone hole over Antarctica shrank by 30 percent this year compared with the record loss recorded in 2006, the European Space Agency (ESA) said on Wednesday. Measurements made by the agency's Envisat satellite found a peak loss in the ozone layer of 27.7 million tonnes, compared to 40 million tonnes last year, it said in a press release.

Ozone, a molecule of oxygen, forms a thin layer in the stratosphere, filtering out dangerous ultraviolet sunlight that damages vegetation and can cause skin cancer and cataracts. The protectively layer has been badly damaged by man-made chlorine-based chemicals. The hole -- in essence, a thinning of the layer -- goes through a cycle each year as the chemical reaction that drives depletion peaks during the deep chill of the southern hemisphere winter, from late August to October.

In 2006, the ozone hole at its biggest measured 28 million square kilometers (10.81 million square miles); in 2007, it was 24.7 million sq. kms. (9.53 million sq. miles), or roughly the size of North America.

Ronald van der A, a senior project scientist at Royal Dutch Meteorological Institute (KNMI), said this year's improvement could not be seen as a confirmation that the ozone layer was in recovery. "This year's ozone hole was less centred on the South Pole as in other years, which allowed it to mix with warmer air, reducing the growth of the hole, because ozone is depleted at temperatures less than -78 degrees Celsius (- 108 degrees Fahrenheit)," he said.

EDIT

http://www.terradaily.com/2007/071003143458.sn6idvuo.html