October 19, 2007
NASA: Ozone Hole Returns to Average Size
WASHINGTON -- The Antarctic ozone hole is back to an average size, shrinking about 16 percent from last year's record high, NASA said Friday. But it's still the size of North America.
The ozone hole in mid-September reached a maximum size of 9.7 million square miles, down from its peak of 11.5 million square miles last year, said NASA atmospheric scientist Paul Newman.Human produced gases, containing chlorine and bromine, damage the Earth's protective ozone layer, forming a hole over the South Pole and into the Southern hemisphere. Because the ozone layer protects life on Earth by blocking ultraviolet rays, countries across the world 20 years ago agreed to ban many compounds such as spray-can propellants.
The ozone hole was first discovered in 1985, is not natural, and at the current rate should be closed up by 2070, Newman said. Nearly 80 percent of the ozone-depleting chemicals in the atmosphere are man-made.
But those compounds stay in the atmosphere 40 to 100 years and the total amount of chlorine compounds in the air is only down 3.1 percent since 2001, Newman said. For the past 15 years or so, the ozone hole has been about the same size, going up slightly and down slightly, mostly based on the weather, he said. It appears from July to October.
Warmer weather and more storms this year are the reason the hole is slightly smaller, Newman said.
"There's no way we could say we're seeing real improvement, but it's smaller because of the weather situation," Newman said.
On the Net:
NASA's ozone hole watch: http://ozonewatch.gsfc.nasa.gov/