Ozone hole 8% larger this year, meteorologists say

The ozone hole over Antarctica, a doorway for harmful solar radiation, is bigger than last year, a worrying sign to scientists studying global warming, the World Meteorological Organization said.

The area of atmosphere without ozone has grown to 27 million square kilometers (10.4 million square miles), 8 percent larger than the maximum reached in 2007, the group said today in an e- mailed statement. The hole usually reaches its maximum in late September or early October before receding in an annual cycle.

The ozone layer, which shields the Earth from biologically harmful sun rays, has been measured since the 1950s. The ozone 5 to 6 miles above ground has gained importance among scientists studying how a warmer climate worldwide might alter the layer.

The depletion this year is probably a temporary reversal in a long-term improvement of the ozone layer, said David Parsons, the meteorological organization's chief for world weather research.

"You can have strong annual variations, due to changes in weather, colder temperatures in the stratosphere and increased water vapor" that can undercut the ozone layer, Parsons said in an interview from Geneva.

"It's important to keep your eye on the long-term trend, which is that the ozone hole is moving toward recovery," Parsons said. Scientists credit the improvement largely to the 1987 international agreement to cut use of chemicals known as CFCs and HCFCs such as from spray cans that enlarged the ozone hole.

The interplay between warmer surface temperatures on Earth and the ozone high in the stratosphere is a growing area of research.

"The observed changes in the stratosphere could delay the expected recovery of the ozone layer," the statement said. "Scientists are increasingly aware of the possible links between ozone depletion and climate change."

Increased emissions of carbon dioxide from power plants and vehicles, while warming the atmosphere's lowest level, or troposphere, actually help cool the stratosphere. There, lower temperatures speed up the chemical reactions that destroy ozone.

In turn, a cooler stratosphere will affect weather patterns and climate. "The effects go both ways," Parsons said.

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