Thursday, June 12, 2008

Ozone Recovery Could Increase Warming


The recovery of Earth's protective ozone layer, expected to heal gradually over the next half-century or so, may be good news for your skin, but it could also put the brakes on a fast-moving wind current, further exacerbating global warming, a new study suggests.

The ozone layer protects Earth's inhabitants from harmful ultraviolet rays, which can cause skin cancer in humans as well as mutations in other organisms. This layer sits in the lower portion of the stratosphere, the layer of the atmosphere above the troposphere, where Earth's weather occurs (and we live). Ozone absorbs the sun's UV light here before it can reach the planet's surface.

The gaping hole in the ozone layer was discovered in 1985, eventually leading to the signing of the Montreal Protocol in 1987, which moved to ban the substances, such as chlorofluorcarbons (CFCs), which destroy stratospheric ozone. (The hole isn't a total absence of ozone, but a severe reduction in the concentration of ozone that occurs seasonally.)

The new study, detailed in the June 13 issue of the journal Science, compares current climate models used by the International Panel on Climate Change to predict the potential long-term consequences of global warming to another set of models that better account for chemical reactions in the stratosphere.

Study leader S-W. Son, of Columbia University in New York, and an international team of scientists found that the IPCC models fail to adequately model ozone recovery and its possible consequences. The other set of models they used showed that the healing of the ozone layer will warm the stratosphere, disrupting an important westerly wind jet closer to Earth's surface.

This jet would slow near the South Pole, which could affect surface temperatures, the extent of sea ice, storm tracks, the location of arid regions and wind-driven ocean circulation in the Southern Hemisphere, the authors of the study said.

Another recent study , detailed in the April 26 issue of the journal Geophysical Research Letters, also found that the recovery of the Antarctic ozone hole would warm up the atmosphere, subjecting the southernmost continent to the full effects of the warming pattern already affecting the rest of the world.

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