Saturday, June 21, 2008

Ozone threat to India

The closing down of Antarctic ozone hole in the second half of this century will spell trouble for the rest of the globe, a recent study led by scientists from Columbia University has hinted. Countries like India could be especially vulnerable.

According to the study, published in the June 13 issue of Science, the closing of the hole will intensify climate change near the equator.

The finding is in contrast to the observations made by the report of the Intergovermental Panel on Climate Change (IPCC). The Earth's ozone layer is in the lower stratosphere, which is just above the troposphere (from the planet's surface to a height of about 12 km). It absorbs harmful ultraviolet rays of the sun.

Widespread use of household and commercial aerosols, containing mainly chlorofluorocarbons (CFC), till the late 1990s, led to significant ozone depletion, putting the public health at risk. The production of CFC was phased out across the world in accordance with the Montreal Protocol, signed by 191 countries.

Studies in the past few years found that ozone depletion has largely halted and is expected to completely reverse. As a consequence, the climate in the southern hemisphere may change, affecting climate elsewhere.

"We were surprised to find that the closing of the ozone hole, expected to occur in the next 50 years or so, shows significant effects on the global climate," says Lorenzo M. Polvani, one of the two principle investigators involved in the study and a professor of applied physics and applied mathematics.

In the past few decades, the tropospheric winds in the southern hemisphere have been accelerating closer to the planet's pole as a result of increasing greenhouse gases and decreasing ozone with a broad range of effects on the Earth's climate.

The IPCC models predict that this effect will continue, albeit at a slower pace. In contrast, the latest study predicts that, as a consequence of ozone recovery - a factor largely ignored by the IPCC models - the tropospheric winds in the southern hemisphere may actually decelerate in the high latitudes and move toward the equator, potentially reversing the direction of climate change in that hemisphere. The effects will be felt the most by countries close to the equator. India, naturally, could be affected.

"Our results suggest that stratospheric ozone is important for the Southern Hemisphere climate change, and ought to be more carefully considered in the next set of IPCC model integrations," said Seok-Woo Son, lead-author of the study.

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