Ozone Hole Recovery may Affect Global Climate Change

Recovery of the ozone hole may exert a huge effect on climate change in the Southern Hemisphere, and therefore, the global climate, a new study using computer models has found.

The study, led by Columbia University researchers in the US, has determined that the recovery of the ozone hole is projected to occur sometime in the second half of the 21st century.

The Earth's ozone layer is located in the lower stratosphere, which lies just above the troposphere (which begins at the planet's surface and reaches up to about 12 km), catching harmful ultraviolet rays from the sun.

Until late in the last century, widespread usage of household and commercial aerosols containing chlorofluorocarbons (CFC), unstable compounds which are carried into the stratosphere, lead to significant and rapid ozone depletion.

But, due to the Montreal Protocol, signed by 191 countries, CFC production worldwide was phased out in 1996.

bservations in the last few years indicate that ozone depletion has largely halted and is expected to fully reverse. As a consequence, the new study finds, the Southern Hemisphere climate change may also reverse.

"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.

The chemistry-climate models used for the 2006 Ozone Assessment, predict that the Antarctic ozone hole will achieve full recovery in the second half of this century, and that this may have profound impacts on the surface winds.

It will also have impact on other aspects of the Earth's climate, including surface temperatures, locations of storm tracks, extent of dry zones, amount of sea ice, and ocean circulation.

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.

This wind change has had 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, predictions made by the chemistry-climate models indicate that, as a consequence of ozone recovery, a factor largely ignored by 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.

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

Source-ANI
RAS/L