Ozone hole 'healing' but warming to increase

The hole in the ozone layer which has caused environmentalists concern for years is said to repairing itself, but experts warn that in doing so it could inadvertently be increasing warming.

According to a study untaken at the University of Leeds the repair of the ozone layer hole could potentially raise temperatures in the southern hemisphere.

Researchers claim the Antarctic ozone hole, which was once regarded as one of the biggest environmental threats to the planet, is instead helping to shield the region from carbon-induced warming.

Scientists say high-speed winds in the area beneath the hole have led to the formation of brighter summertime clouds, which reflect more of the sun's powerful rays.

"These clouds have acted like a mirror to the sun's rays, reflecting the sun's heat away from the surface to the extent that warming from rising carbon emissions has effectively been cancelled out in this region during the summertime," said co-author Professor Ken Carslaw from the University of Leeds.

"If, as seems likely, these winds die down, rising CO2 emissions could then cause the warming of the southern hemisphere to accelerate, which would have an impact on future climate predictions."

Those behind the research say the key to the newly-discovered feedback is aerosol. Greenhouse gases absorb infrared radiation from the Earth and release it back into the atmosphere as heat, causing the planet to warm-up over time. Aerosol works against this by reflecting heat from the sun back into space, cooling the planet as it does so.

The researchers said that beneath the Antarctic ozone hole, high-speed winds whip up large amounts of sea spray, which contains millions of tiny salt particles. This spray then forms droplets and eventually clouds, and the increased spray over the last two decades has made these clouds brighter and more reflective. As the ozone layer recovers it is believed that this feedback mechanism could decline in effectiveness, or even be reversed, leading to accelerated warming in the southern hemisphere.

"Our research highlights the value of today's state-of- the-art models and long-term datasets that enable such unexpected and complex climate feedbacks to be detected and accounted for in our future predictions," added Professor Carslaw.