Healing ozone layer may contribute to global warming

Wednesday, January 27, 2010

The ozone hole over Antarctica in September 2006, when it was at its largest recorded size.
Image: NASA.

Scientists from the UK's University of Leeds and the University of Kuopio in Finland report that the hole in the Earth's ozone layer over Antarctica may have offset some of the effects of climate change, and that as it heals, warming could accelerate. Their paper is published today in the journal Geophysical Research Letters.

The group studied twenty years of records of global weather conditions and wind speeds. They say that beneath the ozone hole, wind speeds are increased, which whips up more sea spray. Salt from this is carried upwards and makes the clouds brighter, reflecting more of the Sun's radiation. This helps cool the Earth, counteracting the effects of global warming.

The ozone layer in the atmosphere protects life from the harmful effects of ultraviolet radiation, and the discovery of its rapid depletion in the 1980s caused widespread alarm. The Montreal Protocol adopted in 1987 forced countries to phase out chlorofluorocarbons (CFCs), the man-made chemicals thought to be largely responsible for the hole.

Professor Ken Carslaw, of the University of Leeds School of Earth and Environment, was one of the co-authors of the paper. He warned that as the ozone hole healed, warming in parts of the Southern Hemisphere could accelerate.

"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," he said

Describing the findings as "unexpected and complex climate feedback", Professor Carslaw emphasised that this research was not a reason to try and keep the hole open:

The ozone hole was potentially a major catastrophe for the planet that was only stopped by the Montreal Protocol, so we can't go back on that

—Professor Ken Carslaw

"You can't correct two wrongs in that way. The ozone hole was potentially a major catastrophe for the planet that was only stopped by the Montreal Protocol, so we can't go back on that."

He said instead that carbon emissions should be cut drastically.

The research was funded by the Natural Environment Research Council and the Academy of Finland Centre of Excellence Programme.

Judith Perlwitz, a resercher at the US National Oceanic and Atmospheric Administration, said that the group's data were sound but she disagreed with some of the paper's conclusions. Perlwitz claimed that rising temperatures due to global warming would increase wind speeds anyway, leading to the same effects as the ozone hole.

“The question is whether the wind is really going to slow down, and that I doubt,” she said.

According to a World Meteorological Organization report in 2006, it is likely to be at least fifty years before the ozone above Antarctica is back to its pre-1980 state.