April 28, 2008 -- Fixing the ozone hole may affect climate change -- and vice versa -- according to two new studies.
In the first case, Judith Perlwitz of the University of Colorado at Boulder and colleagues reported that as the ozone hole heals over the next century, it may cause warming over the Antarctic continent via changing wind patterns.
Her team's findings suggest that a complete regeneration of the ozone hole could result in the lower atmosphere warming over the Antarctic by as much as 5.4 degrees Fahrenheit.
The climate models used by the Intergovernmental Panel on Climate Change do not represent the stratosphere properly, said Ted Shepherd of the University of Toronto, who was not involved with the study. The effects of the ozone hole -- which occurs in the stratosphere -- on climate are not properly simulated, he said.
Perlwitz's model, however, simulates how stratospheric ozone chemistry interacts with the climate below.
When it forms in the early spring, the ozone hole cools the stratosphere, because there is less ozone to trap the sun's energy. This cooling leads to stronger westerlies, swirling winds that circle the pole, holding the cold air over the continent.
As the ozone hole closes, Perlwitz found, the stratospheric cooling decreases, weakening the westerly winds and allowing warmer air from lower latitudes into the weather systems over the continent.
The findings are published in the current issue of Geophysical Research Letters.
It is too early to tell what effect these changes have at the surface, but Shepherd points out that shifting winds are likely to alter the ocean currents that circle the Antarctic.
"Whatever changes have happened in the past" as the ozone hole grew, Shepherd said, "you might worry that they might change direction" as the hole is repaired.
In other findings published last Thursday in Science, Simone Tilmes of the National Center for Atmospheric Research in Boulder, Colo., and colleagues analyzed proposals to combat climate change by seeding the atmosphere with sulfate aerosols designed to reflect sunlight back into space.
These proposals aim to mimic the global cooling seen after the eruption of Mt. Pinatubo in 1991 spewed such aerosols into the stratosphere.
But if those proposals are ever put to test, the intended cooling could come with an unintended consequence to the ozone hole.
Tilmes' findings show that -- as happened with the Mt. Pinatubo eruption -- these aerosols could activate the chlorine in the stratosphere to destroy ozone.
The team estimated that under the right weather conditions, injecting enough aerosols to compensate for a doubling of atmospheric CO2 could deplete as much ozone as is present in the Arctic lower stratosphere, and could delay healing of the Antarctic ozone hole by 30 to 70 years.
Both researchers said not to make the ozone hole a climate villain.
"We have to remind ourselves that the ozone hole is very bad for life on Earth," Perlwitz emphasized. "It is good news that the ozone hole is going to heal. What is important is that we stop injecting so many greenhouse gases into the atmosphere. That is the main evil."
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Discovery News blog: Earth Impacts