Decades of chemical pollution have damaged the ozone layer of the upper atmosphere that shields Earth from the harmful effects of the sun's ultraviolet rays, each summer eating a hole over the South Pole that expands to nearly the size of Antarctica. But since 1996, when an international treaty banned the culprit chemical refrigerants and propellants (known as CFCs, or chlorofluorocarbons), the size of the seasonal tear has been shrinking—and scientists predict it may stop forming by the end of this century.
That is not just good news for the ozone hole, it is also good news for the climate. Atmospheric scientists note in a new study published in Science that sewing up the rift in the ozone (a type of oxygen) layer may help heal another environmental woe: climate change.
The reason: closing the gash may affect the flow of winds known as the westerlies around Antarctica, which impact everything from the extent of sea ice to the location of deserts in the Southern Hemisphere. According to scientific studies and mathematical models developed for the United Nations Intergovernmental Panel on Climate Change (IPCC)—which last year determined that the changing climate is largely a man-made danger—global warming has shifted these winds toward the poles, altering weather patterns throughout the Southern Hemisphere. The new research shows that mending the ozone may reverse warming in Antarctica and, potentially, the globe.
"The winds drive everything," says study author Lorenzo Polvani, an atmospheric scientist at Columbia University, "locations of storms, dry zones and deserts, the ice and the ocean circulation as well as the carbon uptake of the oceans." For decades, these winds have been speeding up near Antarctica; repairing the ozone would weaken the winds, he says, and shift them back toward the equator, affecting weather in the entire Southern Hemisphere, including Antarctica as well as Australia, parts of Africa and South America.
This also means Earth's southernmost continent might experience warming in future as the winds continue to shift and allow relatively warmer air to cover it, potentially speeding the melting of ice shelves. In addition, if there were no hole, the replenished ozone would trap even more heat as greenhouse gas concentrations also rise, according to Polvani.
Atmospheric scientist Judith Perlwitz of the University of Colorado at Boulder and her colleagues reached a similar conclusion, published recently in the journal Geophysical Research Letters. But she notes that none of the models on which scientists base these predictions tell the whole story, because they have yet to include all possible variables in their calculations. For instance, she says, no one has factored in the role that the ocean—critical to the regulation of Earth's temperature—would play if the ozone hole is closed.
Perlwitz says that computer simulations including ocean impacts are now being run, and could help scientists better predict the potential consequences of global warming and the changing ozone—and what must be done to limit the damage.
*Erratum (6/16/08): We regret the misunderstanding created by the original headline and wording of this article, which stated that mending the ozone layer could speed climate change.
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