Scientists Detect Beginning of Ozone Hole Healing
According to an article in Nature, researchers have spotted signs of recovery in the ozone hole above Antarctica.
These first signs of human-caused shrinkage come 22 years after the Montreal Protocol, an international agreement that banned the use of ozone-depleting chloroflurocarbons. Levels of CFCs, as they’re known, have been falling since about 2000, though researchers have been unable do detect a corresponding decrease in the size of the ozone hole because the hole naturally fluctuates each spring.
In fact, researchers had believed that they would be unable to detect the effects of the Montreal Protocol for decades. It was only because an Australian scientist, Murry Salby, figured out that the natural fluctuations were tied to a weather pattern known as dynamic forcing. Once scientists knew how to predict the natural fluctuations, they could then remove them from the real-world data they collected, revealing the changes wrought by the ban on CFCs. Using this method of analysis yields data that mirror the drop in chlorine detected after the CFC ban, lending it even more credence.
Dynamic forcing occurs, according to the Nature article, when more cold air is trapped above the pole in the winter, more ice crystals remain in the atmosphere, which hasten the destruction of ozone by providing a surface on which the reaction between ozone and chlorine can take place during the spring.
"I think this is the first convincing observationally-derived evidence of the ozone rebound," Adrian McDonald, an atmospheric scientist at the University of Canterbury in Christchurch, New Zealand, told Nature. "It's the first where the statistical significance is high enough, and you can see the pattern well enough, that you feel comfortable in believing it."