Signs that the ozone hole is recovering

Nature : The hole in the ozone layer over Antarctica is starting to heal, say researchers in Australia, who have published their findings in Geophysical Research Letters. Thanks to the Montreal Protocol of 1989, which banned the use of chlorofluorocarbons and other ozone-destroying chemicals, levels of anthropogenic ozone depleters detected in the region’s stratosphere have been falling since around the turn of the millennium, writes James Mitchell Crow for Nature. Before Murry Salby, an environmental scientist at Macquarie University in Sydney, Australia, and his colleagues could investigate manmade ozone depletion, however, they first had to account for the naturally occurring annual fluctuation in ozone levels. The researchers found that average springtime levels are linked to changes in a particular pattern of stratospheric weather known as dynamical forcing. Once they figured that out, they were able to detect the gradual recovery of the ozone levels, which had declined precipitously until the late 1990s before beginning a slow rebound. A complicating factor in predicting future ozone levels will be the influence of climate change, said David Karoly, a climate scientist at the University of Melbourne, Australia.