It has been more than 30 years since the world banned the chemicals that were depleting Earth’s protective ozone layer and simultaneously triggering some troubling changes in atmospheric circulation in the Southern Hemisphere. Now, new research published this week in Nature finds that those changes have paused and might even be reversing because of the Montreal Protocol—an international treaty that successfully phased out use of ozone-depleting chemicals.
The ozone hole, discovered in 1985, has been forming every spring in the atmosphere high over Antarctica. Ozone depletion cools the air, strengthening the winds of the polar vortex and affecting winds all the way down to the lowest layer of Earth’s atmosphere. Ultimately, ozone depletion has shifted the mid-latitude jet stream and the dry regions at the edge of the tropics toward the South Pole. Previous studies have linked these circulation trends to weather changes in the Southern Hemisphere, especially rainfall over South America, East Africa, and Australia, and to changes in ocean currents and salinity.
The Montreal Protocol of 1987 phased out production of ozone-destroying substances such as chlorofluorocarbons (CFCs). Beginning around 2000, concentrations of those chemicals in the stratosphere started to decline and the ozone hole began to recover. This study has shown that around the year 2000, the circulation of the Southern Hemisphere also stopped expanding pole wards—a pause or slight reversal of the earlier trends.
With ozone recovering and CO2 levels continuing to climb, the future is less certain, including for those Southern Hemisphere regions whose weather is affected by the jet stream and those at the edge of the dry regions. However, a 2018 report from the United Nations says that the infamous hole in the ozone layer could be totally healed by the 2060s—and in some areas of the world, it could be as soon as 2030.
