Have you ever heard of the southern jet stream? It’s a powerful wind that shapes weather patterns and ocean currents in the southern hemisphere, particularly in the summer. Up until about 2000, it had been shifting from its usual course and moving southwards towards the Antarctic at a rate of one degree of latitude each decade, affecting storm tracks and rainfall over South America, East Africa, and Australia.
Affected by holes in the ozone layer
Previous research has shown this was primarily driven by the depletion of the ozone layer by manmade chemical compounds such as chlorofluorocarbons and hydrochlorofluorocarbons, found in fridges, aerosols and other industrial processes. These chemicals, which were used in vast quantities until they started to be phased out under the United Nations 1987 Montreal protocol, thinned the ozone layer, causing a widening “hole” high above the south pole that affected wind patterns.
Back on track
But according to a paper, the Montreal protocol made a huge impact. Not only has it allowed the ozone repair itself, but its also helping to return the southern jet stream to a normal state after decades of human-caused disruption. The new paper, published in the journal Nature, shows that the Montreal protocol has paused the southward movement of the jet stream since the turn of the century and may even be starting to reverse it as the ozone hole begins to close.
Last September, satellite images revealed the ozone hole annual peak had shrunk to 16.4m sq km, the smallest extent since 1982. It’s a success story in international cooperation and should motivate us further as we fight to spare the planet from the climate crisis.
Source study: Nature – A pause in Southern Hemisphere circulation trends due to the Montreal Protocol