A team of researchers used satellite data and climate modeling to understand how the recovery of the ozone layer has affected the Earth’s atmosphere. On September 16th, 1987, an international treaty was signed to reduce emissions from ozone depleting chemicals into the atmosphere. Called the Montreal Protocol, the agreement has led to the gradual recovery of the hole in the ozone layer over Antarctica.
The depletion of the ozone layer had resulted in noticeable changes in three trends in the Earth’s atmosphere. The band of strong winds known as the mid-latitude jet stream had been shifting poleward in the Southern Hemisphere. The Southern Annular Mode, the north-south movement of the wind belts that circles the southern Hemisphere, has also been moving southward due to the ozone hole over Antarctica. The ozone conditions have also widened the Hadley cell, which affects tropical storms and hurricanes.
Sharon Robinson, from the University of Wollongong’s (UOW) Centre for Sustainable Ecosystem Solutions who published research in 2019 on ‘Ozone depletion, ultraviolet radiation, climate change and prospects for a sustainable future’ in Nature Sustainability, explained how ozone depletion drives climate change:
“Ozone is a greenhouse gas, so the ozone hole has kept Antarctica cooler, pulling the westerly wind jet that circles the continent closer and tighter to Antarctica. This has increased the speed of the wind, making Antarctica cooler and drier, pulling other Southern Hemisphere weather zones further south.”
Since the enactment of the Montreal Protocol, the ozone layer has been slowly recovering. In 2019, NASA and NOAA scientists reported the ozone hole had reached its smallest observed size since 1982.
The research, published online on March 25, 2020 in Nature, uses remote sensing and climate simulations to see how the shrinking of the ozone hole has affected global wind patterns. Led by Antara Banerjee at the University of Colorado Boulder, the authors found that the three trends had either paused or started to reverse starting in 2000. Banerjee and the other researchers also determined that these trends were not attributable to natural variability in climate systems but were the direct result of changes in human activities.
Banerjee, A., Fyfe, J. C., Polvani, L. M., Waugh, D., & Chang, K.-L. (2020). A pause in Southern Hemisphere circulation trends due to the Montreal Protocol. Nature, 579(7800), 544–548. https://doi.org/10.1038/s41586-020-2120-4
International regulations have paused a jet-stream shift in the Southern Hemisphere. (2020, March 25). Nature. https://www.nature.com/articles/d41586-020-00787-x
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