Smithsonian Magazine · People & society

Antarctic Ozone Hole Reaches Largest Size in 25 Years

The Antarctic ozone hole in September reached 10.6 million square miles, its second-largest extent on record for that month, according to the Copernicus Atmosphere Monitoring Service. This year's hole began expanding earlier than usual.

The ozone layer protects Earth from harmful UV radiation. The ozone hole, a depletion over Antarctica, is primarily caused by persistent chlorofluorocarbons (CFCs) phased out by the Montreal Protocol. The hole's size fluctuates annually, opening within the polar vortex during the Southern Hemisphere's spring, where cold temperatures and polar stratospheric clouds facilitate ozone-depleting chemical reactions.

This year's larger hole is attributed to a stronger and colder polar vortex, creating conditions for significant growth. The hole is expected to shrink by late January. Wildfire smoke particles can also contribute to ozone depletion.

Despite the size, experts state this year's hole is not a cause for alarm and does not indicate the Montreal Protocol is failing. Recovery is assessed by the hole's depth, which is less severe this year. Long-term trends show the ozone hole is slowly recovering as expected.

The larger ozone hole influences Southern Hemisphere weather patterns, such as increasing rainfall in southeastern Australia. Researchers are investigating the impact of climate change on polar vortex strength and the persistence of ozone holes, which may necessitate adjustments to recovery timelines.

Further research is needed to understand the drivers of recent dynamical variability and the increasing likelihood of longer-lived ozone holes.

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