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Ozone Layer Day: Antarctic ozone hole expands to 25m square kilometres in 2026 – EnviroNews
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The 2026 Antarctic ozone hole has expanded rapidly in early September, reaching an estimated 25 million square kilometres on September 12, according to the Copernicus Atmosphere Monitoring Service (CAMS).
The development comes as the world marks the United Nations International Day for the Preservation of the Ozone Layer on September 16.
The Antarctic ozone hole is a region of severely depleted ozone over Antarctica that forms each spring due to chemical reactions involving chlorine and bromine, with recovery expected by the late 2060s.
CAMS said the ozone hole reached an area of 15 million square kilometres by the end of August – larger than the 14.2 million square-kilometre area of Antarctica itself.
The threshold was reached slightly earlier than the long-term average and followed a pattern similar to 2025, when the ozone hole reached the same area on August 30.
However, the ozone hole expanded sharply during the first half of September, reaching about 25 million square kilometres on September 12. This was approximately five million square kilometres above the average for that period, with forecasts indicating that it could expand further around the middle of September.
According to CAMS, the rapid expansion coincided with a sudden fall in minimum temperatures at about 20 kilometres above the South Pole, at the 50-hectopascal level.
The service explained that ozone depletion in the Southern Hemisphere stratosphere occurs when extremely cold temperatures facilitate the formation of polar stratospheric clouds. These clouds contribute to the activation of halogens, which chemically destroy ozone in the presence of sunlight during the austral spring, typically from August to November.
Despite the rapid increase in the size of the ozone hole, CAMS said other important indicators remained close to historical averages.
These include the minimum ozone column value within the defined ozone-hole area and the ozone mass deficit, a measure that combines changes in both the size and depth of the ozone hole.
“The Antarctic ozone hole’s development can vary considerably from year to year, depending on a range of atmospheric and chemical factors,” said Laurence Rouil, Director of CAMS.
“While we have seen its area increase rapidly in early September this year, other indicators remain close to historical averages,” she added.
Rouil stressed the importance of continued monitoring of the complex interaction between human-made disturbances and natural atmospheric factors.
“CAMS provides the high-quality data, forecasts and analyses needed to understand the state of the ozone layer and track its long-term recovery,” she said.
The ozone layer plays a critical role in protecting life on Earth by absorbing much of the Sun’s harmful ultraviolet radiation, exposure to which is a major risk factor for skin cancer.
For almost half a century, human emissions of ozone-depleting substances have caused significant thinning of the protective layer, with the effects particularly pronounced over Antarctica.
The Antarctic ozone hole develops annually because the region’s stable polar vortex and extremely cold stratospheric conditions create an environment favourable to ozone destruction.
Climate change also has implications for the ozone layer, as global warming tends to cool the stratosphere, potentially favouring the formation of polar stratospheric clouds involved in ozone depletion.
The Antarctic ozone hole has been monitored through ground-based and satellite observations since the late 1970s. Its largest recorded area was 29.6 million square kilometres on September 9, 2006.
CAMS noted, however, that recent years have generally seen smaller and shorter-lived ozone holes, a development consistent with the long-term recovery of the ozone layer following international action to phase out ozone-depleting substances.
The annual ozone hole is defined as the area where ozone concentrations fall below 220 Dobson Units (DU), a standard measurement of the amount of ozone in a vertical column of the atmosphere.
As the 2026 ozone hole continues to develop during the Antarctic spring, CAMS said continued observation will be essential for assessing its eventual size, depth and duration and for tracking the long-term recovery of the ozone layer.
