Ozone Hole Over Antarctica Swells to 25 Million Sq Km in Early September

Measurements from the Copernicus Atmosphere Monitoring Service (CAMS) reveal a sudden and marked expansion of the ozone hole over Antarctica during the first half of September.

By 12 September, the hole had reached an area of 25 million square kilometres — approximately 5 million square kilometres above the long-term average for that period. In August, its growth followed a “normal” trajectory, reaching roughly 15 million square kilometres before accelerating unexpectedly at the start of September.

What triggered the rapid expansion?

Scientists attribute the abrupt enlargement to a sharp drop in stratospheric temperatures. Cold conditions enable the formation of polar stratospheric clouds — which, under sunlight, facilitate the chemical destruction of ozone by halogens, a group of highly reactive chemical elements including chlorine, fluorine, and iodine.

“The evolution of the Antarctic ozone hole can vary significantly from year to year, depending on a range of atmospheric and chemical factors,” said Laurence Rouil, Director of the Copernicus Atmosphere Monitoring Service. “While we observed its area increase rapidly in early September this year, other indicators remain close to historical averages.”

Rouil added: “These findings highlight the importance of monitoring the complex interplay between human-induced disturbances and natural factors.”

The role of the ozone layer

The ozone layer shields life on Earth by absorbing much of the sun’s ultraviolet radiation — a primary cause of skin cancers. For nearly five decades, human emissions have thinned the ozone layer, with the most pronounced thinning occurring over Antarctica, where the hole reopens each Southern Hemisphere spring — from September through November.

Context: August 2026 sets global heat records

This development follows shortly after CAMS confirmed that August 2026 was the hottest month globally on record, with a mean temperature of 16.96°C — surpassing the previous record of 16.95°C set in July 2023. Last month also registered the highest-ever average sea surface temperature, a clear indicator of strengthening El Niño conditions.