Antarctic ozone hole expanded above average in September
Its area was estimated at 25 million km2 on 12 September, while other measures of ozone depletion remained near historical averages.
The Antarctic ozone hole grew rapidly during early September 2026, reaching an estimated 25 million km2 on 12 September, according to the Copernicus Atmosphere Monitoring Service (CAMS). That was around 5 million km2 larger than the average for that point in the season.
The hole had expanded to 15 million km2 by the end of August, passing that threshold slightly ahead of the usual timing. Its development was similar to 2025, when it reached that size on 30 August. CAMS said growth since the second half of August had otherwise followed a typical pace.
Despite the larger area, CAMS reported near-average readings for two other indicators: the minimum ozone column value inside the hole and the ozone mass deficit. CAMS Director Laurence Rouil said atmospheric conditions and chemical factors can produce substantial differences between years, making continued monitoring important.
The rapid expansion coincided with a sharp fall in minimum temperatures in the stratosphere above the South Pole. Cold conditions allow polar stratospheric clouds to form, helping activate chemical processes that remove ozone when sunlight returns during the austral spring. The ozone layer absorbs much of the harmful ultraviolet radiation reaching Earth.
