The area covered by the Antarctic ozone hole reached more than 27 million square kilometers in September, the second-largest on record for this time of year after a similar event in 2000 briefly exceeded 28 million square kilometers. A comparable peak occurred in October 2015 at 27.9 million square kilometers.
Data from the Copernicus Atmosphere Monitoring Service shows the hole began growing earlier than average in August, driven by a very strong polar vortex and cold temperatures over the pole. It then grew rapidly from the start of September, reaching 27.4 million square kilometers.
Researchers Annika Seppälä, Dan Smale, and Hannah E. Kessenich from the University of Otago said they first predicted a severe ozone hole in May this year after observing changes in atmospheric circulation. The strong polar vortex, a wind pattern that forms each winter and encircles Antarctica, is a key driver of the hole's development.
Despite its large area, the 2026 ozone hole hasn't reached the depths of past large holes, meaning there is less total ozone missing overall. The scientists stress that the Montreal Protocol, the landmark global treaty designed to phase out ozone-depleting substances, is still working. Levels of these substances in the stratosphere have dropped by about a third since their peak around the year 2000.