NASA says 2026 Antarctic ozone hole reached 10.5 million square miles, decade high

NASA and NOAA said the 2026 Antarctic ozone hole peaked on Sept. 18 at 10.5 million square miles, or 27.1 million square kilometers, and averaged 9.6 million square miles from Sept. 7 to Oct. 13. The average made it the seventh-largest in 48 years of observations. The agencies said the seasonal peak reflects the usual Antarctic spring chemistry, when sunlight and cold stratospheric clouds drive ozone loss.

The agencies attributed the expansion mainly to an unusually strong and large polar vortex, a ring of winds that traps cold air over Antarctica and promotes ozone-destroying reactions on stratospheric clouds. NOAA said wave disturbances from lower atmosphere that usually weaken the vortex were weak in August and September. Scientists estimated the hole could have been 1 to 2 million square miles larger if ozone-depleting chemicals remained at year 2000 levels.

The result complicates a simple recovery narrative: the hole can grow sharply in a single season while the layer still recovers over decades. Paul Newman of the University of Maryland and NASA said the annual hole has been forming later in recent years, which he called a sign of healing. That pattern shows weather-driven spikes can mask, but do not erase, the long-term effect of the Montreal Protocol.

The methods note: the report rests on 48 years of observations, with the key limitation that yearly ozone-hole area is strongly influenced by weather, so one large season does not prove the recovery has stalled. The finding matters because ozone shields life from harmful ultraviolet radiation, and the Montreal Protocol's continued enforcement is shown to have limited the hole's size even under conditions favorable to ozone loss.