Antarctica’s ozone hole was the seventh-largest in 48 years of monitoring this year, NASA and NOAA reported November 4. Scientists attributed the unusually large area to weather conditions, while saying the ozone layer’s long-term recovery remains on track.
The hole averaged about 9.6 million square miles from September 7 through October 13, more than twice the area of the United States. Its greatest extent came September 18, at about 10.5 million square miles.
The measurements concern ozone high in the stratosphere, where it helps protect living things from harmful solar radiation. That protective layer is different from ground-level ozone, which is an air pollutant.
A powerful polar vortex helped sustain the cold conditions that allow chlorine and bromine compounds to destroy ozone over Antarctica. The agencies said this year’s weather extended the season of ozone loss.
Area alone does not describe every aspect of the hole. NASA reported that ozone concentrations were not depleted as deeply as in some earlier years; the lowest South Pole measurement was 105 Dobson units on October 17, compared with 92 in October 2006.
Scientists track the changes with satellite observations and instruments carried by weather balloons. Those measurements allow researchers to distinguish the hole’s size from the amount of ozone remaining within it.
Restrictions on ozone-depleting chemicals under the 1987 Montreal Protocol have reduced the substances responsible for the damage. The agencies said the 2026 hole would have been larger without those reductions.
Recovery still takes decades because older chemicals persist in the atmosphere and in products such as refrigeration equipment and insulation. NASA’s assessment places Antarctic recovery in the 2070s, even as individual years continue to vary with weather.