Antarctic ozone hole grew to seventh-largest in 48 years in 2026, NOAA and NASA report

The hole in the ozone layer over Antarctica was the seventh-largest by area in 48 years of monitoring this year, NOAA and NASA reported on November 4, 2026. From September 7 to October 13, the peak of the depletion season, it averaged about 9.6 million square miles (25 million square kilometers), up from the 7.23 million square miles (18.71 million square kilometers) NOAA reported for 2025.

The agencies put this year's size down to atmospheric conditions and say the ozone layer remains on track for long-term recovery. NOAA adds that without the international cuts in ozone-destroying chemicals, the hole would have been bigger.

A strong vortex, after a weak one

The polar vortex is a ring of wind that forms around Antarctica each season and traps the very cold air that polar stratospheric clouds need. On those clouds, chlorine and bromine released from human-made compounds can destroy ozone. This year the vortex was unusually large. Amy Butler of NOAA's Chemical Sciences Laboratory said the huge weather systems that normally climb from the lower atmosphere and break the vortex apart were especially weak in August and September. That kept its strongest winds several degrees of latitude farther from the South Pole and widened the area where ozone could be lost.

Last year ran the other way. NOAA said in 2025 that a weaker-than-normal vortex that August helped keep temperatures above average and likely contributed to a smaller hole. NASA's Ozone Watch records show how widely the size swings from one year to the next.

On those records, no year since 2015 has reached 2026's figure on either measure, which fits Paul Newman's description of a hole grown “to proportions we haven’t seen in a decade.” Newman is a senior scientist at the University of Maryland, Baltimore County, and longtime leader of NASA's ozone research team.

Wide, but not as deep

The hole hit its largest single-day extent on September 18, at 10.5 million square miles (27.1 million square kilometers), about 90% of the record set on September 9, 2000. Its depth was less extreme. NOAA's instruments at the South Pole recorded a low of 105 Dobson units on October 17. Last year's low was 147, on October 6, and the lowest value ever recorded there was 92, in October 2006.

Scientists define the hole as the area where ozone falls below 220 Dobson units. One hundred units would make a layer 1 millimeter deep, about the thickness of a dime, if compressed at standard temperature and sea-level pressure.

Why scientists still see healing

The annual ozone hole has been forming later in the season in recent years, which tells us the ozone layer is healing.

Newman also estimated that this year's hole could have been 1 million to 2 million square miles larger if ozone-depleting substances were as prevalent as at their 2000 peak. Stephen Montzka of NOAA's Global Monitoring Laboratory said chlorine from those substances in the Antarctic stratosphere has declined from its peak by about a third, relative to 1980s levels. The agencies credit controls set by the 1987 Montreal Protocol.

The wording on the recovery date has changed. This year's reports say scientists estimate the hole will recover by the 2070s, while NOAA's 2025 release said around the late 2060s. Neither of this year's reports explains the difference or says whether the estimate was revised, so the wording alone does not show a later date.

The ozone layer shields life from harmful solar radiation. NOAA says reduced ozone lets more ultraviolet rays reach the surface, which can damage crops and increase cases of skin cancer and cataracts. The recovery is slow because chlorofluorocarbons and related compounds from old refrigerators, air conditioners, insulation and landfills can linger for decades.

What comes next

Both agencies publish current readings, on NASA's Ozone Watch and NOAA's South Pole ozone page. NASA's annual tables, last updated on November 3, run through 2025.