WASHINGTON, DC — The Antarctic ozone hole expanded to an unusually large size in 2026, and NOAA and NASA scientists say a powerful polar vortex helped drive the change. Researchers say the season produced the seventh-largest ozone hole in 48 years of monitoring, marking the biggest extent seen in a decade.
Even with that surge, scientists say the broader ozone layer remains on a path toward recovery by the end of the century. The latest measurements point to a season shaped by unusual atmospheric conditions rather than a reversal of the long-term healing trend.
Paul Newman, a senior scientist at the University of Maryland and longtime leader of NASA’s ozone research team at Goddard Space Flight Center, said the annual hole has been forming later in recent years, which suggests recovery is underway. But he said this year’s vortex kept depletion going longer than usual.
How large the ozone hole became during the 2026 season
During the peak ozone depletion period from Sept. 7 through Oct. 13, the hole covered about 9.6 million square miles. NOAA and NASA said that is more than twice the size of the United States, underscoring how extensive the depleted area became during the heart of the season.
The ozone hole reached its largest size on Sept. 18, when it stretched to roughly 10.5 million square miles. Scientists said that was about 90% of the size of the largest ozone hole ever recorded, which was observed on Sept. 9, 2000.
The season was notable not only for its size but also for the length of time ozone depletion persisted. Researchers said the hole’s growth reflected atmospheric conditions that gave the depleted region more room to spread across the Antarctic.
Why the polar vortex mattered so much this year
Scientists say ozone depletion happens when human-made chemicals containing chlorine and bromine enter the atmosphere. Air currents move those gases into the stratosphere, where ultraviolet radiation breaks them apart and releases compounds that destroy ozone.
Those chemicals then react with particles in polar stratospheric clouds, which accelerates the loss of ozone. Amy Butler, a research scientist at NOAA’s Chemical Sciences Laboratory, said the polar vortex was unusually large this year.
Butler said weak atmospheric wave activity kept the strongest vortex winds farther from the South Pole, creating a larger area where conditions favored ozone destruction. That setup helped the hole expand farther than it otherwise might have during the season.
Scientists say the 2026 season was serious but not the worst on record
NOAA scientists emphasized that this year’s ozone loss was not as severe as the record-breaking seasons seen 10 to 20 years ago. Even with the unusually large size, researchers said the 2026 hole did not return to the most extreme levels measured in the past.
The hole reached its lowest ozone concentrations of the year on Oct. 17, according to the monitoring data. That reading marked the low point for the season and helped define how strong the depletion became at its peak.
Researchers framed the numbers as a reminder that short-term atmospheric swings can still produce big annual changes, even while the longer recovery process continues. The size of the hole this year reflected those temporary conditions more than a lasting setback.
What the latest ozone readings say about long-term recovery
Despite the large 2026 ozone hole, scientists say the overall trend remains encouraging. The later seasonal timing of the hole in recent years is one of the signals they point to when describing a recovering ozone layer.
Monitoring also shows that international action has made a difference. Efforts to replace ozone-depleting substances such as chlorofluorocarbons with less harmful alternatives are helping the atmosphere heal over time.
NOAA and NASA said the continued observation of the Antarctic ozone hole remains important because it shows how the atmosphere responds both to dangerous chemicals and to the changing dynamics of the polar vortex. The long-term picture, they said, still supports recovery by the end of the century.
Why the Antarctic ozone hole still matters for U.S. readers
The ozone layer helps protect life on Earth from harmful ultraviolet radiation, so changes over Antarctica remain a global science and environmental concern. U.S. agencies have tracked the Antarctic hole for decades because it offers one of the clearest ways to measure that protection.
This year’s readings show that the atmosphere can still produce sharp seasonal swings, even as the planet moves away from the era of the worst ozone loss. Scientists say that combination makes continued monitoring essential.
For readers in the United States, the key takeaway is that the recovery story is still intact. The 2026 season was unusually large, but NOAA and NASA say the broader system is still expected to heal over the decades ahead.