The 2026 Antarctic ozone hole was the seventh-largest in 48 years of monitoring, NOAA and NASA reported on November 4, after a strong polar vortex spread it across about 9.6 million square miles. Ozone loss inside the hole was less severe than in record years, and scientists say recovery remains on track for the 2070s.
Key Takeaways
- The 2026 ozone hole ranked seventh-largest in 48 years of monitoring, based on NOAA and NASA’s analysis of its seasonal mean area.
- On September 18, the hole reached 10.5 million square miles (27.1 million square kilometers), about 90% of the size of the record hole of September 9, 2000.
- Ozone over the South Pole bottomed out at 105 Dobson units on October 17, compared with a record low of 92 Dobson units in October 2006.
- NASA scientists estimate the hole would have been 1 to 2 million square miles larger if ozone-depleting chemicals were still at their 2000 peak.
- Chlorine from ozone-depleting substances in the Antarctic stratosphere has fallen by about a third from its 1980s levels.
- Scientists estimate the ozone hole will recover by the 2070s.
NOAA and NASA Rank the 2026 Ozone Hole Seventh in 48 Years
The 2026 Antarctic ozone hole grew unusually large this season. During peak depletion, from September 7 to October 13, it averaged about 9.6 million square miles (25 million square kilometers), more than twice the area of the United States. Its single-day peak came on September 18 at 10.5 million square miles.
Readers may see different rankings for the same hole. Some outlets have called it the biggest in 20 or 25 years, while NOAA and NASA place it seventh in 48 years. The difference comes from what is measured. Rankings built on a single day or a single month in September put 2026 higher, while NOAA and NASA rank holes by their average size across the full depletion season. By that measure, 2026 is the largest hole in a decade but not the largest on record.
Area and Depth Tell Different Stories About the Ozone Layer
The 2026 ozone hole matters less for its width than for what happened inside it. Scientists track two separate measurements, and in 2026 they pointed in different directions.
Area Measures How Far Thin Ozone Spreads
The hole’s area describes how much of the sky over Antarctica falls below a set ozone threshold. A wide hole means thin ozone covered a large region, and weather can push that region outward even when the chemistry behind ozone loss is improving.
Depth Measures How Much Ozone Is Actually Lost
Depth describes how much ozone is destroyed within the hole, and here the 2026 numbers were less severe. NOAA reported that depletion inside the hole was not as deep as in the record-breaking holes of 10 and 20 years ago. Europe’s Copernicus Atmosphere Monitoring Service reached a similar conclusion: total ozone loss was less severe than feared, and ozone levels inside the hole did not fall to exceptionally low values.
The South Pole readings show the gap clearly. Ozone directly overhead reached its lowest point of the year, 105 Dobson units, on October 17. The record low at the station was 92 Dobson units in October 2006. One hundred Dobson units equals a layer of ozone about 1 millimeter thick, roughly the thickness of a dime, if compressed at sea-level conditions.
A Strong Polar Vortex Widened the Hole
The 2026 ozone hole grew large mainly because of weather. The stratospheric polar vortex, a seasonal ring of wind around Antarctica, traps frigid air and allows the polar stratospheric clouds that drive ozone destruction to form. NOAA research scientist Amy Butler explained that large-scale weather systems, which usually rise from the lower atmosphere and break up the vortex, were especially weak in August and September. That kept the vortex’s strongest winds several degrees of latitude farther from the South Pole, widening the area where ozone could be destroyed.
The 2025 season shows how much weather alone can change the result. A weaker-than-normal vortex in August 2025 helped make that year’s hole the fifth-smallest since 1992. Just one year later, a strong vortex produced one of the larger holes on record. Researchers are still studying how climate change may affect the vortex’s strength, and that question remains open.
The Montreal Protocol Is Still Doing Its Work
The 2026 ozone hole also shows how much the Montreal Protocol has changed the conditions behind it. Adopted in 1987 and in force since 1989, the treaty reached universal participation in 2009 and committed countries to replacing chlorofluorocarbons and other ozone-depleting substances. NOAA senior scientist Stephen Montzka said chlorine in the Antarctic stratosphere from those substances has fallen by about a third from its 1980s levels.
That reduction shows up in this year’s numbers. Paul Newman, a senior scientist at the University of Maryland and longtime leader of NASA’s ozone research team, estimated the 2026 hole could have been 1 to 2 million square miles larger if ozone-depleting substances were as common now as at their 2000 peak. Newman also pointed to another sign of healing: in recent years, the hole has been forming later in the season.
Because older chemicals linger in the atmosphere for decades and continue to leak from old refrigerators, insulation, and landfills, recovery is slow. Scientists estimate the ozone hole will recover by the 2070s.
Satellites and South Pole Balloons Track the Recovery
Measurements of the 2026 ozone hole come from both orbit and the ice. NOAA staff at the South Pole Baseline Atmospheric Observatory launch weather balloons carrying ozonesondes and use a Dobson Ozone Spectrophotometer to measure ozone overhead. The South Pole is a long-running scientific outpost, home to everything from atmospheric monitoring to Nobel-winning research that turned Antarctic ice into a neutrino telescope.
Satellites have tracked the ozone layer since 1979, and NASA’s Aura satellite, the NOAA-20 and NOAA-21 satellites, and the jointly operated Suomi NPP satellite all contributed to this year’s monitoring. Together, these records separate a single season’s weather from the long-term chemical trend, which is how scientists can call 2026 a large hole and a recovering ozone layer at the same time.
FAQs
Is the Ozone Hole Getting Worse?
No. The 2026 hole was large because of a strong polar vortex, but ozone loss inside it was less severe than in record years. NOAA and NASA say the long-term recovery remains on track.
Why Was the Ozone Hole So Big in 2026?
Weak large-scale weather systems in August and September let the polar vortex stay strong and wide, which expanded the area where ozone could be destroyed. The cause was weather, not a rise in ozone-depleting chemicals.
When Will the Ozone Layer Recover?
Scientists estimate the Antarctic ozone hole will recover by the 2070s. Recovery is gradual because older ozone-depleting chemicals persist in the atmosphere for decades.
What Is the Montreal Protocol?
The Montreal Protocol is a 1987 international treaty that phases out ozone-depleting substances such as chlorofluorocarbons. It entered into force in 1989 and has been ratified by every country since 2009.
