Antarctic Ozone Hole Ranks Seventh Largest in 48 Years, Yet Layer Is Healing

The 2026 Antarctic ozone hole ranked as the seventh largest in 48 years of monitoring, but Earth's ozone layer is still on track for long-term recovery, NASA and the National Oceanic and Atmospheric Administration (NOAA) reported. Scientists said an unusually strong polar vortex enlarged the hole, which was not as deep as the record holes of past decades.

The agencies said ongoing measurements show that the Montreal Protocol, the 1987 agreement to replace ozone-depleting substances, continues to drive the recovery.

The key numbers from the 2026 ozone season

• 9.6 million square miles (25 million square kilometers): the average extent of the hole from Sept. 7 to Oct. 13, the peak depletion season.
• 10.5 million square miles (27.1 million square kilometers): the hole's greatest single-day extent this year, reached Sept. 18. The largest hole on record peaked in September 2000.
• 105 Dobson units: the lowest ozone concentration directly over the South Pole this year, measured on Oct. 17 with balloon-borne instruments. The Dobson unit is the standard measure of ozone concentration.
• 92 Dobson units: the lowest value ever recorded over the South Pole, in October 2006. This year's low was shallower.
• About a third: how much chlorine from ozone-depleting substances in the Antarctic stratosphere has declined from its peak, relative to 1980s levels, according to Stephen Montzka of the NOAA Global Monitoring Laboratory.
• The 2070s: when scientists estimate the ozone hole will recover as legacy compounds break down.

Why the hole grew despite the recovery

Paul Newman, a senior scientist at the University of Maryland, Baltimore County, who leads NASA's ozone research team at Goddard Space Flight Center, said the hole has been forming later in the season in recent years, a sign that "the ozone layer is healing." But he said an unusually powerful polar vortex extended depletion this season, letting the hole grow to a size not seen in a decade.

The Antarctic polar vortex helps create the cold conditions in which chlorine and bromine from human-made compounds destroy stratospheric ozone. Amy Butler, a research scientist at the NOAA Chemical Sciences Laboratory, said the vortex was unusually large partly because planetary-scale weather systems that normally rise from the lower atmosphere and break it up were especially weak in August and September.

That weak wave action kept the strongest vortex winds several degrees of latitude farther from the pole, Butler said. The result was a larger area with ideal conditions for ozone loss.

Why it matters: what the findings mean for readers

Stratospheric ozone acts as Earth's sunscreen, helping shield life from harmful solar radiation. NASA noted that this is a different thing from ground-level ozone, an air pollutant commonly produced by human activities.

The 2026 results suggest that a big hole in a given year does not by itself mean recovery has stalled. Newman said the hole could have been 1 to 2 million square miles larger if ozone-depleting substances were as prevalent today as at their peak in 2000. In his account, weather conditions made this year's hole large, while the decline in those substances kept it from being larger.

The substances behind the problem are familiar. Chlorofluorocarbons and related compounds were once widely used in consumer goods such as refrigerators, air conditioners and building insulation. According to NASA, they can linger in the atmosphere or leach out of old products and landfills for many decades, which is why full recovery is expected to take until the 2070s.

How the hole is monitored

NOAA scientists use balloon-borne and ground-based observations from the South Pole Baseline Atmospheric Observatory. Satellite data have been central to tracking the ozone layer since 1979. Instruments aboard NASA's Aura satellite, the NOAA-20 and NOAA-21 satellites, and the Suomi National Polar-orbiting Partnership satellite, which NASA and NOAA operate jointly, all contributed to this year's report.

NASA and NOAA publish the latest status of the ozone layer over Antarctica through NASA's Ozone Watch and NOAA's South Pole Ozone websites.

Around Prague, based on reporting by NASA