The ozone hole over Antarctica had one of its largest recorded seasons in 2026, reaching the seventh-largest average extent since monitoring began in 1979, according to data released by NOAA and NASA. From September 7 to October 13, its average area was about 25 million square kilometers—more than twice the size of the United States.
The hole reached its largest area of the year on September 18, at approximately 27.1 million square kilometers. That was about 90% of the record extent measured on September 9, 2000.
Researchers attributed the unusually large hole mainly to atypical weather and a particularly strong polar vortex, the circulation of winds that keeps very cold air over Antarctica. Large-scale weather systems that often weaken and disrupt the vortex were unusually weak in August and September, allowing conditions favorable to ozone loss to persist over a wider area.
Ozone depletion also depends on human-made chemicals containing chlorine and bromine. In the stratosphere, ultraviolet radiation releases these elements, which trigger reactions involving particles in polar stratospheric clouds that break down ozone molecules.
Despite the hole’s size, ozone loss was not as severe as in some record years. Paul Newman, a University of Maryland scientist and former head of NASA’s ozone research team, told Phys.org that if atmospheric levels of ozone-depleting substances were still at their 2000 peak, the hole could have been 3.5 million to 5.6 million square kilometers larger.
International efforts to phase out harmful substances have helped limit the damage. Under the 1987 Montreal Protocol, countries agreed to replace chemicals such as chlorofluorocarbons with less harmful alternatives. NOAA researcher Stephen Montzka said the concentration of chlorine in the Antarctic stratosphere from these substances has fallen by about one-third from its peak in the 1980s.
NOAA researchers track ozone using balloon-borne instruments and a Dobson ozone spectrophotometer, while satellites provide observations dating back to 1979. Measurements over the South Pole showed the year’s lowest ozone concentration on October 17, at 105 Dobson units. The lowest value recorded there was 92 units, in October 2006.
NOAA and NASA say the long-term recovery is continuing, although full recovery will take time because ozone-depleting chemicals can remain in the atmosphere for many decades. Some are also still released gradually from old equipment, landfills and materials containing these compounds. The agencies estimate that the ozone layer will recover by the 2070s.
Sources: Olhar Digital.