WASHINGTON (dpa-AFX) - The Antarctic ozone hole reached its maximum single-day extent for the year on September 18, measuring 10.5 million square miles (27.1 million square kilometers), according to data from NASA and NOAA.
In 2026, the ozone hole ranked seventh largest by area in 48 years of monitoring, but it was not as deep as other large holes on record.
The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which damages DNA in plants, humans and animals, and leads to sunburns and skin cancer. In 1985, British Antarctic Survey scientists reported that Earth's natural sunscreen was thinning dramatically over Antarctica each spring. NASA satellite instruments revealed the continental scale of this Antarctic ozone thinning, and it came to be known as the ozone hole.
Scientists use the word hole as a metaphor for the area in which ozone concentrations drop below the historical threshold of 220 Dobson Units.
The maximum depth of the ozone hole in 1979, when the series of measurements began, was 194 Dobson Units, or DU.
The deepest ozone hole occurred in 1994, when concentrations fell to just 73 DU.
Year-to-year fluctuations in area and depth are caused by variations in stratospheric temperature and circulation. Colder conditions result in a larger area and lower ozone values in the core of the hole.
That was the case in 2026, when an unusually strong Antarctic polar vortex created ideal conditions for ozone depletion over a large area. Measured by its mean size from September 7 to October 13, which is peak ozone depletion season, the 2026 hole was the seventh largest in 48 years of monitoring, NASA said in a press release. However, it was not as deep as other large holes on record. The map at the top of this page shows the hole on September 18, the day of its annual maximum area.
The ozone hole opened the world's eyes to the global effects of human activity on the atmosphere. Scientists learned that chlorofluorocarbons - long-lived chemicals that had been used in refrigerators and aerosol sprays since the 1930s - had a dark side.
In the layer of the atmosphere closest to Earth, CFCs circulate for decades without degrading or reacting with other chemicals. When they reach the stratosphere, however, their behavior changes. In the upper stratosphere (beyond the protection of the ozone layer), ultraviolet light causes CFCs to break apart, releasing chlorine, a very reactive atom that repeatedly catalyzes ozone destruction.
The global recognition of the destructive potential of CFCs led to the 1987 Montreal Protocol, a treaty phasing out the consumption and production of ozone-depleting chemicals. Scientists estimate that about 80 percent of the chlorine in the stratosphere today comes from human, not natural, sources. Human-produced bromine compounds, which are far less abundant but much more destructive to ozone, also contribute to the Antarctic ozone hole.
Models suggest that the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre-1980 levels until later in the 21st century.
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