The 2026 ozone hole: large, but not as deep as others
· BehindLines newsroom
NASA’s Earth Observatory published its assessment of the 2026 Antarctic ozone hole on 9 November. Measured by its average area during the peak period, from 7 September to 13 October, it ranks seventh in 48 years of monitoring. However, it is not as deep as other large holes already recorded.
Two different measurements
Scientists call a “hole” the area where ozone concentration falls below 220 Dobson units, a historical threshold. The word is a metaphor: no region is empty of ozone. NASA distinguishes the extent of the hole from its depth, meaning the lowest values measured. Records never fall in the same year: the largest hole dates from 2006, the deepest from 1994, at 73 Dobson units on 30 September.
In 2026, an unusually strong Antarctic polar vortex created conditions favorable to ozone destruction over a large area. The maximum extent was reached on 18 September.
A neighbouring European reading
The Copernicus Atmosphere Monitoring Service (CAMS) had published a similar, but not identical, assessment in mid-September. The hole exceeded 15 million km² at the end of August, more than Antarctica (14.2 million km²), then reached about 25 million km² on 12 September, nearly 5 million above the average for the period. According to CAMS, other indicators, such as the minimum value of the ozone column and the mass deficit, stayed close to their averages. These September figures describe a provisional state of the season. They cannot be compared directly with NASA’s ranking, which rests on an average over several weeks.
Recovery over the long term
NASA attributes differences from one year to the next to the temperature and circulation of the stratosphere: the colder it is, the more the hole spreads. Human-made chlorine and bromine compounds remain responsible, and models indicate that their concentrations will stay above the pre-1980 level until well into this century. A first direct satellite evidence of recovery was reported in 2018, and CAMS notes that the holes of recent years have been smaller and shorter-lived. The 2026 ranking describes one season, not the long-term trajectory.