Three numbers explain the 2026 Antarctic ozone hole

Total-column ozone over Antarctica and the Southern Ocean on 18 September 2026, the day of the largest mapped area that year. NASA Earth Observatory published the map on 9 November. Map by Lauren Dauphin, NASA Earth Observatory, using NASA Ozone Watch data. Original image unchanged. NASA map and source · NASA image use terms

The warm colours over Antarctica on this map show where the ozone layer thinned on 18 September. NASA and NOAA reported three figures for the 2026 season. They describe the largest area on a single day, the average area over several weeks and the amount of ozone over a single station. Reading them together explains how a wide ozone hole can occur in a year when long-term recovery remains on track, according to the agencies. NASA and NOAA assessment

27.1 million square kilometres on one day

NASA’s 9 November Earth Observatory feature shows the day of the greatest area, 18 September 2026. Start with the key at the bottom. The line at 220 Dobson units marks the threshold the researchers use to measure the ozone hole’s extent. Warm colours indicate less ozone in the atmospheric column, and blue indicates more. Scientists count the area below the threshold across many columns. The red and orange are colours assigned to values in a dataset. Ozone is still present over the region. Earth Observatory map · Dated Ozone Watch record

25 million square kilometres across the peak season

The second number is the mean extent from 7 September to 13 October. NASA’s Earth Observatory uses that window to rank 2026 seventh by mean area in 48 years of monitoring. An average across weeks helps readers compare seasons, while the biggest day tells them how far the affected region extended at one point. If you open the comparison farther down NASA’s page, look at its date and caption. That set of maps uses the day of deepest depletion in each year. The top map uses the day of greatest area. NASA’s comparison and method

105 Dobson units above the South Pole on 17 October

NOAA scientists reported a minimum of 105 Dobson units directly above their South Pole station on 17 October. A Dobson unit describes the amount of ozone in a column from the surface to the top of the atmosphere. It answers a different question from square kilometres. If you are comparing two reports, keep the station name beside the number. A value over the South Pole and a map across Antarctica can both describe the same season while covering different places. NASA and NOAA assessment · Dobson unit guide

Read the weather and the long record together

NASA and NOAA attribute the large 2026 area in part to an unusually strong polar vortex. It kept conditions cold enough for chemicals to deplete ozone across a large region. Their longer-term recovery assessment draws on many years of observations and the phase-down of ozone-depleting substances under the Montreal Protocol. British Antarctic Survey’s long record at Halley helped its scientists identify the ozone hole in 1985. In South Africa, the national weather service’s 2023/24 report lists total-ozone observations at Irene and Springbok. Keep the area, time window and observing location with each figure so you can compare the right records. NASA and NOAA assessment · British Antarctic Survey · South African Weather Service report

For another way to trace an image back to its instrument and date, see PING’s guide to NASA’s Artemis II archive.