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Ozone over Antarctica · 1979–2026
The hole over Antarctica
Every September a hole opens in the ozone layer above the South Pole. By December it closes. Here is every one of those springs since 1979, from daily satellite maps, up to this one.
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It is still open
18.5million km² below the hole’s thresholdThat is more than the whole of Antarctica, about 14 million km². For this date, only six or seven springs since 1979 had a larger hole on these maps.
On these maps this year’s hole was largest on 20 September, at 26.4 million km². NASA’s own measurements put the peak on 18 September at 27.1 million km², and rank 2026 seventh largest in 48 years by its average size from 7 September to 13 October.
The 2026 maps come from a different satellite record from the earlier years; in the seven years where both exist, it shows the hole about 0.6 million km² larger on a typical day.
What is missing
Ozone is spread thinly through the air, most of it in the stratosphere, roughly 15 to 35 km up. Bring all of it above your head down to the ground and it would make a layer about 3 millimetres thick.
Scientists count it in Dobson units: 100 units make 1 mm. Below 220 units, 2.2 mm, they call it the hole. On 13 November the thinnest point is 155 units. The lowest on these maps, 86 units, came in 2005.
That thin layer absorbs most of the sun’s ultraviolet-B, the part that burns skin, damages eyes and harms plants and plankton. Less ozone lets more of it through.
Why there, and why in spring
Through the polar winter a ring of strong wind circles Antarctica and keeps the air inside it apart. That air becomes the coldest in the atmosphere. Below about −78 °C, thin clouds form high in the stratosphere.
On those clouds, chlorine from CFCs, gases once used in fridges, spray cans and foam, is changed into forms that sunlight breaks apart. When the sun returns in late August and September, the freed chlorine destroys ozone fast. The hole grows.
In November and December the ring of wind weakens, air rich in ozone flows back in, and the hole fills. Watch the warm band around it: a collar of ozone-rich air that gathers along the edge of the ring of wind.
Before the hole
The first spring with daily satellite maps. On only a handful of days does any patch over Antarctica drop below 220 units, and never by much.
Someone notices
In May 1985 three scientists of the British Antarctic Survey, Joe Farman, Brian Gardiner and Jonathan Shanklin, reported in Nature that spring ozone over Antarctica had fallen considerably
. They measured it from the ground, at the Halley and Faraday stations.
That October the hole on these maps reached 17.3 million km².
The world signs
In September 1987 governments signed the Montreal Protocol to cut the gases destroying ozone. It came into force in 1989 and was strengthened again and again, until the production of CFCs was phased out. By 2009 every country in the United Nations had ratified it.
The hole kept growing anyway. CFCs stay in the air for decades, so the chlorine already up there went on working.
The worst years
The ozone-destroying gases over Antarctica peaked around the year 2000. On 10 September that year the hole on these maps reached its largest: 29.4 million km², bigger than North America.
In 2006 the ozone above the South Pole itself fell to 91 units, under 1 mm.
A warm year
In early September 2019 the stratosphere over Antarctica suddenly warmed and the ring of wind weakened. On these maps the hole stayed small, 10.5 million km² at most, the smallest since the early 1980s.
Nothing about the chlorine changed that year. The weather did.
Four large holes in a row
From 2020 to 2023 each hole grew past 24 million km², and several lasted into the middle of December. Cold, steady polar winters did much of it; in 2020, smoke from Australia’s bushfires added to the ozone loss. Here is 2020 on 13 December, a date by which most holes have gone.
Small, then large again
In 2025 the hole was one of the smallest in recent years. It shrank quickly in the first half of November, but a small area of depleted ozone persisted until the end of the month. Copernicus dates its closure to 30 November; the WMO reports 1 December. A year later, 2026 brought one of the largest.
That swing is why headlines say “healing” one year and “one of the biggest” the next. Both are true. The question is what lies underneath.
Pick a spring
Choose any year since 1979, or the year you were born. Drag the globe to turn it.
Each line is one spring, from 1 August to 14 December. The dashed line is the area of Antarctica.
Is it getting smaller?
Before computing the September averages, I wrote down a test: if the hole is shrinking, its average size over 1–15 September should fall from 2001 to 2025, clearly enough that the trend could not be chance. Early September is when the chlorine matters most and the late-spring weather least.
Average size over 1–15 September each year. Filled dots: the years tested, with the trend and its 95% range. Ringed dot: 2026, from the other satellite record.
The test failed. The trend points down, by about 0.07 million km² a year, but the range of likely trends still includes no change at all. The same check over NASA’s window, 7 September to 13 October, failed too; that one was not blind, because I had already seen NASA’s averages for those dates.
Over 1–15 September the last ten springs averaged 17.0 million km², against 18.3 million in 2001–2010, about 7% smaller. One year’s weather moves the hole by far more than that. The 2026 UN assessment of the ozone layer says the same: the hole’s area, depth and length still vary a lot from year to year, mainly because of the weather high above Antarctica.
The recovery shows up in the cause. Over Antarctica, the combined ozone-destroying power of the gases peaked in 2001; by 2024 it had fallen 13%, which is 28% of the fall needed to get back to its 1980 level. NASA estimates that this year’s hole would have been about 3.5 million km² larger if the gases were still as abundant as in 2000.
People at the edge
The hole is not only over ice. When the ring of wind stretches, its edge swings over the southern tip of South America. On 6 October 2003 Ushuaia, Punta Arenas and Stanley were all under it.
Days each spring when the ozone over Punta Arenas fell below 220 units (nearest map point).
Ushuaia had up to 14 such days a spring, in 2000 and 2003. On those days the sun burns faster. Hobart and Cape Town, the big cities nearest the pole in Australia and Africa, never came under the hole on these maps.
What the ban avoided
Scientists have modelled a world where the gases were never controlled and kept growing by 3% a year. By 2065 two-thirds of the planet’s ozone would have been gone, compared with 1980, and the sunburning ultraviolet of a northern mid-latitude summer would have more than doubled by 2060.
For the United States alone, the US Environmental Protection Agency expects the treaty to prevent about 443 million cases of skin cancer and 63 million cataracts among Americans born between 1890 and 2100.
When it should close for good
If the rules hold, the ozone over Antarctica should be back to its 1980 level during the 2060s, according to the 2026 UN assessment; NASA says the hole will recover by the 2070s. The average for the rest of the world, between 60°S and 60°N, should get there around 2040.
Until then the hole will keep opening each September, bigger in cold years and smaller in warm ones, a little less on average each decade. The gases that cause it are banned and falling. The size of the hole is the slowest part to show it.