WMO logs a second consecutive Antarctic ozone hole well below the 1990-2010 average
The World Meteorological Organization's new bulletin puts the Antarctic hole below its long-term average for a second year running, and the researchers reading the same data disagree about whether the recovery is on schedule.
The Scientist · Science desk
What happened
- The WMO's Ozone Bulletin ranks the 2025 Antarctic ozone hole as the fourth or fifth smallest since severe depletion patterns were first observed in 1992.
- Ozone was below average across a band from Greenland and Europe through Central Asia to northern Japan and Kamchatka, which the report attributed to a strong Arctic winter vortex in January and February 2025.
- Ozone usually reaches its annual low in October, but in 2025 the minimum arrived in September.
Why it matters
- What it limits constraint The observing network has lost about 15% of its stations. That same monitoring is what caught CFC-11 emissions continuing to 2018 and HFC-23, so detection of the next phase-out violation now rests on fewer instruments.
- What doesn't add up contradiction WMO's secretary-general expects full recovery within several decades, while UCLA's Suzanne Paulson says there have been no major improvements in recent years. The same bulletin supports either summary, so a citation of it depends on who is quoted.
- Who's exposed exposure Populations in parts of Europe are taking up to 20% more UV than in the mid-1990s because of thinner cloud cover, so the health risk the ozone column guards against is rising there even as the column recovers.
- What it sets up precedent Because three or four years since 1992 still had smaller holes, the recovery case rests on two consecutive below-average years, and one weather-driven bad year will be read as backsliding on the same basis.
Next story · Science · Oct 8
WMO forecasts record Pacific warmth of 3.7C above normal as El Niño builds toward a December peakConfirmed3 publishers
Fourth or fifth smallest since 1992 means three or four years in that record had smaller holes than 2025 [21]. The new information is the pair: two years running in which both the depth and the extent of the hole sat significantly below the 1990-2010 average [2].
Size in any single year depends heavily on large-scale meteorological transport, the circulation that produces springtime depletion over Antarctica almost every austral winter and, in the Northern Hemisphere, every five to 10 years [3]. Suzanne Paulson, a professor at UCLA, told Scientific American that the hole has been healing more slowly than scientists predicted it might [24]. "It does go up and down every year, so any one year doesn't really tell you a whole lot," she said [4]. "It certainly hasn't gotten worse in recent years, but for the most part, we haven't really seen major improvements" [23].
The WMO's own framing is warmer. "This is an environmental success story. Since 2000, the ozone layer has been recovering, and we can expect full recovery within several decades," said WMO Secretary-General Celeste Saulo [25]. Laurence Rouil, director of the Copernicus Atmospheric Monitoring Service, said in a statement that "while we have seen its area increase rapidly in early September this year, other indicators remain close to historical averages" [9].
The two published accounts of the same bulletin do not use the same reference period. Phys.org reported the comparison against the 1990-2010 average [2]. Scientific American reported the hole as significantly smaller than its average size between 1990 and 2020 [26]. A window that runs to 2020 takes in a decade the shorter one leaves out, so the two comparisons are not interchangeable.
Regulatory action here has depended on measurement. Atmospheric monitoring caught unexpected emissions of CFC-11, which continued until 2018, and of HFC-23, and the WMO says such monitoring remains essential to support targeted regulatory action by national authorities [12]. The ground-based network supplying total column ozone observations has thinned from around 130 active stations in the early 2000s to 110 today, about 20 fewer, a drop of roughly 15% [11][22]. The next test of that network is the Kigali Amendment, whose 10th anniversary is this year's World Ozone Day theme, and which phases down HFCs, some of which trap thousands of times more heat than carbon dioxide [14][13].
Ozone recovery does not by itself mean less ultraviolet light at the ground. The shield is thin: about 90% of atmospheric ozone sits in the upper stratosphere, and brought down to the surface it would form a layer roughly 3 millimetres thick [17]. In some parts of Europe UV radiation has risen by as much as 20% since the mid-1990s, and ground measurements attribute that primarily to reduced cloud cover and longer annual sunshine duration [15]. Higher exposure means greater risk of skin cancer and other UV-related diseases among exposed populations [20]. The Bulletin's response is that "targeted and effective UV protection measures are of paramount importance" [16].
What to watch
- Whether the 2026 hole stays below the 1990-2010 average; a third year would begin to separate trend from meteorology.
- Whether the ground station count stabilises at 110 or keeps falling as Dobson and Brewer instruments retire.
- Whether monitoring turns up new unexpected HFC-23 or CFC emissions during Kigali's second decade.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence60
- Adoption45
- Hype gap+25
- Incentives65
- Confidence58
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The WMO Ozone Bulletin said the 2025 ozone hole ranked as the fourth or fifth smallest since severe depletion patterns were observed in 1992.
- [2]
2025 was the second consecutive year that both the depth and the extent of the Antarctic ozone hole were significantly below the 1990-2010 average.
- [3]
Year-to-year fluctuations in the hole are influenced by large-scale meteorological transport conditions, which drive springtime ozone depletion almost every austral winter above Antarctica and every five to 10 years in the Northern Hemisphere.
- [4]
"It does go up and down every year, so any one year doesn't really tell you a whole lot," said Suzanne Paulson, a professor at the University of California, Los Angeles, referring to seasonal fluctuations in the size of the ozone hole.
- [5]
In the Northern Hemisphere, total column ozone in 2025 was below average in a large region extending from Greenland and Europe to Central Asia, northern Japan and the Kamchatka Peninsula in the Russian Federation.
- [6]
The report attributed the Northern Hemisphere ozone anomaly to a strong Arctic winter vortex in January and February 2025.
- [7]
The Montreal Protocol on Substances that Deplete the Ozone Layer phased out chemicals such as chlorofluorocarbons once found in refrigeration, firefighting foam and other common uses.
- [8]
The ozone hole was discovered in the 1980s and attributed to human-made chlorofluorocarbons; nations signed the Montreal Protocol, an international treaty banning CFCs, in 1987.
- [9]
"While we have seen its area increase rapidly in early September this year, other indicators remain close to historical averages," said Laurence Rouil, director of the Copernicus Atmospheric Monitoring Service, in a statement.
- [10]
October is typically the month with the least ozone, but in 2025 ozone hit a low in September.
- [11]
The number of active ozone observing stations, traditionally relying on Dobson and Brewer spectrophotometers, has gradually decreased from around 130 in the early 2000s to 110 today.
- [12]
There have been unexpected emissions, for instance of CFC-11 until 2018 and of HFC-23, which is why atmospheric monitoring remains essential to support targeted regulatory actions by national authorities.
- [13]
The 2016 Kigali Amendment provides for a phasedown of hydrofluorocarbons, some of which trap thousands of times more heat than carbon dioxide while remaining in the atmosphere for a much shorter time.
- [14]
The WMO Ozone Bulletin was released for World Ozone Day on Sept. 16, whose theme this year is Global Action for a Cooler Planet, marking the 10th anniversary of the Kigali Amendment.
- [15]
Since the mid-1990s, UV radiation has increased by as much as 20% in some parts of Europe, and ground-based measurements show this has been driven primarily by a reduction in cloud cover and an accompanying increase in annual sunshine duration.
- [16]
The Bulletin states that "in light of this trend, targeted and effective UV protection measures are of paramount importance".
- [17]
About 90% of atmospheric ozone resides in the upper stratosphere, and if all of it were brought down to Earth's surface the resulting layer of pure ozone would be only approximately 3 millimeters thick.
- [18]
The WMO Global Atmosphere Watch network provides the ground-based total column ozone observations required to monitor ozone and understand long-term changes.
- [19]
Measurements over the past decades show a significant increase in the number of days with high UV index values.
- [20]
Higher UV exposure means a greater risk of skin cancer and other UV-related diseases among exposed populations.
- [21]
A ranking of fourth or fifth smallest since 1992 implies that three or four years in that record had smaller ozone holes than 2025.
- [22]
The fall from around 130 stations to 110 is about 20 fewer stations, a decline of roughly 15%.
- [23]
"It certainly hasn't gotten worse in recent years, but for the most part, we haven't really seen major improvements," said UCLA professor Suzanne Paulson.
- [24]
Paulson cautions against overoptimism, saying the hole has been healing at a slower rate than scientists had predicted it might.
- [25]
"This is an environmental success story. Since 2000, the ozone layer has been recovering, and we can expect full recovery within several decades," said WMO Secretary-General Celeste Saulo.
- [26]
Scientific American reported that the WMO finds the hole "significantly" smaller than its average size between 1990 and 2020.
Sources
2 independent publishers whose own reporting we read for this story.
- phys.orgIn 2025, the ozone hole shrunk to one of its smallest sizes in decades
1 article · September 18, 2026
- scientificamerican.comThe hole in the ozone layer is healing, but extreme weather may be slowing progress down
1 article · September 15, 2026
Topics and entities
Topics
- Ozone and refrigerant policy
- UV radiation and health
- Ozone layer recovery
- Atmospheric monitoring
Entities
- Kigali Amendment
- University of California, Los Angeles
- WMO Global Atmosphere Watch
- Copernicus Atmosphere Monitoring Service
- Montreal Protocol
- Celeste Saulo
- World Meteorological Organization