Pick a year and see the ozone layer then
The map shows a typical late-September day over the South Pole for the selected year. It is redrawn from that year's observed (or projected) ozone-hole area and minimum column. The cards show the matching state of the atmosphere. After 2025, global ozone, CO₂, temperature and N₂O follow the scenario chosen in the bottom bar. Antarctic values depend on chlorine and are the same in every scenario.
What the instruments recorded, and what comes next
Solid lines and dots are measurements. Dashed lines past 2025 are projections, with a shaded band for typical year-to-year weather noise. The blue vertical line tracks the slider. Hover over or tap any chart to read the values.
Antarctic ozone hole area
Mean area below 220 DU, 7 Sep – 13 Oct · million km² · NASA Ozone Watch
1995: no satellite coverage. 2026: provisional mean for 7–29 Sep. Antarctica itself is about 14 M km². Band = ±1σ year-to-year spread around the central projection (excludes model uncertainty).
Depth of the hole
Mean of the daily minimum column, 21 Sep – 16 Oct · Dobson Units (DU) · NASA Ozone Watch
Deepest season: 92 DU (1994). Lowest single day: 73 DU on 30 Sep 1994. 2026: mean for 21–29 Sep only.
Halley station, October mean ozone (since 1956)
British Antarctic Survey Dobson record that revealed the hole in 1985 · DU
Hollow dots: BAS "broadly comparable satellite values" for Halley, used where the Dobson record has gaps (2017–18, 2021–25).
Near-global ozone (60°S–60°N)
Annual mean total column vs the 1964–1980 average · % · NASA merged satellite record (SBUV MOD), baseline set so 2017–20 = −2% as in WMO 2022
The 1992–93 dip is Mount Pinatubo's volcanic aerosol. 1979–81 sat near solar maximum (≈ +1%). Hollow dots 1971–72: early Nimbus-4 BUV satellite, less certain calibration.
Arctic spring ozone
March mean total column, 60–80°N · DU · NASA merged satellite record
The Arctic vortex is warmer and less stable than the Antarctic one. Large losses happen only in cold years: 1997, 2011 and 2020.
Ozone-destroying chlorine + bromine (EESC)
Equivalent effective stratospheric chlorine · ppt · NOAA ODGI (1992–2024) + reconstruction/projection
Solid 1992–2024: NOAA, derived from surface measurements. Dashed: reconstructed shape (before 1992) and projection. Dotted: 1980 benchmarks implied by NOAA's ODGI. Return: mid-latitudes ~2045–47, Antarctica ~2066–70.
CFC-11 and CFC-12 in the air
Global surface mean · parts per trillion · NOAA HATS
Dashed before 1978: reconstructed. CFC-12 lasts about 100 years in the atmosphere and CFC-11 about 50, so the decline is slow. The 2012–2018 slowdown in CFC-11's fall was traced to unreported production.
UV under the hole (estimated)
Clear-sky noon UV index at Halley (75.6°S) in mid-October, derived from the October ozone column
UVI ≈ 12.5·cos2.42(67°)·(O₃/300)−1.23 × 1.4 for snow reflection. The sun is low in October at 75°S, so absolute values stay modest, but deep holes roughly triple UV. Further north (Palmer, Ushuaia) the same loss gives much higher UV.
Table view: key years
Why a few parts per billion of chlorine matter
Ozone is constantly made and destroyed by sunlight, in balance. CFCs, halons and other long-lived gases add an extra destruction path. In the stratosphere, UV light breaks them apart and frees chlorine and bromine atoms. These act as catalysts: each atom destroys thousands of ozone molecules before it is locked away.
Where the ozone is
Ozone is measured in Dobson Units: 300 DU is a 3 mm layer of pure ozone at sea-level pressure. A 1% loss of ozone raises sunburn-causing (erythemal) UV by roughly 1.1–1.2%.
The chlorine catalytic cycle and the polar twist
Bromine is about 60 times more destructive per atom than chlorine, which is why halons count heavily in EESC. Nitrous oxide (N₂O) works through a separate nitrogen-oxide cycle and is not controlled by the Montreal Protocol.
From discovery to diplomacy to recovery
Click any milestone to jump the whole page to that year.
Recovery is on track, but slow, uneven and climate-dependent
The chlorine and bromine already in the air will take decades to clear. Climate change now matters too. CO₂ cools the upper stratosphere, which slows the chemistry that destroys ozone and so speeds recovery there. It also strengthens the circulation that carries ozone out of the tropics. As a result, outcomes after 2040 depend increasingly on which greenhouse-gas path the world follows.
| Milestone | Expected year | Basis | This site's emulator |
|---|
Near-global ozone under three climate paths
% vs 1964–1980 · after 2025 the selected scenario is drawn heavier
With high CO₂, mid-latitude ozone "super-recovers" above 1980 levels. With low emissions, cleaner air also removes some ozone near the ground, so recovery is slower.
Antarctic hole: the slow fade
Season-mean area, million km² · central projection ± typical weather spread
2026 shows that cold, stable vortex years can still produce large holes, and they remain possible into the 2030s. The trend shows in the decadal average, not in any single year.
The climate story running alongside
The ozone layer and the climate system are tightly linked. CFCs are also powerful greenhouse gases, and their HFC replacements warm the planet too. Rising CO₂ and N₂O reshape stratospheric temperature and chemistry. The ozone hole itself shifted Southern Hemisphere winds for decades.
Carbon dioxide (Mauna Loa)
Annual mean · ppm · NOAA GML · scenarios from IPCC AR6 Annex III (Table AIII.2), anchored to 2025
Global surface temperature
°C above 1850–1900 · NOAA GlobalTemp, scenarios after IPCC AR6
Nitrous oxide: the uncontrolled ozone-depleter
Global mean · ppb · NOAA GML (pre-2001 reconstructed) · scenarios from IPCC AR6 Annex III
N₂O, mostly from fertiliser and manure, is now the largest ozone-depleting emission when weighted by ozone-depletion potential (Ravishankara et al., 2009). It sits outside the Montreal Protocol. Dashed before 2001: reconstructed.
The Montreal Protocol is also a climate treaty
extra warming by 2100 avoided by protecting land plants from UV damage. Healthier plants keep absorbing CO₂ (Young et al., 2021, Nature).
warming avoided by 2100 through the 2016 Kigali Amendment's HFC phase-down (WMO/UNEP 2022).
CO₂-equivalent per year of emissions avoided by 2010 — about 5× the Kyoto Protocol's first-period target (Velders et al., 2007).
cooling of the upper stratosphere since 1979, from rising CO₂ plus ozone loss. This is a fingerprint of human influence: the surface warms while the stratosphere cools.
Southern Hemisphere: from the 1970s to 2000 the ozone hole pushed the westerly jet and storm tracks toward the pole. That shifted rainfall in Australia, South America and the Southern Ocean. As the hole heals, this ozone-driven push is weakening, while greenhouse warming pushes the same way. The two forcings now partly cancel.
What thinner ozone means on the ground
Skin cancer avoided
cases of skin cancer avoided among Americans born up to 2100 thanks to the Montreal Protocol and its amendments. Also about 2.3 million skin-cancer deaths and 63 million cataracts (US EPA / NCAR, 2021).
The "World Avoided"
NASA modelled a world without the treaty. Two-thirds of global ozone would be gone by 2065, a mid-latitude summer UV index near 30 by the 2060s, and ozone holes over the Arctic too. Toggle World Avoided in the bottom bar to see it.
Mid-latitude UV today
Present-day erythemal UV at mid-latitudes compared with the 1964–80 average. Clouds, aerosols and changes in time spent outdoors now matter more than ozone for most people outside the Southern Hemisphere high latitudes.
Southern Ocean life
Reduction in phytoplankton production measured under the ozone hole in the marginal ice zone in spring 1990 (Smith et al., 1992). The effect on the whole ecosystem was small because the hole is seasonal and sea ice offers shade.
Materials and crops
Higher UV-B speeds up the breakdown of plastics, paints and wood, and stresses crops such as soybean and rice. These effects were large in the World Avoided case and are small on the path we are on.
Practical takeaway
Sun protection is still worthwhile whenever the UV index is 3 or more. In southern Chile/Argentina, the Antarctic Peninsula and occasionally New Zealand, spring UV can briefly run far above normal when the ozone hole drifts overhead, as in 2020–2023.
What could speed up, delay or derail recovery
Rogue CFC emissions
From 2012 to 2018, an unreported 7 ± 3 kt/yr of CFC-11 from eastern China slowed the decline. Enforcement cut it back by 2019–2020. Unexplained emissions of CFC-13, CFC-112a, CFC-113a and CFC-115 are still being tracked.
Nitrous oxide
N₂O is rising about 1 ppb per year and is not regulated as an ozone-depleter. In high-emission paths it offsets part of the halogen recovery late in the century.
Solar geoengineering
Injecting sulfate aerosol into the stratosphere to cool the planet would also activate chlorine on particle surfaces. Studies suggest this would delay Antarctic recovery by decades.
Rockets and satellite re-entry
Re-entering satellites leave aluminium-oxide particles in the upper atmosphere. Planned mega-constellations could multiply this many times over. Solid rocket motors emit chlorine and alumina directly into the stratosphere. Both are small today and growing fast.
Volcanoes and wildfire smoke
Pinatubo (1991) cut global ozone by about 2–3% for two years. Australia's 2019–20 fire smoke and the 2022 Hunga Tonga eruption (+~10% stratospheric water vapour) are linked to the large, long-lived holes of 2020–2023.
Very short-lived substances and HFC phase-down
Dichloromethane from industry is growing and is not controlled, a small drag on recovery. The Kigali HFC steps (developed −70% by 2029, −85% by 2036; developing countries to 2045–47) protect climate, not ozone directly.
Where every number comes from
Observations (downloaded 1 Oct 2026)
- Antarctic hole area & minimum, 1979–2025, and 2026 daily values to 29 Sep: NASA Ozone Watch (TOMS/OMI/OMPS, gaps filled from MERRA-2). ozonewatch.gsfc.nasa.gov
- Halley October means, 1956–2020: British Antarctic Survey, J. Shanklin. legacy.bas.ac.uk/met/jds/ozone
- Near-global and Arctic ozone, 1979–2025: NASA SBUV Merged Ozone Data Set v8.7 (MOD v14) zonal means, area-weighted. acd-ext.gsfc.nasa.gov
- EESC & ODGI, 1992–2024: NOAA Global Monitoring Laboratory Ozone Depleting Gas Index. gml.noaa.gov/odgi
- CFC-11, CFC-12: NOAA HATS combined global means, 1978–2025. gml.noaa.gov/hats
- CO₂, N₂O: NOAA GML (Mauna Loa annual means; global N₂O since 2001). gml.noaa.gov/ccgg/trends
- Temperature: NOAA NCEI GlobalTemp, re-baselined to 1850–1900. ncei.noaa.gov
- 2026 season: Copernicus CAMS (16 Sep 2026); BAS situation report (28 Sep 2026). atmosphere.copernicus.eu
- 2025 season: NASA/NOAA, "5th smallest since 1992". science.nasa.gov; WMO wmo.int
Assessments & literature
- WMO/UNEP, Scientific Assessment of Ozone Depletion: 2022: return dates 2040 / 2045 / 2066; Kigali 0.3–0.5 °C. The 2026 Assessment is in preparation. csl.noaa.gov
- Keeble et al. (2021), CMIP6 ozone under SSPs, ACP 21, 5015. acp.copernicus.org
- Newman et al. (2009), "What would have happened to the ozone layer if CFCs had not been regulated?", ACP. NASA summary
- Farman, Gardiner & Shanklin (1985), Nature 315; Molina & Rowland (1974), Nature 249.
- Young et al. (2021), "The Montreal Protocol protects the terrestrial carbon sink", Nature 596.
- Montzka et al. (2018) and Rigby et al. (2019), Nature: unexpected CFC-11 emissions.
- US EPA / NCAR (2021) health benefits study. news.ucar.edu
- Velders et al. (2007), PNAS: Montreal Protocol climate benefit.