~99%
of controlled ozone-depleting substances phased out
— WMO/UNEP, 2022
Daily Dose / Oct 5, 2026 / The Ozone Layer
The Mending Sky
Forty years after scientists found a hole in Earth's sunscreen, the ozone layer is slowly healing — the clearest proof we have that a global environmental treaty can actually work.
18.7Mkm²
Average size of the 2025 Antarctic ozone hole (Sept 7–Oct 13) — the 5th smallest since 1992 and about 30% smaller than the 2006 record of 26.6M km². It broke up nearly three weeks earlier than usual.
Source: NASA & NOAA, 2025
Source: NASA & NOAA, 2025
01 · The scale
How thin is thin?
Ozone is measured in Dobson Units. Squeeze the whole column down to sea-level pressure and 300 DU is a layer just 3 mm thick. Below 220 DU, scientists call it a hole.
92Record low, Oct 2006
2025 minimum147
220“Hole” threshold
Typical average · ≈3 mm≈300
← Less ozone · more UVMore ozone →
Total-column ozone over Antarctica, Dobson Units. Scale runs 80–360 DU. Sources: NASA Ozone Watch; NASA/NOAA 2025.
02 · The trend
The hole peaked, then began to shrink
Mean Antarctic ozone-hole area each spring, million km². Weather makes it noisy year to year, but the ceiling is coming down.
Selected years, NASA Ozone Watch (mean area Sept 7–Oct 13). No data for 1995. 2002 and 2019 were unusually warm stratospheric winters, which shrink the hole for reasons unrelated to chlorine.
03 · The fix
One treaty, every country
The 1987 Montreal Protocol phased out CFCs and their cousins. It is the first UN treaty ratified by every nation on Earth.
−⅓
drop in ozone-depleting chemicals over Antarctica since their peak around 2000 — NASA, 2025
198
parties: universal ratification, first reached in 2009 — UNEP Ozone Secretariat
Projected return to 1980 ozone levels
Rest of world
~2040
Arctic
~2045
Antarctic
~2066
Bars show years remaining from 2025. Projections assume current policies hold — WMO/UNEP Scientific Assessment of Ozone Depletion, 2022.
04 · The world avoided Modeled
What 2065 would have looked like without it
NASA scientists simulated a world that never signed. By 2065, two-thirds of the ozone layer would have been gone.
With the ProtocolWithout it (simulated)
Midsummer UV index, mid-latitudes
With
~11
Without
30
Minutes in summer sun to burn
With
15
Without
5
Share of ozone layer lost by 2065
With
~0%
Without
67%
Simulation, not measurement: Newman et al., Atmos. Chem. Phys., 2009 (NASA “World Avoided”). “With” values are typical present-day levels; ozone recovers to ~1980 levels by mid-century.
05 · The stakes Modeled
What the mending is worth
Fewer cancers and a cooler planet — because CFCs are also potent greenhouse gases, and UV damage would have weakened forests' grip on carbon.
443M
skin cancer cases avoided among Americans born 1890–2100
2.3M
skin cancer deaths avoided in the same U.S. population
63M
cataract cases avoided in the same U.S. population
2.5°C
of extra global warming by 2100 averted (1.7°C from the gases themselves)
Health figures: EPA/NCAR/ICF model, ACS Earth & Space Chemistry, 2021. Warming: Young et al., Nature, 2021. The 2016 Kigali Amendment on HFCs could avoid a further 0.3–0.5°C (WMO/UNEP 2022).
Why it matters · What you can do
The repair isn't finished
- Old fridges, freezers and AC units still hold CFCs and HFCs — use certified appliance recycling so the gas is recovered, not vented.
- Ask that AC and heat-pump repairs use leak checks and refrigerant recovery; choose low-GWP refrigerants when you replace equipment.
- The hole is closing, but UV is not gone: check the daily UV index and use shade, hats and sunscreen when it reads 3 or higher.
- Remember the template: clear science, a binding treaty, and industry alternatives turned a planetary threat into a recovery curve.