← Daily Dose The Slow Repair — Daily Dose No. 075
Daily Dose  /  Oct 1, 2026  /  The Ozone Layer

The Slow Repair

The world banned the chemicals eating the ozone layer almost 40 years ago, and the fix is working. The Antarctic hole is now about 30% smaller than its 2006 record. Full repair still takes most of a lifetime, because CFCs stay in the air for decades.

Antarctic ozone back to 1980 levels
~2066

That is the projected date in the WMO/UNEP 2022 Scientific Assessment, almost 80 years after the Montreal Protocol was signed in 1987.

01 · The scale

How thin is a “hole”?

Ozone is measured in Dobson units: the thickness the whole column would have if squeezed to sea-level pressure. 100 DU equals one millimetre. Below 220 DU, scientists call it a hole.

Markers: 92 DU record low (Oct 2006) · 147 DU 2025 low (Oct 6) · 220 DU hole threshold · ≈300 DU global average. Darker = thinner ozone = more UV-B reaching the ground. Global average ≈ 300 DU, about 3 mm of pure ozone. Sources: NASA Ozone Watch; NASA/NOAA 2025.
02 · The trend

Forty-six springs over Antarctica

Average size of the ozone hole each southern spring (Sept 7 to Oct 13), in million km². It grew fast through the 1980s, peaked in 2006, and is now shrinking slowly and unevenly.

No satellite data for 1995. The 2019 dip came from an unusual stratospheric warming that year, not from faster recovery. Source: NASA Ozone Watch annual record, 1979–2025.
03 · The comparison

Bigger than a continent

Average hole area in selected years, compared with Antarctica itself (≈14.2 million km²).

┆ Antarctica ≈ 14.2 M km² · Source: NASA Ozone Watch; NASA/NOAA 2025.
04 · The timeline

When each sky heals

Projected year that total-column ozone returns to its 1980 level, if today's policies hold.

Antarctic recovery is slowest because its cold polar vortex wrings the most ozone out of each atom of chlorine. Source: WMO/UNEP Scientific Assessment of Ozone Depletion, 2022.
05 · The stakes

What the treaty is preventing

These are modeled “avoided” harms: the difference between the world with the Montreal Protocol and the world without it.

443M
skin cancer cases avoided in the United States
EPA / NCAR / ICF · 2020 · modeled, Americans born 1890–2100
2.3M
U.S. skin cancer deaths avoided
EPA / NCAR / ICF · 2020 · modeled
63M
U.S. cataract cases avoided
EPA / NCAR / ICF · 2020 · modeled
2.5°C
extra warming by 2100 avoided: 1.7°C from CFCs as greenhouse gases plus 0.8°C from UV-damaged plants storing less carbon
Young et al., Nature · 2021 · modeled
>99%
of controlled ozone-depleting substances already phased out
WMO/UNEP Assessment · 2022
198
parties. In 2009 it became the first UN treaty ratified by every country.
UNEP Ozone Secretariat
06 · Why it matters

The fix that worked, and the part still left

The ozone layer is the clearest proof that a global treaty can reverse planetary damage. It also shows how long the payback takes.

Retire old cooling gear properly

Old fridges, freezers and AC units can still hold CFCs and HFCs. Use certified recovery when you scrap them. Don't vent them.

Choose low-GWP refrigerants

The 2016 Kigali Amendment is phasing down HFCs. Fully followed, it cuts expected HFC warming by 2100 from 0.3–0.5°C to under 0.1°C.

Keep checking the UV index

The Antarctic hole will reopen every spring for decades. Until ozone recovers, sun protection still matters, especially at high southern latitudes.

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