In the 1970s and 1980s, scientists discovered a hole forming in the stratospheric ozone layer above Antarctica. The cause was chlorofluorocarbons — CFCs — synthetic chemicals used in refrigerants and aerosols. The world's response was the Montreal Protocol of 1987. Nearly every country ratified it. And then, quietly, the ozone layer began to heal.
The Latest Assessment
The 2026 Scientific Assessment of Ozone Depletion, published jointly by the WMO and UNEP, delivers its most encouraging findings yet. Atmospheric concentrations of ozone-depleting substances continue to decline. The Antarctic ozone hole is shrinking on average. In the mid-latitudes of the Northern Hemisphere, ozone levels are recovering measurably.
The assessment projects that global average ozone levels will return to 1980 pre-depletion values by approximately 2066. The Kigali Amendment, adopted in 2016 to phase down HFCs, will also avoid an additional 0.5°C of global warming — turning an ozone protection treaty into a climate action instrument.
Why This Matters
The ozone recovery is one of the few genuine examples of humanity identifying a global environmental crisis, agreeing on a cause, negotiating binding international action, and seeing measurable results.
"The Montreal Protocol is arguably the most successful international environmental agreement in history," said the WMO Secretary-General. "Its success offers a model of what collective action can achieve."
Complete recovery is still 40 years away. But the trajectory is right — because the chemistry was clear, the science was trusted, and governments chose to act. In 1987, phasing out CFCs seemed economically catastrophic. They found alternatives. The sky did not fall. And the sky, slowly, is healing.
Sources: WMO/UNEP Scientific Assessment of Ozone Depletion, 2026; World Meteorological Organization; United Nations Environment Programme; NASA Ozone Watch
