Nations agree to phase out ozone-depleting chemicals in landmark global treaty

Story: 1987 C.E.  |  Last updated: September 16, 1987

On 16 September 1987 C.E., diplomats from dozens of nations gathered in Montreal and did something that had almost never happened before: they agreed, in writing, to stop producing chemicals that were destroying the sky itself. The Montreal Protocol on Substances That Deplete the Ozone Layer was not just a policy document. It was proof that humanity could recognize a planetary emergency, trust the science behind it, and act together — fast enough to matter.

Key facts about the Montreal Protocol

• Ozone-depleting chemicals: The treaty targeted chlorofluorocarbons (CFCs) and related compounds widely used in refrigerators, aerosols, and foam manufacturing — substances that were quietly destroying the stratospheric ozone layer that shields life on Earth from ultraviolet radiation.
• Global ratification: The Montreal Protocol became the first treaty in United Nations history to achieve universal ratification, eventually signed by 198 parties — 197 states and the European Union — making it the most broadly adopted environmental agreement ever negotiated.
• Ozone layer recovery: Climate projections now indicate the ozone layer will return to its 1980 C.E. levels by approximately 2040 C.E. across much of the world, and by 2066 C.E. over Antarctica, where depletion had been most severe.

The crisis that made the treaty possible

Through the 1970s and early 1980s C.E., scientists watching the atmosphere began to notice something alarming. The ozone layer — a band of gas sitting roughly 15 to 35 kilometers above the Earth’s surface — was thinning. Over Antarctica, a hole was opening each spring that had no precedent in the observational record.

The culprits were CFCs: compounds developed in the 1920s C.E. as apparently safe replacements for toxic refrigerants. They turned out to be extraordinarily stable in the lower atmosphere — which meant that instead of breaking down, they drifted upward into the stratosphere, where ultraviolet light split them apart and released chlorine atoms that devoured ozone molecules with brutal efficiency.

British researchers at the British Antarctic Survey, and separately NASA scientists, published data that made the scale of the problem impossible to ignore. A 1985 C.E. paper in Nature confirmed a 40% drop in ozone over Antarctica during springtime. Within two years, the international community had moved from scientific alarm to binding treaty — a pace rarely seen in global governance before or since.

How the agreement worked

The Montreal Protocol set staged, enforceable limits on CFC production and consumption. Developed nations agreed to freeze output at 1986 C.E. levels and achieve a complete phase-out by 1996 C.E. Developing countries received more time — a recognition that their industrial growth was at an earlier stage — and were given until 2010 C.E. for full phase-out, along with a financial mechanism under Article 10 to help them make the transition.

This tiered approach mattered enormously. It meant the treaty was not simply a rich-world agreement imposed on everyone else. It built in equity, even if imperfectly.

The protocol also established something unusual for its time: a requirement that future decisions be guided by ongoing scientific assessments drawn from global expert communities. Rather than setting rules and walking away, the treaty created a living review process. Scientific Assessment Panels convened in 1989 C.E., 1991 C.E., 1994 C.E., 1998 C.E., and 2002 C.E. — each one informing the next round of policy decisions.

The treaty has been amended and strengthened eight times since 1987 C.E., including the 2016 C.E. Kigali Amendment, which extended the framework to address hydrofluorocarbons (HFCs) — the replacement chemicals that turned out to be potent greenhouse gases even if they posed less risk to the ozone layer itself.

A moment built on many shoulders

The story of the Montreal Protocol is often told as a triumph of Western science and diplomacy. That is partly true. But it was also built on atmospheric data gathered from remote stations on every continent and over every ocean. Researchers from Argentina, Brazil, Japan, and the Soviet Union contributed to the scientific foundation. Negotiators from small island nations — communities facing the most direct consequences of ultraviolet exposure and climate change — pushed hard for stronger commitments.

The financial mechanism, which helped developing nations transition away from ozone-depleting substances without sacrificing refrigeration or industrial capacity, was also an acknowledgment that solutions to shared planetary problems have to be shared ones. Countries in Africa and South Asia that had contributed least to the ozone problem were not simply told to adapt — they were given tools to comply.

Former UN Secretary-General Kofi Annan, who knew something about the difficulty of building international consensus, called it “perhaps the single most successful international agreement to date.”

Lasting impact

The most visible downstream effect of the Montreal Protocol is the ozone layer itself, which is measurably healing. Without the treaty, scientists estimate the ozone hole could have covered the entire planet by mid-century, dramatically increasing rates of skin cancer, cataracts, and crop failure worldwide.

But the protocol’s legacy runs deeper than ozone. It demonstrated that the international community could agree on precautionary action to address an invisible, slow-moving environmental threat before it became irreversible. That model — binding targets, differentiated timelines, scientific review, financial support for developing nations — became the template for every major environmental treaty that followed, including the Paris Agreement on climate change.

The Kigali Amendment, which came into force on 1 January 2019 C.E. and commits participating nations to reducing HFC use by more than 80% over 30 years, extends that model into the era of climate action. As of late 2024 C.E., 160 states and the European Union had ratified it.

Blindspots and limits

The treaty’s success has not been seamless. In 2018 C.E., scientists detected unexpected increases in CFC-11 emissions that were later traced to illegal production in parts of East Asia — a reminder that compliance depends on monitoring and enforcement, not just signatures. The transition chemicals adopted to replace CFCs also brought new problems: HFCs are powerful greenhouse gases, and HCFCs still carry ozone-depleting potential, requiring further rounds of negotiation to address.

The protocol’s tiered structure, while equitable in intent, also meant developing nations continued using damaging substances for longer — and the wealthiest countries had already externalized much of their manufacturing, meaning many of the costs of transition fell on communities with less political leverage. The agreement was a genuine achievement, and it came with trade-offs that are worth holding alongside the celebration.

Read more

For more on this story, see: Wikipedia — Montreal Protocol

For more from Good News for Humankind, see:

• Renewables now make up at least 49% of global power capacity
• Indigenous land rights recognized ahead of COP30: 160 million hectares
• The Good News for Humankind archive on environment

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