• These agreements are now hailed as the most successful environmental treaties in history, showing what coordinated global action can achieve when science leads and politics listens.

The Montreal Protocol (1987) and the Vienna Convention (1985) led to the phase-out of over 99% of ozone-depleting substances—the silent culprits behind a global crisis. From refrigeration and air conditioning to everyday aerosols, chlorofluorocarbons (CFCs) were once everywhere. Now, they’re nearly gone.

As the world marks the International Day for the Preservation of the Ozone Layer, one truth stands tall: multilateral agreements work. They don’t just promise, they deliver. The Vienna Convention, the Montreal Protocol, and the Kigali Amendment of 2016 weren’t just diplomatic signatures. They were lifelines for a planet in peril.

And the results are visible. According to the World Meteorological Organization’s Ozone Bulletin 2024, released on September 16, 2025, the ozone hole over Antarctica was smaller and slower to form than in recent years, a strong signal of recovery. The ozone layer is healing faster than expected.

These agreements are now hailed as the most successful environmental treaties in history, showing what coordinated global action can achieve when science leads and politics listens.

It all began in 1985, when British researchers discovered a massive ozone hole over Antarctica. The evidence was irrefutable: human-made chemicals were tearing through Earth’s invisible shield, the layer that blocks harmful ultraviolet (UV) radiation. Its depletion triggered global alarm: rising risks of skin cancer, cataracts, and damage to crops, marine life, and ecosystems.

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The Vienna Convention, signed in March 1985, was the diplomatic warm-up act. It committed countries to cooperate in research, share information, and take “appropriate measures” to prevent further harm. The treaty was signed by 28 countries, including Kenya, Canada, the UK, and the US.

But it stopped short of binding chemical limits.

That changed in 1987, when the Montreal Protocol was adopted under the Vienna Convention’s umbrella. This time, the world meant business. The Protocol introduced legally binding targets to phase out ozone-depleting substances like CFCs, halons, and later HCFCs. Countries agreed to specific deadlines, backed by financial and technical support for developing nations. It is now ratified by all UN member states, making it the first treaty in history to achieve universal participation

According to the UN Secretary-General António Guterres, the healing of the ozone layer reminds us that when we heed the warnings of science, progress is possible.

“Yet, we are hurtling towards pushing global temperature rise above 1.5°C. This Ozone Day, let’s recommit to preserving our ozone layer & to protecting people & planet.”

The ozone story is proof that science-led diplomacy can reverse environmental damage and that treaties, when backed by action, can heal even the sky.