The challenge
Chemicals such as CFCs, once widely used in air conditioners, refrigerators, aerosol cans and insulation foams, were depleting the ozone layer that shields people from harmful ultraviolet rays, and had opened a hole over Antarctica.
The case
The Montreal Protocol on Substances that Deplete the Ozone Layer was signed in 1987 and entered into force in 1989. It set a phase-out plan for both the production and consumption of ozone-depleting substances, and was later strengthened through a series of amendments and adjustments. With the Vienna Convention, it became the first international environmental treaty to be universally endorsed, by 198 nations. The 2022 assessment by its UN-backed Scientific Assessment Panel confirmed the phase-out of nearly 99% of banned ozone-depleting substances. If current policies remain in place, the ozone layer is expected to recover to 1980 values by around 2066 over the Antarctic, 2045 over the Arctic and 2040 for the rest of the world. The 2016 Kigali Amendment extended the treaty to HFCs, powerful climate-warming gases.
Why it worked
Universally agreed, practical targets and regular scientific reviews let the world phase out nearly all ozone-depleting substances. The scientific assessment found the treaty is also helping avoid about 0.5°C of global warming, because many of these chemicals are also greenhouse gases.
Sources
- World Meteorological Organization (2023). Ozone layer recovery is on track, helping avoid global warming by 0.5°C (press release on the 2022 Scientific Assessment).
- WMO/UNEP (2022). Scientific Assessment of Ozone Depletion: 2022, Executive Summary.
- UNEP Ozone Secretariat. The Montreal Protocol on Substances that Deplete the Ozone Layer.
- UNEP Ozone Secretariat. Ozone and you.
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