Why the Montreal Protocol won ratification from all 198 parties
Agreed on 16 September 1987, the Montreal Protocol set out to phase out the chemicals eating away at the ozone layer. Every one of its 198 parties, 197 states plus the European Union, has ratified it, and the Antarctic ozone hole is now slowly healing, expected to recover by around 2066.
The treaty took force on 1 January 1989 and has been revised repeatedly, in London, Copenhagen, Beijing, Kigali and elsewhere. It sets timetables for groups of ozone-depleting substances, requires data reporting and deals with countries that fall short. Under Article 5, developing nations get extra time, and Article 10 created a fund to help them comply. Kofi Annan called it perhaps the single most successful international agreement so far.
For wealthy countries, the main CFCs were frozen at 1986 levels in July 1989 and eliminated by 1996; developing countries finished the job in 2010. Halons followed a similar path. A few essential uses escaped at first, including asthma inhalers and halon fire suppression in submarines and aircraft. Expert panels on science, environment, technology and economics feed their assessments into every decision.
CFCs were first replaced by HCFCs, which break down mostly in the lower atmosphere and do far less harm to ozone, with depletion potentials of 0.01 to 0.5 against 0.6 to 1.0 for CFCs. They are still potent greenhouse gases, so they too are being phased out, with developing countries due to finish by 2030. Their successors, HFCs, contain no chlorine and spare the ozone layer entirely, but they trap heat about as strongly.
That led to the Kigali Amendment, adopted in October 2016 after seven years of talks that began with a proposal from the Federated States of Micronesia. Sweden's ratification in November 2017 pushed it past the threshold, and it took force on 1 January 2019, committing parties to cut HFC use by at least 85 percent. A 2009 study estimated a fast phasedown could avoid up to 0.5C of warming by 2100. By late 2024, 160 states and the EU had ratified it.
Source: Montreal Protocol
