The Montreal Protocol came with a ratchet

Sep 16, 2026 · 2 min read

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On September 16, 1987, delegates in Montreal adopted the treaty now routinely credited with phasing out chlorofluorocarbons. The treaty they signed did not require a phaseout.

For the main group of CFCs, the original protocol froze consumption at 1986 levels, then required a 20 per cent reduction by 1993 and a 50 per cent reduction by 1998. Half the problem could remain.

The document’s more consequential provision was procedural. Article 2 allowed the parties to revise the control schedule as scientific, environmental, technical and economic assessments improved. These decisions were called adjustments. If consensus failed, they could be adopted by a qualified two-thirds vote. Once circulated by the depositary, an adjustment became binding on every party, normally after six months.

That was different from an amendment. Adding newly controlled chemicals or changing the treaty’s machinery required countries to accept a new legal text through their own ratification processes. An adjustment could tighten the timetable for substances already listed without reopening the entire treaty in every capital.

The parties used the distinction. As evidence worsened and substitutes became practical, adjustments agreed in 1990 and 1992 accelerated the CFC schedule. For industrialized countries, the original 50-per-cent target in 1998 became a phaseout by 1996. Later meetings adjusted controls again. The consolidated protocol now contains layers of decisions made in London, Copenhagen, Vienna, Montreal and elsewhere.

This makes the famous agreement slightly harder to describe. Its first controls were not remotely sufficient to produce the result for which it is praised. But the negotiators did not have to choose between a weak permanent bargain and an ambitious bargain that might attract too few countries. They put the initial compromise into force and gave it a way to become less compromising.

The protocol’s strength was not that everyone in Montreal correctly specified the next several decades. It was that they signed a schedule with a ratchet attached.