Montreal Protocol

The Montreal Protocol's full name is the Montreal Protocol on Substances that Deplete the Ozone Layer. It is a multilateral environmental agreement designed to protect stratospheric ozone, which absorbs much of the Sun's harmful ultraviolet radiation. The treaty controls the production and consumption of nearly 100 human-made ozone-depleting substances, including chlorofluorocarbons (CFCs) and halons. Its control measures use staged reduction and phase-out schedules rather than a single deadline. Developed and developing countries have different timetables, but both have binding, measurable commitments. Parties also undertake measures such as reporting data and controlling international trade in regulated substances.

The treaty is governed by meetings of its parties, which consider implementation and can adjust or amend its provisions in response to scientific, technical and economic developments. The Multilateral Fund was established in 1991 under the Protocol to provide financial and technical assistance to eligible developing-country parties. This support helps countries meet control schedules and make practical changes in industries that use regulated chemicals. The arrangements combine common environmental goals with different timetables and assistance for countries with differing capacities.

The Protocol has been revised as circumstances changed. One important later development was the Kigali Amendment, agreed in 2016, which added a phasedown of hydrofluorocarbons (HFCs). HFCs were introduced as alternatives to some ozone-depleting substances and do not themselves deplete the ozone layer, but many are powerful greenhouse gases. The Kigali measures therefore extend the treaty's work to reducing the climate impact of these substitutes while maintaining the distinction between ozone-depleting chemicals and climate-warming HFCs.

The Protocol is widely regarded as a major example of international cooperation on an environmental problem. Official assessments link the treaty's control measures with declining emissions of ozone-depleting substances and a recovery trajectory for the ozone layer. A UN-backed scientific assessment reported in 2023 that the ozone layer was on track to recover over the following decades. Continued implementation remains important to sustain that progress. The treaty's history also illustrates how international agreements can be adjusted as new evidence and replacement technologies create new challenges.