The Montreal Protocol is the first universally ratified UN treaty, credited with reversing ozone layer depletion caused by industrial chemicals.
Key Facts
- Date agreed
- 16 September 1987
- Entry into force
- 1 January 1989
- Ratifying parties
- 198 (197 states + European Union)
- Ozone recovery target (global)
- Return to 1980 levels by 2040
- Ozone recovery target (Antarctica)
- Return to 1980 levels by 2066
- Number of amendments
- 8 (1990–2018)
By the Numbers
Location
Cause → Event → Consequence
Scientific evidence accumulated through the 1970s and 1980s demonstrated that chlorofluorocarbons and other industrial substances were breaking down stratospheric ozone, creating a dangerous hole over Antarctica and increasing ultraviolet radiation reaching Earth's surface, prompting urgent international concern.
On 16 September 1987, nations gathered in Montreal and agreed to the Montreal Protocol on Substances That Deplete the Ozone Layer, an international treaty committing signatories to phase out the production and use of ozone-depleting substances. It entered into force on 1 January 1989 and has since been amended eight times.
With 198 parties ratifying the treaty, it became the first universally ratified agreement in UN history. Ozone-depleting substance production has declined substantially, and the Antarctic ozone hole is slowly recovering, with projections forecasting a return to 1980 ozone levels across most of the world by 2040 and over Antarctica by 2066.
Political Outcome
Universal ratification achieved; phaseout of ozone-depleting substances underway and ozone layer recovery confirmed on trajectory