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The Montreal Protocol on Substances that Deplete the Ozone Layer, 1987 is an international environmental agreement designed to protect the stratospheric ozone layer by controlling and ultimately phasing out ozone-depleting substances (ODS).
It was adopted on 16 September 1987 under the Vienna Convention for the Protection of the Ozone Layer, 1985, and entered into force on 1 January 1989.
Key Amendments to the Montreal ProtocolAs scientific understanding and alternative technologies evolved, the Montreal Protocol was amended multiple times to accelerate phase-out timelines and add new controlled substances. The major amendments include:
London Amendment (1990): Accelerated CFC and Halon phase-outs; added Carbon Tetrachloride and Methyl Chloroform; established the Multilateral Fund to assist developing countries.
Copenhagen Amendment (1992): Introduced phase-out schedules for HCFCs, Hydrobromofluorocarbons (HBFCs), and Methyl Bromide.
Montreal Amendment (1997): Implemented a mandatory licensing system for import/export of controlled substances and tightened trade restrictions with non-parties.
Beijing Amendment (1999): Added Bromochloromethane; introduced production controls for HCFCs and stricter trade restrictions.
Kigali Amendment (2016): Added Hydrofluorocarbons (HFCs) to the controlled list to mitigate climate change.
Adopted in Kigali, Rwanda, during the 28th Meeting of the Parties (MOP 28), the Kigali Amendment significantly expanded the scope of the original treaty.
India ratified the Kigali Amendment on 27 September 2021.
1. Background & Purpose
When CFCs and HCFCs were phased out due to their ozone-depleting potential, industries adopted Hydrofluorocarbons (HFCs) as replacements. HFCs are non-ozone-depleting, but they are potent greenhouse gases with Global Warming Potentials (GWPs) hundreds to thousands of times higher than carbon dioxide.
Examples of HFCs:
- R-134a
- R-32
- R-125
- R-143a
- R-404A and R-410A mixtures containing HFCs
The Kigali Amendment legally binds member nations to gradually phase down the production and consumption of HFCs by 80–85% by the late 2040s. Successful implementation aims to prevent up to 0.5 °C of global warming by 2100.
2. Principle of Differentiated Schedules
Recognizing varying economic capacity and technological readiness, signatories are categorized into three phase-down groups under the principle of Common but Differentiated Responsibilities:
| Group | Member Countries | Phase-Down Schedule | Target Reduction |
| Group 1 (Developed) | US, EU nations, Canada, Japan, etc. | Phase-down started in 2019 | Cut HFCs to 15% of baseline by 2036 |
| Group 2 (Developing - Early) | China, Brazil, South Africa, etc. | Freeze in 2024, phase-down starts 2029 | Cut HFCs to 20% of baseline by 2045 |
| Group 3 (Developing - High Ambient Temp) | India, Pakistan, Iran, Saudi Arabia, UAE, etc. | Freeze in 2028, phase-down starts 2032 | Cut HFCs to 15% of baseline by 2047 |
3. Operational Requirements & Exceptions
Annex F Control: HFCs were added as controlled substances under a new Annex F.
HFC-23 Destruction: Parties must mandate the destruction (to the extent practicable) of HFC-23—a potent byproduct created during HCFC-22 production—using approved technologies.
Multilateral Fund Financial Support: Developing nations (Article 5 countries) receive financial and technical assistance via the Multilateral Fund to transition to low-GWP alternatives (e.g., natural refrigerants, hydrofluoroolefins [HFOs]).
| Year | Requirement |
|---|---|
| 2028 | HFC consumption/production frozen at baseline |
| 2032 | 10% reduction |
| 2037 | 20% reduction |
| 2042 | 30% reduction |
| 2047 onwards | 85% reduction → only 15% of baseline remains |