Montreal Protocol

1. Scientific basis and treaty architecture

Stratospheric ozone, concentrated mainly about 15–35 kilometres above Earth, absorbs most harmful ultraviolet-B radiation and virtually all ultraviolet-C radiation. Ozone depletion increases risks of skin cancer, cataracts and damage to crops, phytoplankton and ecosystems. It must be distinguished from ground-level ozone, which is a harmful secondary pollutant and greenhouse gas. The Montreal Protocol protects stratospheric ozone; it is not a general air-pollution treaty.

Chlorofluorocarbons and several other ozone-depleting substances are sufficiently stable to reach the stratosphere. There, ultraviolet radiation breaks them down, releasing chlorine or bromine that catalytically destroys ozone. Antarctic ozone depletion is especially severe because extreme winter cold permits polar stratospheric clouds to form. Reactions on these clouds activate chlorine, while the polar vortex limits mixing. Returning sunlight triggers rapid ozone destruction in the Antarctic spring.

The 1985 Vienna Convention established a framework for scientific cooperation, monitoring and information exchange. The Montreal Protocol added binding controls on specified chemicals. Its measures became progressively stronger as scientific evidence and alternatives developed. Amendments can add new obligations and require ratification, while the Protocol’s adjustment procedure enables tightening of existing control schedules without a fresh round of ratification by every party.

• Ozone-depletion potential measures a substance’s relative capacity to destroy ozone, conventionally using CFC-11 as the reference.
• Global-warming potential compares the warming effect of a greenhouse gas with carbon dioxide over a specified time horizon, commonly 100 years.

2. Controlled substances and compliance mechanisms

Controlled ozone-depleting substances include CFCs, halons, carbon tetrachloride, methyl chloroform, HCFCs and methyl bromide. They historically served as refrigerants, aerosol propellants, foam-blowing agents, solvents, fire suppressants and fumigants. HCFCs have lower ozone-depletion potential than many CFCs but still damage ozone; therefore, their use as transitional substitutes did not exempt them from eventual phase-out.

The treaty primarily controls calculated production and consumption, rather than directly prescribing an emissions ceiling. Consumption is broadly production plus imports minus exports, with treaty-specific rules governing the calculation. Controls do not automatically prohibit continued operation of every existing appliance. Refrigerant banks in equipment, insulation foams and stockpiles can continue releasing chemicals after new production has been phased out.

Parties report data, establish licensing systems for controlled imports and exports, and follow substance-specific reduction schedules. Restrictions on trade with non-parties discourage free-riding and help prevent relocation of controlled production. Non-compliance procedures combine assistance with the possibility of further measures. Exemptions are narrowly defined: for example, methyl bromide used for quarantine and pre-shipment purposes is exempt from its general phase-out controls.

Article 5 provides qualifying developing countries with differentiated schedules. The Multilateral Fund, established in 1991, finances agreed incremental costs of compliance for eligible developing countries. Its implementing agencies include UNEP, UNDP, UNIDO and the World Bank. This combination of predictable finance, technology support and binding obligations makes the Protocol a major example of operational environmental equity.

3. Kigali Amendment: the climate-governance connection

Replacing CFCs and HCFCs with HFCs solved one environmental problem only partly: HFCs contain neither chlorine nor bromine and do not deplete ozone, but many have high global-warming potentials. The Kigali Amendment therefore added HFCs to the Montreal Protocol’s controls. It provides a phase-down, not a complete phase-out, of their production and consumption, calculated in carbon-dioxide-equivalent terms.

Kigali establishes differentiated schedules for developed countries and two developing-country groups. Most Article 5 parties froze HFC consumption in 2024. India belongs to the later group, alongside countries including Bahrain, Iran, Iraq, Kuwait, Oman, Pakistan, Qatar, Saudi Arabia and the United Arab Emirates. India’s baseline uses average HFC consumption during 2024–2026 plus 65% of its HCFC consumption baseline, expressed in carbon-dioxide-equivalent terms.

India’s freeze begins in 2028, followed by reductions from baseline of 10% in 2032, 20% in 2037, 30% in 2042 and 85% in 2047. These are reductions against the treaty baseline, not promises to cut HFC emissions by the same percentages. Full implementation of Kigali could avoid up to about 0.4°C of warming by 2100, with additional potential gains from energy-efficient cooling.

• Montreal and Kigali obligations are distinct from nationally determined contributions under the Paris Agreement.
• Not all fluorinated gases are covered by Kigali: its controls concern listed HFCs, not every industrial greenhouse gas.

4. India’s implementation and cooling transition

The Ministry of Environment, Forest and Climate Change implements India’s commitments through its Ozone Cell. The Ozone Depleting Substances (Regulation and Control) Rules, 2000, notified under the Environment (Protection) Act, 1986, provide the principal domestic framework for regulating controlled ODS. India completed the phase-out of CFCs, carbon tetrachloride and halons for controlled uses by 1 January 2010, while HCFC elimination follows a longer schedule.

India’s HCFC Phase-out Management Plan supports industrial conversion, technician training and improved servicing practices. Under the Article 5 schedule, HCFC consumption was frozen in 2013 against the average of 2009–2010 levels. Reduction milestones include 35% in 2020 and 67.5% in 2025, followed by 97.5% in 2030, with a limited servicing allowance through 2039.

The India Cooling Action Plan, launched in 2019, connects refrigerant transition with thermal comfort, energy efficiency and skills. Its indicative goals for 2037–2038 include reducing cooling demand across sectors by 20–25%, refrigerant demand by 25–30%, and cooling energy requirements by 25–40%. These are national planning objectives, not Montreal Protocol phase-out percentages.

Alternatives include hydrocarbons such as propane, ammonia, carbon dioxide and suitable low-GWP fluorinated refrigerants. Their suitability depends on application: hydrocarbons can be flammable, ammonia is toxic, and carbon dioxide systems operate at high pressure. Building design, appliance efficiency, safe installation and refrigerant recovery must therefore accompany chemical substitution.

5. Outcomes, remaining challenges and examination relevance

The UNEP–WMO Scientific Assessment of Ozone Depletion: 2022 reported that nearly 99% of banned ozone-depleting substances had been phased out. If current policies remain in place, ozone is expected to return to 1980 values around 2040 for most of the world, around 2045 over the Arctic and around 2066 over Antarctica. These are conditional scientific projections, not fixed treaty deadlines.

Recovery remains gradual because many controlled chemicals persist for decades. Annual ozone-hole size also varies with atmospheric temperature, circulation and other influences; a large ozone hole in a particular year does not by itself prove that the treaty has failed. Illegal production, mislabelled trade and leakage from old equipment remain important challenges.

The Protocol demonstrates the value of scientific assessment, staged obligations, financial support and adaptable rules. However, climate-friendly cooling requires attention to both direct refrigerant emissions and indirect emissions from electricity use. For Prelims, carefully distinguish ozone depletion from global warming, phase-out from phase-down, and treaty commitments from domestic cooling-policy targets.

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