Montreal Protocol: Ozone Depletion, Vienna Convention, Kigali Amendment on HFCs and India’s Commitments (UPSC Notes + PYQs)

The ozone layer and how it was damaged

About 90% of the atmosphere’s ozone sits in the stratosphere, mostly 15-35 km above the surface. It absorbs most of the Sun’s harmful ultraviolet-B radiation, which causes skin cancer, cataracts and damage to crops and plankton. In 1974 Mario Molina and F. Sherwood Rowland showed that chlorofluorocarbons (CFCs), then used in refrigerators, air conditioners, aerosol sprays and foams, drift up to the stratosphere, where UV light breaks them and releases chlorine. One chlorine atom can destroy thousands of ozone molecules. Bromine from halons (fire extinguishers) and methyl bromide (a fumigant) is even more destructive. In 1985 scientists of the British Antarctic Survey (Joseph Farman, Brian Gardiner and Jonathan Shanklin) reported a deep seasonal fall in ozone over Antarctica: the “ozone hole”. Molina, Rowland and Paul Crutzen shared the 1995 Nobel Prize in Chemistry for this work.

The hole forms over Antarctica in the southern spring (September-October) because winter temperatures there fall below -78°C, forming polar stratospheric clouds. Their ice surfaces turn stable chlorine compounds into active forms, and when sunlight returns, ozone is destroyed rapidly. A strong polar vortex keeps the cold air trapped.

From Vienna to Montreal

The Vienna Convention for the Protection of the Ozone Layer (1985) was a framework: countries agreed to cooperate on research and to take measures, but set no targets. Two years later, on 16 September 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer was signed with binding cuts. It came into force on 1 January 1989. The date of signing is now marked as the International Day for the Preservation of the Ozone Layer. The Protocol was tightened by a series of amendments as the science grew clearer: London (1990), Copenhagen (1992), Montreal (1997), Beijing (1999) and Kigali (2016). In 2009 the Vienna Convention and the Montreal Protocol became the first treaties in UN history to be ratified by every member state.

How the Protocol works

• Controlled substances are listed in annexes: CFCs, halons, carbon tetrachloride, methyl chloroform, methyl bromide, HCFCs and (after Kigali) HFCs.
• Common but differentiated timelines: developing countries (called Article 5 parties) get extra years for each phase-out.
• Multilateral Fund (set up by the London Amendment, 1990) pays the agreed incremental costs of developing countries for switching technology. It is run with UNEP, UNDP, UNIDO and the World Bank as implementing agencies.
• Trade measures: parties may not trade controlled substances with non-parties, which pushed nearly every country to join.
• Licensing of imports and exports, and a non-compliance procedure that helps rather than punishes.
• Regular scientific assessments by expert panels guide the Meeting of the Parties.

The Kigali Amendment and HFCs

CFCs were replaced first by HCFCs, which harm ozone less, and then by hydrofluorocarbons (HFCs), which contain no chlorine and do not harm ozone at all. But HFCs are greenhouse gases thousands of times more potent than carbon dioxide; HFC-134a, a common car AC gas, has a 100-year global warming potential of about 1,430. With air conditioners spreading across hot, growing economies, HFC use was rising fast. At Kigali, Rwanda, in October 2016 the parties agreed to phase down HFCs by 80-85% by the late 2040s. Scientists estimate this can avoid up to about 0.4°C of warming by 2100. The amendment came into force on 1 January 2019.

Countries were put in groups. Developed countries began cutting in 2019. Most developing countries, including China, froze use in 2024. India, with Pakistan, Iran, Iraq and the Gulf states, is in the group with the latest schedule because of hot climates: baseline years 2024-2026, a freeze in 2028, and cuts of 10% (2032), 20% (2037), 30% (2042) and 85% by 2047. The Union Cabinet approved ratification in August 2021.

India and the Protocol

India joined the Montreal Protocol in 1992. The Ozone Cell in the Ministry of Environment, Forest and Climate Change is the national unit that runs the programme, and the Ozone Depleting Substances (Regulation and Control) Rules, 2000 give legal force to licensing and phase-out dates. India phased out the production and use of CFCs, carbon tetrachloride and halons by 1 January 2010, ahead of its schedule for some substances, and phased out HCFC-141b, used in making foams, by 1 January 2020. The HCFC Phase-out Management Plan is being run in stages with support from the Multilateral Fund, retraining refrigeration technicians and converting factories.

India was also among the first countries to prepare a Cooling Action Plan (March 2019). It looks 20 years ahead and aims to reduce cooling demand across sectors by 20-25% and refrigerant demand by 25-30% by 2037-38, train 1 lakh servicing technicians, and promote research on alternative refrigerants. The plan matters because India’s room AC stock is expected to grow several times over as incomes and temperatures rise.

Is the ozone layer healing?

Yes, slowly. The 2022 Scientific Assessment of Ozone Depletion (WMO and UNEP, released January 2023) found that nearly 99% of banned ozone-depleting substances have been phased out. If current policies hold, ozone is expected to return to 1980 values by around 2066 over Antarctica, around 2045 over the Arctic and around 2040 for the rest of the world. Because CFCs are also greenhouse gases, the Protocol has done more to slow warming than any other treaty so far. Threats remain: unexpected CFC-11 emissions traced to eastern China around 2018 (later reduced after enforcement), nitrous oxide, which is not controlled by the Protocol, and ideas such as stratospheric aerosol injection that could affect ozone.

Why it is called the most successful environmental treaty

• Clear science and an identified villain (a few chemicals made by a few firms).
• Substitutes were available, so industry could switch.
• Money and technology through the Multilateral Fund made developing-country participation fair.
• Trade restrictions made staying out costly.
• The treaty could be adjusted quickly as new evidence came in.

Climate negotiations often look to Montreal for lessons, though carbon dioxide is far harder: it comes from almost all economic activity and has no single cheap substitute.

PYQ trend

Prelims 2015 asked directly which agreement deals with phasing out ozone-depleting substances. Kigali and HFCs, the Climate and Clean Air Coalition (2017) and ozone day appear in current-affairs questions. In Mains, use Montreal as a model of successful global cooperation in GS-III climate answers.

Montreal Protocol: UPSC angle

Montreal Protocol UPSC PYQs (Prelims)

Questions UPSC has actually asked, from the official papers. Pick an option to check yourself.

Mains PYQs on this topic

No UPSC Mains question from 2023-2026 is directly on this topic. Older papers (2013-2022) will be added as the Mains bank grows.

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Image: https://commons.wikimedia.org/wiki/File:Ozone_Hole_Over_Antarctica_Reaches_Annual_Maximum_(NESDIS_2015-12-19).png