BPSC 71st CCE Prelims General Studies · Question 149 of 150

Correct — A, 16th September. The day's full name is the International Day for the Preservation of the Ozone Layer, and the date was not picked for convenience: the United Nations General Assembly proclaimed it in 1994, by resolution 49/114, specifically to commemorate the signing on 16 September 1987 of the Montreal Protocol on Substances that Deplete the Ozone Layer. The sequence behind that signature is worth holding as one chain. Scientific confirmation that the ozone layer was thinning pushed governments to build a cooperation mechanism, which took shape as the Vienna Convention for the Protection of the Ozone Layer, adopted and signed by 28 countries on 22 March 1985; that convention is a framework — it commits parties to cooperate and monitor, but sets no binding cuts. The binding instrument is the Montreal Protocol, drafted in September 1987 and in force from 1 January 1989, which controls nearly 100 chemicals — chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform, methyl bromide and the hydrochlorofluorocarbons brought in as transitional substitutes — each group with its own phase-out timetable, and with 'consumption' defined as production plus imports minus exports, less verified destruction. A handful of essential-use exemptions survive where no substitute works, notably metered-dose inhalers for asthma and halon fire-suppression systems in submarines and aircraft. The Protocol has been revised repeatedly: London 1990, Copenhagen 1992, Vienna 1995, Montreal 1997, Beijing 1999, Montreal 2007, Kigali 2016 and Quito 2018. The same date carries a second anniversary that examiners like — on 16 September 2009 the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification. The 2025 observance fell three days after this paper was written, on the theme 'From science to global action', marking forty years since the Vienna Convention; the World Meteorological Organization's assessment is that the ozone layer's recovery is on track and that the ozone treaties additionally help avoid about 0.5 °C of global warming.

• (b)5th June — 5 June is World Environment Day, the United Nations' principal environmental outreach day, run by the UN Environment Programme and observed since the 1970s. It is the strongest distractor precisely because it is the one environment date almost every candidate knows, so a hurried reader picks it by reflex. But its subject is the environment at large — plastics, air pollution, ecosystems — and it has no connection to the ozone layer or to the Montreal Protocol.
• (c)21st April — 21 April is observed in India as National Civil Services Day and has no environmental content at all. What makes it dangerous is that it sits one day away from a date that does: Earth Day is 22 April, first held on 22 April 1970 and now coordinated in more than 193 countries. A candidate who half-remembers 'something environmental in late April' can convert a one-day slip into a lost mark plus the negative marking.
• (d)5th December — 5 December is World Soil Day, endorsed by the Food and Agriculture Organization and the UN General Assembly, and an official international day only since 2014, established under the leadership of the Kingdom of Thailand — which is why its main honour is the King Bhumibol World Soil Day Award. It concerns soil health, degradation and food security: the ground, not the stratosphere.

Ozone is O₃, and about ninety per cent of the Earth's ozone sits in the stratosphere, in a diffuse band roughly 15 to 35 km up, where it absorbs the ultraviolet-B radiation that would otherwise reach the surface and cause skin cancers, cataracts and damage to crops and plankton. Its thickness is reported in Dobson Units, and the Antarctic 'ozone hole' is conventionally the area where the column falls below 220 DU. The damage mechanism is catalytic. Chlorofluorocarbons are chemically inert in the lower atmosphere, which is exactly why they were adopted as refrigerants, aerosol propellants and foam-blowing agents; being inert, they survive long enough to drift into the stratosphere, where short-wave ultraviolet light finally breaks them apart and frees chlorine atoms. Each freed atom destroys ozone and is regenerated, so a single atom cycles through the reaction many times over. Bromine, released from halons and methyl bromide, is more destructive still per atom than chlorine. The hole is Antarctic and seasonal because the winter polar vortex isolates the air and lets polar stratospheric clouds form, whose surfaces convert unreactive reservoir chlorine into forms that attack ozone as soon as the spring sun returns. Two distinctions matter for exams. Stratospheric ozone is protective while ground-level ozone is a harmful secondary pollutant formed in photochemical smog. And the Montreal Protocol addresses ozone depletion, whereas the Kyoto Protocol and the Paris Agreement address climate change — related atmospheric problems, entirely different treaties.

All four options are real observances, so nothing can be eliminated by dismissing it as invented; the question is purely whether you have attached each date to its subject. The reliable method is to anchor the date to an event rather than to a calendar: the Montreal Protocol was signed on 16 September 1987, the General Assembly created the day in 1994 by resolution 49/114 to mark that signature, and the day therefore has to be 16 September. That single link is the discriminating fact, and it also protects you against a differently worded question — one that asks which treaty the day commemorates, or in which year it was proclaimed. Work through the distractors the same way and each becomes a separate fact rather than a guess: 5 June belongs to the environment at large, 5 December to soil, and 21 April to India's civil services. The trap has two layers. The obvious one is 5 June, because it is the environment date candidates meet first and it is genuinely a UN environmental observance, so it feels right to anyone who has not stored the ozone date separately. The subtler one is 21 April, sitting a single day short of Earth Day on 22 April — near-miss dates of this kind are a favourite in state PCS papers, and with +1 for a correct answer and, under this booklet's own instruction 9, −1/3 for a wrong one, a confident wrong guess costs more than leaving the question untouched.

• 16 September is the International Day for the Preservation of the Ozone Layer, proclaimed by the UN General Assembly in 1994 through resolution 49/114 to commemorate the signing of the Montreal Protocol on 16 September 1987. The 2025 observance, three days after this exam, carried the theme 'From science to global action'.
• The Vienna Convention for the Protection of the Ozone Layer was adopted and signed by 28 countries on 22 March 1985 and is only a framework treaty; the binding cuts came with the Montreal Protocol, agreed 16 September 1987 and in force from 1 January 1989, which controls nearly 100 chemicals under annex-wise phase-out timetables.
• On 16 September 2009 the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification — the fact most often used to call the Protocol the most successful environmental agreement ever concluded.
• The Kigali Amendment was agreed at the 28th Meeting of the Parties on 15 October 2016 at Kigali, Rwanda, and phases down hydrofluorocarbons — substitutes that do not deplete ozone at all but are potent greenhouse gases. The published sequence of revisions runs London 1990, Copenhagen 1992, Vienna 1995, Montreal 1997, Beijing 1999, Montreal 2007, Kigali 2016 and Quito 2018 — so Quito comes after Kigali, not before it.
• The HCFC phase-out schedule was introduced in 1992 and accelerated in 2007: developing countries froze consumption in 2015, with complete phase-out due by 2030 in developed countries and 2040 in developing ones. Essential-use exemptions remain for metered-dose asthma inhalers and for halon fire-suppression in submarines and aircraft.

• Answering 5 June because it is the environment date everyone knows — World Environment Day is about the environment generally and has nothing to do with the ozone layer
• Confusing 21 April with 22 April, which is Earth Day; near-miss dates one day apart are a standing feature of state PCS papers
• Mixing up the treaties — the Montreal Protocol is about ozone-depleting substances, while the Kyoto Protocol and Paris Agreement are climate instruments, and the Kigali Amendment is the bridge between the two

BPSC asks observance dates as bare one-line recall, four dates and one mark, so the efficient revision unit is a single date-to-subject table for the whole environmental calendar rather than any deeper reading. UPSC has asked the same fact, but wrapped: in 2001 it appeared inside a matching set pairing four important days with four dates, and in its modern form UPSC drops the date entirely and tests the substance instead — which agreement controls ozone-depleting substances (2015), or why the hole forms over Antarctica (2011).

• practice — not a real PYQ

  The Montreal Protocol on Substances that Deplete the Ozone Layer entered into force in which year ?

  • (a)1985
  • (b)1987
  • (c)1989
  • (d)1994

  Answer(c) 1989 — the Protocol was signed on 16 September 1987 and entered into force on 1 January 1989. 1985 is the year of the Vienna Convention, and 1994 is the year the General Assembly proclaimed the International Day for the Preservation of the Ozone Layer.

• practice — not a real PYQ

  The Kigali Amendment, adopted in 2016, added which group of substances to the control regime of the Montreal Protocol ?

  • (a)Chlorofluorocarbons (CFCs)
  • (b)Hydrochlorofluorocarbons (HCFCs)
  • (c)Hydrofluorocarbons (HFCs)
  • (d)Halons

  Answer(c) Hydrofluorocarbons (HFCs) — agreed at the 28th Meeting of the Parties at Kigali, Rwanda on 15 October 2016. HFCs do not deplete ozone at all; they were brought in because they are potent greenhouse gases and had been adopted as substitutes for CFCs and HCFCs, both of which the Protocol already controlled.