Daily Static Quiz Prelims Practice 2027
The Montreal Protocol was adopted in 1987 and came into force in 1989. The year 1985 instead marks the Vienna Convention, the framework treaty for ozone protection; 1992 is the year of the Rio Earth Summit (UNFCCC); and 1997 is the year of the Kyoto Protocol.
- The Kigali Amendment (2016) to the Montreal Protocol aims to phase down hydrofluorocarbons (HFCs).
- HFCs are controlled under the Kigali Amendment because they are major ozone-depleting substances.
Statement 1 is correct — the Kigali Amendment, adopted in Kigali, Rwanda in 2016, set timelines to phase down HFCs. Statement 2 is incorrect — HFCs do NOT deplete ozone; they were introduced as substitutes for CFCs and HCFCs, and are controlled because they are potent greenhouse gases with very high global warming potential, making Kigali a climate measure delivered through an ozone treaty.
Option (b) is incorrect — the ozone hole is actually most pronounced over Antarctica during the southern spring (September–October), while Arctic depletion is weaker and less regular. Options (a), (c), and (d) are all correct — about 90% of ozone lies in the stratosphere, roughly 15–35 km above the surface; ozone thickness is measured in Dobson Units (DU); and UV radiation breaks CFCs apart, releasing chlorine atoms, with a single chlorine atom able to destroy thousands of ozone molecules.
- Assertion (A): The Antarctic ozone hole forms mainly during the southern spring.
- Reason (R): Polar stratospheric clouds formed in the extreme winter cold provide surfaces for reactions that release active chlorine, which destroys ozone once sunlight returns in spring.
Assertion A is correct — the ozone hole peaks in September–October, which is spring in the Southern Hemisphere. Reason R is correct and directly explains A — in the Antarctic winter, Polar Stratospheric Clouds (PSCs) form at temperatures below about −78°C, and reactions on their surfaces convert chlorine into reactive forms; when sunlight returns in spring, this chlorine rapidly destroys ozone, which explains the seasonal timing in A.
- World Ozone Day is observed on 16 September.
- The Montreal Protocol is the first UN treaty to achieve universal ratification.
- The Vienna Convention for the Protection of the Ozone Layer was adopted in 1992.
Statement 1 is correct — 16 September marks the date the Montreal Protocol was signed in 1987. Statement 2 is correct too, since the Montreal Protocol became the first UN treaty ratified by every member state, in 2009. Statement 3 is incorrect — the Vienna Convention was actually adopted in 1985, two years before the Montreal Protocol, not 1992.
