Climate change & agreements

Answer: (c) Only three

Hydrofluorocarbons (HFCs) replaced ozone-depleting CFCs and HCFCs in cooling, aerosol propellants, foam blowing and fire suppression. Lubricants are not an HFC application, so three of the four are correct.

• ✓ 1. HFCs serve as propellants in aerosol cans, one of the uses listed by the US EPA and UNEP.
• ✓ 2. HFCs are used as blowing agents to make insulating and other foams.
• ✓ 3. Some HFCs are used as fire-suppression (fire-extinguishing) agents, a replacement for ozone-depleting halons.
• ✗ 4. Lubricants are oils and greases; HFCs are gases used as refrigerants, propellants, blowing agents and fire suppressants, not as lubricants.

Remember · HFCs: refrigerants, AC, aerosols, foam blowing, fire suppression, solvents. Not ozone-depleting but potent greenhouse gases; phased down under the Kigali Amendment (2016).

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I

Carbon markets put a price on each tonne of emissions and are spreading fast, from the EU's emissions trading system to India's Carbon Credit Trading Scheme (2023). When governments auction emission allowances, money does flow from companies to the State, but that revenue is a by-product; markets are popular because pricing carbon makes polluters cut emissions where it is cheapest.

• ✓ Statement-I Emissions trading and carbon-credit markets are among the most widely adopted climate policy tools; India notified its own Carbon Credit Trading Scheme in June 2023 to put a price on a tonne of CO2-equivalent.
• ✓ Statement-II Where allowances are auctioned, companies pay the government: EU ETS auctions raise revenue for national budgets and climate funds. This transfer is not why carbon markets are used, so Statement-II does not explain Statement-I.

Remember · Carbon market = cap (or intensity target) + tradable permits/credits → carbon gets a price. Auctioned permits raise public revenue. India: Carbon Credit Trading Scheme, 2023 (BEE administers).

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) All three

All three activities are discussed as ways to capture and lock away carbon dioxide. Spreading crushed basalt (enhanced weathering) and adding lime to the sea (ocean alkalinity enhancement) are carbon-removal options assessed by the IPCC, and abandoned mines are listed among niche sites for underground CO2 storage.

• ✓ 1. Enhanced weathering spreads crushed silicate rock such as basalt on soil so that it reacts with atmospheric CO2. The IPCC cites estimates that spreading basalt on farmland in 12 countries could remove up to 2 GtCO2 a year by 2050.
• ✓ 2. Ocean alkalinity enhancement adds alkaline material such as lime to the sea so that it takes up and stores more CO2. The IPCC notes this idea goes back to a 1995 proposal to dissolve highly reactive lime in surface ocean water.
• ✓ 3. The IPCC's report on CO2 capture and storage names abandoned mines, along with basalts and salt caverns, as niche options for geological storage of captured CO2.

Remember · Enhanced weathering (crushed basalt on land), ocean alkalinity enhancement (lime in the sea) and storing captured CO2 underground, even in abandoned mines, are all discussed for carbon removal.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) All three

All three. Green hydrogen, made by splitting water with renewable electricity, can replace the fossil-based hydrogen that fertilizer plants and refineries use today and the coal and coke that steel plants use for reducing iron ore. The Government of India names all three sectors in its National Green Hydrogen Mission.

• ✓ 1. Ammonia for nitrogenous fertilizers is made from hydrogen obtained from natural gas. Green hydrogen, or green ammonia made from it, can replace that and cut gas imports.
• ✓ 2. Refineries already use large amounts of hydrogen made from fossil fuels; swapping it for green hydrogen lowers a refinery's carbon footprint.
• ✓ 3. Hydrogen can replace coal and coke in iron and steel production, one of the biggest carbon-emitting industries; the Mission funds pilot projects for low-carbon steel.

Remember · Green hydrogen targets hard-to-abate sectors: fertilizer (green ammonia), refining, steel, and long-haul transport and shipping. India's mission aims at 5 MMT a year by 2030.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error