UPSC Prelims 2019 Q34: Environment & Ecology – Climate Change & Greenhouse Gases
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Methane Hydrate: Facts
| Statement | Claim | Verdict | Detail |
|---|---|---|---|
| 1 | Global warming might release methane from these deposits | TRUE | Warming ocean temperatures and thawing permafrost can destabilize methane hydrates, releasing CH4 - a strong positive feedback (clathrate gun hypothesis). |
| 2 | Deposits found in Arctic Tundra and under seafloor | TRUE | Methane hydrate (methane trapped in ice crystals) occurs in permafrost regions (Arctic tundra) and marine continental margins (~500-2000 m depth). Massive reserves off Japan, Krishna-Godavari basin. |
| 3 | Methane in atmosphere oxidizes to CO2 after a decade or two | TRUE | Atmospheric CH4 has a lifetime of ~12 years; it oxidizes via OH radicals to CO2 and water vapour. That is why methane is short-lived but 84x more potent than CO2 over 20 yrs. |
All three statements are correct. Answer: (d) 1, 2 and 3.
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statement 3 (methane oxidation to CO2 in decades) is also correct.
- (b) Incorrect. Statement 1 (warming-induced release) is also correct.
- (c) Incorrect. Statement 2 (deposit locations) is also correct.
- (d) CORRECT. All three - warming-induced release risk, presence in Arctic and seafloor, and atmospheric oxidation of methane to CO2 in ~12 years - are true.
Key point
Methane hydrate: Ice-like clathrate (CH4 in ice cage) -> Arctic permafrost + marine sediments. Warming can destabilize -> CH4 release. Atmospheric CH4 lifetime ~12 yrs -> oxidizes to CO2.
Remember
All three statements about methane hydrate are correct: global warming can trigger methane release from these deposits (clathrate gun risk), they occur in Arctic tundra permafrost and under the seafloor (marine sediments), and atmospheric methane oxidizes to CO2 after about a decade (its atmospheric lifetime is roughly 12 years).
Common mistakes
- Assuming methane persists indefinitely - it doesn't; ~12 year lifetime.
- Ignoring the 'clathrate gun' feedback risk - a major climate tipping-point concern.
- Not knowing India's KG basin has proven methane hydrate reserves being studied by NGHP (National Gas Hydrate Programme).
Exam tip
GHG lifetimes: CO2 = centuries. CH4 = ~12 years (but 84x GWP over 20 yrs, 28x over 100 yrs). N2O = ~114 years. CFCs = decades to centuries. Short-lived climate pollutants (SLCPs): methane, black carbon, HFCs, tropospheric ozone.
Sources
- IPCC AR6 - Chapter on the carbon cycle and methane hydrates
- Ministry of Petroleum & Natural Gas - National Gas Hydrate Programme (NGHP)