UPSC Prelims 2019 Q25: Environment & Ecology – Climate Change & Greenhouse Gases
- (a) Creating the artificial rains in some regions
- (b) Reducing the frequency and intensity of tropical cyclones
- (c) Reducing the adverse effects of solar wind on the Earth
- (d) Reducing the global warming
Answer: (d) Reducing the global warming
Explanation
Solar Radiation Management: Cirrus Thinning & Sulphate Aerosols
| Technique | Purpose | Mechanism |
|---|---|---|
| Cirrus cloud thinning | Reduce global warming | Cirrus clouds are high-altitude ice clouds that trap outgoing longwave radiation (net warming). Seeding them with ice nuclei thins them and lets heat escape. |
| Stratospheric sulphate aerosol injection (SAI) | Reduce global warming | Sulphate aerosols in the stratosphere reflect incoming solar radiation back to space (mimics volcanic eruption cooling - e.g. Mount Pinatubo 1991 caused ~0.5 C global cooling). |
Both are proposed geoengineering / Solar Radiation Management (SRM) techniques to counter global warming. They are controversial - side-effects include monsoon disruption, ozone impact, termination shock.
Answer: (d) Reducing the global warming.
Why each option is right or wrong
- (a) Incorrect. Artificial rain uses cloud seeding (silver iodide, salt) in tropospheric clouds - not stratospheric aerosols or cirrus thinning.
- (b) Incorrect. Tropical cyclones are not the target - climate cooling (broader global warming) is.
- (c) Incorrect. Solar wind is deflected by Earth's magnetosphere - not by cloud/aerosol techniques.
- (d) CORRECT. Cirrus cloud thinning and stratospheric sulphate aerosol injection are both proposed geoengineering techniques to reduce global warming.
Key point
Cirrus thinning + Stratospheric aerosol injection = geoengineering solutions to global warming. Cirrus thinning = let heat escape. SAI = reflect sunlight (Pinatubo analogy).
Remember
Cirrus cloud thinning and stratospheric sulphate aerosol injection are both proposed geoengineering techniques - specifically Solar Radiation Management (SRM) - to reduce global warming. Both are controversial because they treat symptoms without cutting emissions and carry side-effect risks (monsoon shifts, ozone depletion).
Common mistakes
- Confusing cloud seeding (rain) with cirrus cloud thinning (climate).
- Not knowing IPCC recognizes these as SRM (Solar Radiation Management) options with high risk.
- Assuming volcanic eruptions warm the climate - they cool it (Pinatubo 1991 -> global temp drop of ~0.5 C for 1-2 years).
Exam tip
Geoengineering categories: (i) CDR (Carbon Dioxide Removal): DAC, BECCS, afforestation, ocean fertilization. (ii) SRM (Solar Radiation Management): Stratospheric aerosols, cirrus thinning, marine cloud brightening, space mirrors. IPCC AR6 discusses both with caution.
Sources
- IPCC AR6 - Working Group I (Chapter on climate response and geoengineering)
- Royal Society - Geoengineering the Climate report (2009)