In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulphate aerosol into stratosphere?

The correct answer is D (Reducing the global warming). Both techniques are proposals for solar radiation management, a branch of geoengineering. Cirrus cloud thinning aims to remove or thin thin, high cirrus clouds so that more outgoing longwave radiation escapes to space. Stratospheric sulphate aerosol injection mimics the cooling effect of volcanic eruptions such as Pinatubo in 1991 by reflecting a small share of incoming sunlight. Both target the symptom, which is excess heat, rather than the cause, which is greenhouse gas concentration.

• A is wrong. Artificial rain comes from cloud seeding with agents like silver iodide, which works in existing clouds near the surface. It is not stratospheric injection.
• B is wrong. Tropical cyclones are governed by sea surface temperature and atmospheric conditions. No such proposal links these techniques to cyclone control.
• C is wrong. The solar wind is a stream of charged particles. Earth's magnetosphere shields us from it, and stratospheric aerosols have no bearing on it.

For Mains GS-3 (Environment and Climate Change), this topic raises governance questions. Side effects such as ozone depletion, altered monsoon rainfall and the moral hazard of delaying emission cuts make these ideas contested, and they are not a substitute for mitigation.

Trap: Candidates confuse cirrus thinning and aerosol injection with cloud seeding (option A) because all three involve clouds or aerosols.