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?

Answer: (d) Reducing the global warming

Both are solar-radiation / heat-balance geoengineering: sulphate aerosols reflect sunlight back, thinner cirrus lets more heat escape to space.

The idea

Cirrus clouds act like a blanket — they let sunlight in but trap outgoing heat. Thin them and more heat escapes. Sulphate aerosols in the stratosphere copy a big volcanic eruption (Pinatubo 1991 cooled Earth ~0.5 °C).

Sulphate particles sprayed into the stratosphere → reflect sunlight → less heat comes in → Cirrus clouds thinned → more heat escapes to space

Why the others are wrong

(a) Cloud seeding for rain uses silver iodide or salt, not thinning cirrus.

(b) Nothing here targets cyclones; the effect is on the planet’s whole heat balance.

(c) The solar wind is charged particles, stopped by the magnetic field — clouds and aerosols play no part.

The trap

Most clouds cool the Earth, so “thinning clouds to cool it” sounds backwards. High, thin cirrus is the exception — it warms.

Also know

These are called solar radiation management. Other ideas of the same kind: brightening sea clouds with salt spray, and mirrors in space. The risks: rainfall patterns such as the monsoon could change, warming would return quickly if the spraying stopped, and the oceans would still turn more acidic because the carbon dioxide stays in the air.