IAS 2019 — Environment & Ecology Environment & Ecology

2019mcqmedium

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?

Official previous-year question

Verified 2 Aug 2026.

Options

ACreating the artificial rains in some regions
BReducing the frequency and intensity of tropical cyclones
CReducing the adverse effects of solar wind on the Earth
DReducing the global warming

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Solution

Correct Option (D)

The techniques of cirrus cloud thinning and stratospheric sulphate aerosol injection are proposed geoengineering methods primarily aimed at reducing global warming.

Cirrus Cloud Thinning (CCT) involves modifying high-altitude cirrus clouds to make them less reflective to longwave radiation emitted from Earth. By thinning these clouds, more terrestrial radiation can escape into space, thereby reducing the greenhouse effect and contributing to a cooling effect.
Stratospheric Aerosol Injection (SAI) involves introducing reflective aerosols, such as sulphates, into the stratosphere. These aerosols scatter incoming solar radiation back into space, reducing the amount of sunlight reaching the Earth's surface and leading to a cooling effect. This concept is inspired by the observed temporary global cooling after large volcanic eruptions that inject sulphate aerosols into the stratosphere.

Incorrect Options:

1) Creating artificial rains in some regions: Artificial rain, or cloud seeding, typically involves introducing substances like silver iodide or dry ice into clouds to stimulate precipitation. This process is distinct from cirrus cloud thinning or stratospheric aerosol injection, which target different atmospheric layers and mechanisms for climate modification.
2) Reducing the frequency and intensity of tropical cyclones: While global warming is linked to changes in tropical cyclone patterns, the primary and direct aim of cirrus cloud thinning and stratospheric aerosol injection is not the reduction of cyclone frequency or intensity. Their main objective is to lower global temperatures. Any impact on tropical cyclones would be an indirect consequence of overall climate cooling.
3) Reducing the adverse effects of the solar wind on the Earth: Solar wind consists of charged particles emitted from the Sun, which interact with Earth's magnetosphere. Mitigating the effects of solar wind is a matter of space weather protection and involves technologies like magnetic shielding or understanding space weather phenomena, not atmospheric manipulation techniques such as cirrus cloud thinning or stratospheric aerosol injection. These atmospheric techniques operate within Earth's atmosphere and do not influence extraterrestrial phenomena.

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Correct Option (D)

The techniques of cirrus cloud thinning and stratospheric sulphate aerosol injection are proposed geoengineering methods primarily aimed at reducing global warming.

Cirrus Cloud Thinning (CCT) involves modifying high-altitude cirrus clouds to make them less reflective to longwave radiation emitted from Earth. By thinning these clouds, more terrestrial radiation can escape into space, thereby reducing the greenhouse effect and contributing to a cooling effect.
Stratospheric Aerosol Injection (SAI) involves introducing reflective aerosols, such as sulphates, into the stratosphere. These aerosols scatter incoming solar radiation back into space, reducing the amount of sunlight reaching the Earth's surface and leading to a cooling effect. This concept is inspired by the observed temporary global cooling after large volcanic eruptions that inject sulphate aerosols into the stratosphere.

Incorrect Options:

1) Creating artificial rains in some regions: Artificial rain, or cloud seeding, typically involves introducing substances like silver iodide or dry ice into clouds to stimulate precipitation. This process is distinct from cirrus cloud thinning or stratospheric aerosol injection, which target different atmospheric layers and mechanisms for climate modification.
2) Reducing the frequency and intensity of tropical cyclones: While global warming is linked to changes in tropical cyclone patterns, the primary and direct aim of cirrus cloud thinning and stratospheric aerosol injection is not the reduction of cyclone frequency or intensity. Their main objective is to lower global temperatures. Any impact on tropical cyclones would be an indirect consequence of overall climate cooling.
3) Reducing the adverse effects of the solar wind on the Earth: Solar wind consists of charged particles emitted from the Sun, which interact with Earth's magnetosphere. Mitigating the effects of solar wind is a matter of space weather protection and involves technologies like magnetic shielding or understanding space weather phenomena, not atmospheric manipulation techniques such as cirrus cloud thinning or stratospheric aerosol injection. These atmospheric techniques operate within Earth's atmosphere and do not influence extraterrestrial phenomena.