Solar Geoengineering

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Solar Geoengineering

Solar Geoengineering

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Solar Geoengineering, also called solar radiation modification, involves cooling the earth by radiating absorbed sunlight back into space. It is a subset of geoengineering.

Geoengineering means manipulating the earth’s climate to lower its temperature in a bid to counter global warming.

The basic idea behind Solar Geoengineering

The temperature of the earth’s surface rises by absorbing heat energy from the sun (short wave radiation). The warm surface of the earth emits part of this heat back as infrared radiation (long wave radiation). This outgoing radiation heats the atmosphere. At higher altitudes, the heat escapes into outer space without raising the temperature of the earth’s atmosphere.
Greenhouse gases like carbon dioxide make it difficult for infrared radiation to escape the earth’s atmosphere, causing an imbalance between the incoming and outgoing energies. As the total incoming energy exceeds the total outgoing energy, the surface of the earth warms up.
Solar geoengineering aims at increasing the amount of heat radiated back into space using artificial methods. This will, in turn, reduce the temperature of the earth’s surface.

Types of Solar Geoengineering

Currently, the two commonly proposed methods of solar geoengineering are:

Stratospheric aerosol injection
Marine cloud brightening.

Stratospheric aerosol injection

SAI includes spraying large quantities of tiny particles into the earth’s stratosphere to reflect sunlight and keep the earth cooler.
Scientists have proposed using compounds with reflective properties, like sulphur dioxides or finely powdered calcium carbonate, as aerosols.

The concept of SAI is derived from sulphur clouds released during volcanic eruptions. Powerful volcano eruptions emit a sulphur-rich dust cloud that can reach the stratosphere. It has particles that reflect sunlight and cause a cooling effect.

Marine cloud brightening

Marine cloud brightening proposes spraying sea salt into low-lying clouds to increase their brightness and the ability to reflect sunlight.
This could increase the concentration of droplets at the base of a cloud, which in turn will reflect more sunlight before it reaches the surface of the earth
Marine stratocumulus clouds are thought to be the most suitable because of their prevalence, coverage, accessibility, and generally low cloud drop number concentration
MCB also makes the clouds last longer.

Do you know?

Clouds consist of water droplets, and clouds with smaller droplets are more reflective.

Twomey Effect

Twomey Effect is a concept in climate science related to cloud–aerosol interactions.

Explanation

When human-made or natural aerosols (tiny particles like dust, soot, or sea salt) are present in the atmosphere, they act as cloud condensation nuclei (CCN).
More aerosols mean that a larger number of smaller cloud droplets form instead of fewer larger droplets.
These smaller droplets increase the cloud’s reflectivity (albedo) — meaning the cloud reflects more incoming solar radiation back into space.
- The increase in number density increases the optical depth of the cloud, which results in an increase in the cloud albedo making clouds appear whiter.

FAQs

1. What is Solar Geoengineering?

Solar geoengineering (or solar radiation modification) refers to artificial methods of reflecting a portion of sunlight back into space to reduce global temperatures.

2. What are the main techniques of Solar Geoengineering?

The two most widely discussed techniques are:

Stratospheric Aerosol Injection (SAI)
Marine Cloud Brightening (MCB)

3. What is Stratospheric Aerosol Injection (SAI)?

SAI involves spraying reflective particles like sulphur dioxide or calcium carbonate into the stratosphere to reflect sunlight and cool the Earth.

4. What is Marine Cloud Brightening (MCB)?

MCB proposes increasing the reflectivity of marine clouds by spraying sea salt particles into them, making the clouds whiter and longer-lasting.

5. What is the Twomey Effect?

The Twomey Effect describes how more cloud condensation nuclei (like aerosols) create smaller droplets in clouds, increasing their reflectivity and enhancing the cooling effect.

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