Marine Cloud Brightening (MCB)

• Context (TH): Marine cloud brightening (MCB) is a geoengineering technique that produces brighter and whiter low marine clouds.

• Such clouds reflect sunlight away from the ocean’s surface and protect corals from bleaching.

How is a Cloud Brightened?

• A warm cloud (as opposed to an ice cloud) is a collection of small water droplets floating in the air.
• A cloud with numerous small droplets appears brighter than one with fewer large droplets, regardless of their total water content.
• Each droplet is formed by condensation of water vapour around a nucleus.
• The nucleus can be any tiny particle suspended in air.
• In the lower atmosphere, there are thousands of tiny airborne particles called “aerosols”.
• In very clean maritime air, aerosols available are mainly sulphates and sea salt crystals.
• They are generally fewer in number, resulting in the formation of clouds with large droplets.
• So, to boost marine aerosols, large volumes of tiny seawater droplets are sprayed into the air.
• As the tiny seawater droplets evaporate, they leave behind sea salt. These additional sea salts, when incorporated into a cloud, brighten the cloud.

Aerosols can be: Natural such as dust, sea salt, pollen, ash, and sulphates Human-made such as from burning fossil fuels or vegetation, vehicle exhaust, & aerosol spray cans.

Benefits of Marine Cloud Brightening

• Offsets anthropogenic global warming and slows climate change.
• Reduces the risk of extreme weather events (like heat waves and droughts).

Concerns with Marine Cloud Brightening

• Alters precipitation patterns and weather systems.
• Unintended consequences for ecosystems and human health.

For More Information on Coral Bleaching, refer to PMF IAS Environment 2^nd Edition