Context: 

A sufficiently powerful volcanic eruption can spew sulphates and other aerosols into the stratosphere, cooling the air there. 

About Moon Dust Coolers:

• Researchers from the U.S. have proposed that billions of tonnes of dust can be launched from the moon to a point in space where the earth’s and the Sun’s gravitational fields cancel each other out. 
• The dust will thus be ‘parked’ there, casting a shadow on earth and dimming sunlight to offset carbon emissions. 

Solar Radiation Management (SRM)

• Solar Radiation Management (SRM) is a form of climate engineering that would reduce global warming by reflecting the UV-rays of the sun.

• Methods used for SRM:

• • Space Sunshades, using mirrors in space, placing vast satellites at Lagrange Point 1, space parasol, etc.
  • Stratospheric aerosol injection – methods involving the injection of sulphate aerosols into the stratosphere.
  • Marine Cloud Brightening (spraying a fine seawater spray in the air), seeding of high cirrus clouds with heterogeneous ice nuclei.
  • Surface-Based Options like whitening roofs, growing more reflective crops, etc.

Concerns about SRM models:

• Inadequate: Climate models are still woefully inadequate at estimating the precipitation response to solar radiation perturbations at all scales. 
• Uncertain:Any projections related to changes in rainfall, as a result of blocking sunlight, will be highly uncertain.
• Governance: Many natural as well as social scientists have expressed grave concerns about SRM science and governance. 

Guiding Principles by the University of Oxford and the Asilomar Conference:

These include that:

• • those involved must clearly and explicitly report the science and technology of these approaches along with their consequences; 
  • deployment and monitoring, verification, and reporting mechanisms should be democratic and inclusive; and 
  • stakeholders must agree on compensation mechanisms for any harm beforehand.

Conclusion:

• Finally, a major caveat of the aerosol loading approach is that there will be a rebound effect once spraying stops and the aerosols are washed out of the atmosphere. 
• So, when the temporary cooling effect is on, we must still reduce emissions. If we don’t, the cooling effect will end and the heating period will recommence.

                                                                                                                                    News Source: The Hindu