Syllabus:

GS-3: Conservation, Environmental Pollution and Degradation, Environmental Impact Assessment.

Context: A recent Earth’s Future study proposed a cost-effective method for stratospheric aerosol injection, potentially advancing the controversial technique.

More on the News

• The new study’s researchers simulated various particle-injection strategies, particularly low-altitude Stratospheric Aerosol Injection (SAI). 
• Using the UK’s Earth System Model 1 (UKESM1), a computer model of the climate, they simulated the “spraying” of sulphur dioxide at different altitudes, latitudes, and seasons.

Key Findings

• The study found that injecting 12 million tonnes of sulphur dioxide annually at 13 km altitude during local spring and summer could cool the planet by 0.6°C.
  This is similar to Mount Pinatubo’s 1991 impact.
  For a 1°C cooling, 21 million tonnes would be needed. 
• Injecting at higher altitudes in the subtropics could achieve the same with just 7.6 million tonnes. 
• This method is more feasible and cost-effective, as it can use modified existing aircraft instead of waiting a decade to develop new high-altitude ones for high-altitude SAI.

Stratospheric Aerosol Injection (SAI)

• It proposed a method of cooling the planet and reducing the impacts of climate change by adding a layer of tiny reflective particles to the high atmosphere.
• The method was inspired by volcanic eruptions, which have been known to have a cooling effect on the planet by spewing aerosols into the air. 
• By reflecting more sunlight away from the earth, SAI aims to create a cooling effect that could help combat rising surface temperatures.

Effectiveness of Stratospheric Aerosol Injection (SAI)

• SAI's effectiveness depends on the material, timing, and location of injection. 
• Injecting particles at higher altitudes is more effective, as they remain in the stratosphere for months or even years. In contrast, lower-altitude particles are often trapped in clouds and washed away by rain.

Risks Associated with SAI

• It can have direct side effects like delayed recovery of the ozone hole and acid rain.
• The cooling effect will also be more pronounced in polar regions rather than in the tropics.
• The cooling could mask warming on the ground and make countries complacent about curtailing emissions.
• SAI affects all countries irrespective of the injecting country, and some of these effects may be harmful.