Context
- Climate crisis deepens: Global greenhouse gas emissions are rising; mitigation efforts are inconsistent.
- Technological fix: Stratospheric Aerosol Injection (SAI) proposed as a geoengineering method to cool the planet.
- Controversial nature: Global side-effects, ethical concerns, and governance challenges make SAI a divisive topic.
Relevance : GS 3(Technology, Disaster Management )
What is Stratospheric Aerosol Injection (SAI)?
- Method: Injecting tiny reflective aerosols (e.g., sulphur dioxide) into the stratosphere (~20 km altitude) to reflect sunlight and cool Earth.
- Inspired by volcanoes: Mimics natural aerosol emissions from volcanic eruptions like Mount Pinatubo (1991) which cooled Earth temporarily.
- Objective: Directly reduce solar radiation reaching Earth’s surface to offset global warming.
Key Innovation in the New Study
- New approach: Use of existing aircraft (like modified Boeing 777F) to inject aerosols at lower altitudes (~13 km) in polar and extratropical regions.
- Advantage:
- Lower technical barriers
- Cheaper and faster to implement
- Avoids the need for specially designed high-altitude aircraft
Modeling Results
- Climate simulation tool used: UK Earth System Model 1 (UKESM1)
- Findings:
- Injecting 12 million tonnes of SO₂/year at 13 km in spring/summer of both hemispheres may cool Earth by 0.6°C.
- To cool by 1°C, need 21 million tonnes annually at 13 km.
- More efficient: Only 7.6 million tonnes needed if injected higher in subtropics.
Risks and Challenges
- Scientific risks:
- Ozone depletion, acid rain
- Delayed recovery of ozone hole
- Uneven cooling (polar > tropical regions)
- Social and geopolitical concerns:
- Potential misuse or unilateral deployment
- Could divert attention from emissions reductions
- Global impact: One country’s action affects all
- Governance dilemma:
- No global framework exists to regulate such interventions
- 2022: Scholars called for moratorium on solar geoengineering R&D citing fairness and control issues
Is It a Solution?
- Temporary measure only – Cannot reverse root causes of climate change
- Could create “moral hazard” – Mask warming and reduce urgency to cut emissions
- Needs more transparent global dialogue, public accountability, and regulation
