A new study published in ‘Earth’s Future’ explores a cost-effective approach to Stratospheric Aerosol Injection (SAI), a form of solar geoengineering aimed at cooling the Earth.
About Stratospheric Aerosol Injection (SAI)
- SAI is a geoengineering technique that involves injecting reflective particles (like sulphur dioxide) into the stratosphere to reflect sunlight and cool the planet.
- It mimics the natural cooling effect observed after major volcanic eruptions like Mount Pinatubo in 1991.
- Currently, it is intended as a climate intervention strategy to temporarily reduce global warming.
Key Findings of the Recent Study Regarding SAI
- Low-Altitude Injection: Injecting aerosols at 13 km using modified existing aircraft is technically possible and less costly than high-altitude methods.
- Cooling Potential Quantified: Spraying 12 million tonnes of sulphur dioxide annually at 13 km can cool the Earth by around 0.6°C.
- Cooling and Aerosol: To achieve 1°C cooling at lower altitudes, 21 million tonnes/year is needed, nearly three times the amount required at higher altitudes. Thereby, greater cooling requires greater aerosol.
- High-Altitude Injection: Injecting at higher subtropical altitudes needs only 7.6 million tonnes/year for the same cooling effect and is more effective, due to longer particle residence time.
- Polar Regions: Cooling effect is stronger in polar regions, while tropical areas,where warming is worse, have seen less benefit.
- Faster Deployment Possible: Using existing aircraft enables earlier deployment compared to waiting for custom high-altitude aircraft, which could take a decade to build.
Global Views on SAI Governance
- 2021: US National Academies advised funding SAI research with transparency.
- 2022: Global scholar coalition called for moratorium, citing SAI as “ungovernable” and democratically unmanageable.
- Intergovernmental Panel on Climate Change (IPCC) cautions against reliance on SAI and promotes mitigation and adaptation instead.
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Risks Related To the Deployment of SAI
- Environmental Risks:
- Acid Rain: Increased sulphur use may lead to acidification of ecosystems.
- Ozone Layer Damage: Deployment of SAI could delay recovery of the ozone layer by enhancing chemical reactions that destroy ozone.
- Uneven Climate Effects: Cooling is more pronounced in polar regions, leaving tropical zones more vulnerable.
- Social and Geopolitical Concerns:
- Unilateral Action: No global regulatory framework currently exists. If a single country deploys SAI, it can alter global climate patterns, raising ethical and sovereignty issues.
- Conflict Risk: SAI may trigger international disputes and strain global climate governance frameworks.
Conclusion
Further studies with wider simulations are essential to assess long-term impacts. However, SAI must not replace emission cuts and global rules are needed to avoid misuse and conflicts.
Aerosols
- Aerosols are suspensions of tiny solid particles or liquid droplets in a gas, usually in the air.
- They can be natural or anthropogenic (human-generated).
- They significantly influence climate, weather, air quality, and even human health.
Types of Aerosols
1. Primary Aerosols:
- Directly emitted into the atmosphere.
- Examples: Sea spray, Mineral dust, Volcanic ash and Smoke from combustion, etc.
2. Secondary Aerosols:
- Formed within the atmosphere via chemical reactions involving precursor gases.
- Examples:
- Sulfate aerosols from volcanic or industrial SO₂
- Nitrate aerosols from NOx emissions
3. Biological Aerosols (Bioaerosols):
- Composed of airborne biological particles.
- Examples: Viruses, Bacteria, Fungal spores and Pollen, etc.
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