- Context (TH): Stratospheric Aerosol Injection is feasible, but global risks and ecological concerns remain.
Stratospheric Aerosol Injection (SAI)
- Stratospheric Aerosol Injection is a solar geoengineering technique proposed to combat global warming by artificially cooling the Earth’s surface.
- Ii involves deliberate injection of reflective aerosols, such as sulphur dioxide (SO₂), into the stratosphere, where they reflect a portion of incoming solar radiation back into space.
- This technique mimics the natural cooling effect observed after major volcanic eruptions, offering a short-term strategy to offset rising temperatures caused by greenhouse gas emissions.
Source: The Hindu
-
Cooling Mechanism:
- Chemical Conversion: Injected SO2 reacts with water vapor in the stratosphere forming sulfuric acid aerosols (H₂SO₄). These aerosols do not fall quickly and linger for months to years.
- Radiative Forcing Reduction: The aerosols increase Earth’s albedo (measure of solar energy reflected by Earth). Enhanced albedo leads to reduced solar radiation reaching the Earth’s surface.
- Aerosols, tiny suspended particles, whether natural (like volcanic ash) or anthropogenic (like industrial soot), can alter the Earth’s radiation balance.
- The stratosphere, the stable atmospheric layer above the troposphere (~10–50 km altitude), contains the ozone layer and can host aerosols for longer durations.
- Geoengineering refers to large-scale, deliberate climate interventions, mainly categorized as Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM).
|
Significance of SAI
- Climate Cooling Potential: Injecting 12 million tonnes of SO₂ annually at 13 km altitude could cool Earth by ~0.6°C; 21 million tonnes needed for 1°C cooling (2025 study).
- Aerosol Behaviour: Higher-altitude aerosols stay longer (months to years), enhancing cooling, especially near the equator where the stratosphere is higher.
Challenges
- Environmental Risks: May disrupt monsoon patterns, hydrological cycles, delay ozone recovery (increasing UV and acid rain), and mask global warming, reducing urgency for emission cuts.
- Unequal Climate Effects: More cooling in polar regions than tropics, raising fairness concerns.
- Global Governance Challenges: Aerosol injection affects all nations, creating geopolitical risks amid lacking global regulation.
- Scientific Uncertainties: Cooling requires continuous injection—sudden stop risks rapid warming (“termination shock”).
Learn in depth about > Geoengineering techniques and their ethical desirability.
