Stratospheric Aerosol Injection (SAI)

Prelims – General issues on Environmental ecology, Bio-diversity and Climate Change.

Mains – General Studies-III (Conservation, environmental pollution and degradation, environmental impact assessment)

Why in news?

A recent study published in the journal Earth's Future has explored an innovative approach to SAI, specifically by investigating low-altitude aerosol delivery, aiming to reduce costs and potentially bring it closer to implementation despite opposition.

• Stratospheric Aerosol Injection (SAI) – It involves injecting aerosols (tiny particles) into Earth's stratosphere.
• These aerosols then reflect a portion of incoming sunlight back into space, thereby reducing the amount of solar radiation reaching the Earth's surface and leading to a cooling effect.
• Low-Altitude SAI – Traditionally, SAI envisioned injections at very high altitudes (above 20 km).
• However, the new study investigates the feasibility of spraying particles at lower heights (e.g., 13 km).

Advantages of Low-Altitude Injection

• Technical Feasibility – It is technically less challenging.
• Aircraft Requirements – It does not require specially designed high-altitude aircraft.
• Accessibility and Cost-Effectiveness – This makes the approach potentially more accessible and cost-effective, as existing aircraft (e.g., Boeing 777F) could be modified, though modifications like insulated double-walled pressurized tanks would still be necessary for safe aerosol transport.
• Faster Implementation – Designing and building specialized high-altitude aircraft takes nearly a decade and billions of dollars.
• Modifying existing aircraft is a faster and cheaper alternative.

Risks and Side Effects

• Increased Aerosol Use – Using three times the usual amount of aerosols (as suggested for 1°C cooling at lower altitudes) carries greater risks.
• Direct Side Effects – These include delayed recovery of the ozone layer and acid rain.
• Uneven Cooling – The cooling effect is projected to be more pronounced in Polar Regions than in the tropics, where warming is more severe.
• Masking Climate Change – A significant concern is that the cooling effect could mask the true extent of global warming, potentially leading to complacency among nations regarding the urgency of curtailing greenhouse gas emissions.
• No Reversal of Climate Change – It is crucial to understand that SAI would not reverse climate change; it would only provide a temporary cooling effect. It also would not address other ecological effects of climate change.
• Social and Geopolitical Risks – The global nature of SAI's effects presents immense challenges regarding governance, fairness, and democratic control. The lack of a clear international framework for its implementation and regulation is a major point of contention.
• International Debate – In 2021, the US National Academies of Sciences, Engineering, and Medicine recommended funding solar geoengineering research with a focus on transparency.
• However, in 2022, an international coalition of scholars called for a moratorium on solar geoengineering R&D, arguing that the technology is "ungovernable in a fair, democratic and effective manner."

Reference

The Hindu | Stratospheric Aerosol Injection (SAI)