Mentor’s Comment:  The world needs to rely less on fossil fuels, but progress has been slow because of problems like war, poverty, and rising prices. As a result, greenhouse gas emissions are still going up. To deal with this, some scientists suggest using new technologies to cool the Earth directly, instead of only focusing on cutting emissions. One such method is Stratospheric Aerosol Injection (SAI), where tiny particles are sprayed into the upper atmosphere to block sunlight and reduce warming.

Today’s editorial discusses the Stratospheric Aerosol Injection technique, a key topic for GS Paper III (Science, Technology & Environment), highlighting its potential, challenges, and relevance to climate change mitigation efforts.

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Let’s learn!

Why in the News?

A recent study in the journal Earth’s Future shared a new idea that could make SAI cheaper and easier to use, even though many people are still against it.

Why is the spraying of aerosol needed?

• To Reflect Sunlight and Cool the Planet: Aerosols (like sulphur dioxide) reflect some of the sun’s rays back into space, reducing the heat reaching Earth’s surface. Eg: The 1991 Mount Pinatubo eruption released sulphur dioxide, cooling Earth by about 0.5°C for over a year.
• To Temporarily Reduce Global Warming Effects: SAI can lower atmospheric temperatures temporarily, helping to reduce severe climate effects like heatwaves, ice melt, and sea-level rise. Eg: A study showed spraying 12 million tonnes of sulphur dioxide at 13 km altitude could cool the planet by 0.6°C.
• To Buy Time for Emissions Reductions and Climate Adaptation: While long-term solutions like clean energy are built, SAI could provide a temporary buffer against extreme climate impacts. Eg: It could delay serious effects like crop failure or habitat loss, allowing time for sustainable reforms.

Why is low-altitude SAI seen as cost-effective?

• No Need for Specialized Aircraft: Low-altitude SAI can be conducted using existing aircraft, avoiding the high costs of developing planes that fly above 20 km. Eg: Standard jets like the Boeing 777F can reach stratospheric levels in polar regions, making deployment more affordable.
• Technically Less Challenging: Operating at lower altitudes reduces technical complexity, such as extreme temperature and pressure challenges faced at higher elevations. Eg: Modifying existing jets with pressurized tanks is easier than designing new high-altitude aircraft.
• Faster Implementation Timeline: It enables quicker deployment, avoiding the 10-year delay and multi-billion dollar investment needed for high-altitude SAI systems. Eg: Using current infrastructure, SAI programs could begin much earlier to address urgent climate risks.

How does the use of existing aircraft like the Boeing 777F influence the implementation of SAI technology?

• Reduces Deployment Costs: Using existing aircraft avoids the high capital expenditure needed to design and build specialized high-altitude jets. Eg: The Boeing 777F, a widely available cargo aircraft, can be adapted for SAI at lower stratospheric levels, cutting costs significantly.
• Speeds Up Implementation: Existing jets can be modified and deployed faster, enabling earlier testing and potential use of SAI to address urgent climate risks. Eg: Building high-altitude aircraft may take nearly a decade, but using modified commercial planes could allow operations to start much sooner.
• Requires Feasible Technical Modifications: Though not originally built for aerosol spraying, planes like the Boeing 777F can be retrofitted with specialized equipment. Eg: An August 2024 study proposed adding insulated double-walled pressurized tanks to safely carry and release sulphur dioxide.

What are the Risks and Controversies of SAI?

• Environmental and Health Side Effects: SAI could lead to acid rain, delayed ozone recovery, and unknown ecological disruptions due to aerosol particles in the atmosphere. Eg: Sulphur dioxide, commonly proposed for SAI, can form sulphuric acid in the atmosphere, harming ecosystems and human health.
• Uneven Global Effects: SAI’s cooling impact may not be uniform worldwide, potentially benefiting some regions while worsening droughts, rainfall patterns, or crop yields in others. Eg: Cooling could be stronger in polar regions, while tropical areas, which face the worst climate impacts, may not benefit equally.
• Governance and Ethical Concerns: SAI affects the entire planet, raising questions about who decides when, where, and how it’s used. It may lead to geopolitical tensions and misuse. Eg: A single country unilaterally injecting aerosols could trigger international disputes, especially if neighbouring regions suffer unintended consequences.

Way forward: 

• Establish a Global Governance Framework: International collaboration is essential to regulate research, testing, and potential deployment of SAI, ensuring transparency, accountability, and consent from all affected nations.
• Focus on Complementary Climate Strategies: SAI should be treated as a temporary, supplementary tool, not a replacement for emission reduction. Massive investments must continue in renewables, carbon capture, and adaptation strategies. 

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