The Risks and Challenges of Stratospheric Aerosol Injection for Climate Mitigation

Stratospheric aerosol injection (SAI) is a proposed geoengineering technique aimed at mitigating global warming by dispersing aerosols into the atmosphere to reflect sunlight. This concept draws inspiration from natural phenomena, such as volcanic eruptions, which temporarily cool the planet by releasing ash and gases. However, scientists caution that the practical implementation of SAI is fraught with significant risks and challenges.

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A team of researchers led by Miranda Hack from Columbia University emphasizes that while computer models suggest potential benefits of SAI, these models often rely on idealized conditions that do not accurately reflect real-world complexities. V. Faye McNeill, an atmospheric chemist, notes that the range of possible outcomes from SAI is broader than previously understood, highlighting the uncertainties involved in its deployment.

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The researchers conducted an analysis of various factors, including deployment strategies, governance, and material supply chains. They concluded that an effective SAI program would require centralized international governance to manage where and how aerosols are released. However, geopolitical realities currently hinder such cooperation, making the ideal governance scenario unlikely.

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The choice of materials for SAI is another critical consideration. While substances like diamond and zircon dust could be effective, their availability may not meet the projected demand for large-scale aerosol deployment. More abundant materials, such as lime and sulfur, face challenges as they tend to clump together at the required submicron sizes, reducing their cooling efficiency. The researchers argue that without addressing these practical limitations, SAI remains a distant possibility.

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The potential side effects of geoengineering techniques, including SAI, extend beyond environmental concerns. Disrupted rainfall patterns could lead to geopolitical tensions, with nations potentially interpreting unilateral SAI efforts as hostile acts. The concept of "geoengineering wars," where countries sabotage or counteract each other's interventions, has emerged as a significant concern in defense discussions.

Interesting Engineering

Currently, there is a notable absence of international regulations governing geoengineering practices. The London Convention and the Convention on Biological Diversity provide limited guidance, leaving a legal grey area that complicates global cooperation. The United States has advocated for transparency and governance standards in geoengineering research, while the European Union remains focused on emission reductions rather than funding such initiatives. In contrast, China has emerged as a leader in geoengineering research, investing heavily in weather modification programs.

Center for European Policy Analysis

As the urgency to address climate change intensifies, the exploration of geoengineering options like SAI is becoming more prevalent. However, experts warn that without robust governance frameworks and international cooperation, the risks associated with SAI could outweigh its potential benefits. A global moratorium on geoengineering deployment until clear regulations are established has been suggested by some scientists and advocacy groups. The path forward requires careful consideration of both the technological possibilities and the geopolitical implications of altering the Earth's atmosphere.

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• “There are a range of things that might happen if you try to do this – and we're arguing that the range of possible outcomes is a lot wider than anybody has appreciated until now,” — V. Faye McNeill, Atmospheric Chemist

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• “These practical limitations, if left unaddressed, push SAI scenarios further away from the idealized scenarios explored in the literature," the researchers write in their paper.” — Miranda Hack, Aerosol Scientist

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• “The true hazard may not be simply rogue deployment but democratic disunity: if leading nations fail to establish coordinated norms, others may shape the rules of planetary alteration.” — Maciej Filip Bukowski, Head of the Energy and Resilience Program at the Casimir Pulaski Foundation.

Center for European Policy Analysis