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Stratospheric Aerosol Injection (SAI) has a number of risks and uncertainties that if studied, may reveal that SAI is not a viable option in combating climate change.

Summary​

Stratospheric Aerosol Injection (SAI) proposes cooling the Earth by injecting reflective particles into the stratosphere, but carries significant risks across environmental, social, and economic domains. Environmental concerns include ozone layer damage, disrupted climate patterns, ecosystem impacts, and rapid warming if deployment stops suddenly. Social and political challenges involve global governance difficulties and potential inequitable impacts between nations. While often considered cost-effective relative to other climate solutions, estimated costs range from tens to hundreds of billions of dollars annually, with true expenses remaining uncertain until implementation. The combination of these unresolved risks and uncertainties suggests SAI may not ultimately prove viable despite its theoretical potential.

SAI is a geoengineering technique proposed to mitigate global warming by injecting aerosols, such as sulfate aerosols, into the stratosphere. While SAI has the potential to cool the planet, it also comes with significant risks and uncertainties that span environmental, social, political, ethical, and economic dimensions. The risks associated with SAI can be broken down into three categories:

Environmental​

The environmental risks and uncertainties associated with SAI are the most pressing as they could drastically and irreversibly alter the Earth's climate, affecting all life on Earth.

Social and Political​

SAI inherently has a global influence as the dispersion of aerosols within the atmosphere does not obey national borders or diplomatic treaties. Disagreements around when to deploy, how to deploy, and who is responsible for SAI will differ depending on a nations internal perceptions of the benefits of a program 6. The high degree of uncertainties of the regional climate effects of a SAI program may also result in some nations reaping large benefits while other nations remain worse off. An intentional global geoengineering program of this scale has never been attempted before and it is unknown whether the political and diplomatic systems currently in place are capable of coordinating such an effort.

Economic Costs​

SAI is often touted as the most cost effective method for tackling climate change, with some estimates reaching as low into the tens of billions of dollars while others reaching the hundred of billions 7. However, the true cost of a SAI program will never be known until a experimental program reveals the practical challenges that will need to be overcome.

Sources​

Footnotes​

  1. Crutzen, P. J. (2006). Albedo enhancement by stratospheric sulfur injections: A contribution to resolve a policy dilemma? Climatic Change, 77(3-4), 211-220. https://doi.org/10.1007/s10584-006-9101-y ↩

  2. Solomon, K. R. (2008). Effects of ozone depletion and UV-B radiation on humans and the environment. Atmosphere-Ocean, 46(1), 185-202. https://doi.org/10.3137/ao.460109 ↩

  3. Nian, D., Bathiany, S., Ben-Yami, M., Boers, N., Boulton, C., Buerger, M., ... & Scheffer, M. (2023). A potential collapse of the Atlantic Meridional Overturning Circulation may stabilise eastern Amazonian rainforests. Communications Earth & Environment, 4(1), 470. https://doi.org/10.1038/s43247-023-01123-7 ↩

  4. Tracy, S. M., Moch, J. M., Eastham, S. D., & Buonocore, J. J. (2022). Stratospheric aerosol injection may impact global systems and human health outcomes. Elementa: Science of the Anthropocene, 10(1), 00047. https://doi.org/10.1525/elementa.2022.00047 ↩

  5. Williamson, P., & Bodle, R. (2016). Update on climate geoengineering in relation to the Convention on Biological Diversity: Potential impacts and regulatory framework (Technical Series No. 84). Secretariat of the Convention on Biological Diversity. ↩

  6. National Academies of Sciences, Engineering, and Medicine. (2021). Reflecting sunlight: Recommendations for solar geoengineering research and research governance. National Academies Press. https://doi.org/10.17226/25762 ↩

  7. Hulme, M. (2012). Climate engineering through stratospheric aerosol injection. Progress in Physical Geography: Earth and Environment, 36(5), 694-705. https://doi.org/10.1177/0309133312456414 ↩