Solar radiation modification

Solar radiation modification (SRM) (or solar geoengineering) is a group of large-scale approaches to reduce global warming by increasing the amount of sunlight that is reflected away from Earth and back to space. It is not intended to replace efforts to reduce greenhouse gas emissions,^[1] but rather to complement them as a potential way to limit global warming.^[2]^: 1489 SRM is a form of climate engineering or geoengineering.

The most-researched SRM method is stratospheric aerosol injection (SAI), in which small reflective particles would be introduced into the upper atmosphere to reflect sunlight.^[3]^: 350 Other approaches include marine cloud brightening (MCB), which would increase the reflectivity of clouds over the oceans.

Climate models have consistently shown that SRM could reduce global warming and many effects of climate change,^[4]^[5]^[6] including some potential climate tipping points.^[7] However, its effects would vary by region and season, and the resulting climate would differ from one that had not experienced warming. Scientific understanding of these regional effects, including potential environmental risks and side effects, remains limited.^[2]^{: 1491–1492}

SRM also raises complex political, social, and ethical issues. Some worry that its development could reduce the urgency of cutting emissions. Its relatively low direct costs and technical feasibility suggest that it could, in theory, be deployed unilaterally, prompting concerns about international governance. Currently, no comprehensive global framework exists to regulate SRM research or deployment.

Interest in SRM has grown in recent years,^[8] driven by continued global warming and slow progress in emissions reductions. This has led to increased scientific research, policy debate, and public discussion, although SRM remains controversial.

SRM is also known as sunlight reflection methods, solar climate engineering, albedo modification, and solar radiation management.

^ Helwegen, Koen G.; Wieners, Claudia E.; Frank, Jason E.; Dijkstra, Henk A. (15 July 2019). "Complementing CO2 emission reduction by solar radiation management might strongly enhance future welfare". Earth System Dynamics. 10 (3): 453–472. doi:10.5194/esd-10-453-2019. ISSN 2190-4979. even if successful, SRM can not replace but only complement CO2 abatement.
^ ^a ^b Intergovernmental Panel on Climate Change (2021). Climate Change 2021: Mitigation of Climate Change – Working Group III Contribution.
^ Ipcc (9 June 2022). Global Warming of 1.5°C: IPCC Special Report on Impacts of Global Warming of 1.5°C above Pre-industrial Levels in Context of Strengthening Response to Climate Change, Sustainable Development, and Efforts to Eradicate Poverty (1 ed.). Cambridge University Press. doi:10.1017/9781009157940.006. ISBN 978-1-009-15794-0.
^ Cite error: The named reference IPCC_AR6_WGI_SRM was invoked but never defined (see the help page).
^ "One Atmosphere: An Independent Expert Review on Solar Radiation Modification Research and Deployment". UN Environment Programme. 2023. Retrieved 9 March 2024.
^ Cite error: The named reference UNEP_WMO_SAI was invoked but never defined (see the help page).
^ Futerman, Gideon; Adhikari, Mira; Duffey, Alistair; Fan, Yuanchao; Irvine, Peter; Gurevitch, Jessica; Wieners, Claudia (10 October 2023). "The interaction of Solar Radiation Modification and Earth System Tipping Elements". EGUsphere: 1–70. doi:10.5194/egusphere-2023-1753.
^ APRI (11 November 2024). "The justice and governance of solar geoengineering: Charting the path at COP29 and beyond". APRI. Archived from the original on 16 January 2025. Retrieved 13 February 2025. Across several major powers and international forums, the growing momentum in solar geoengineering technologies, assessments, and research and development is raising urgent ethical, justice and human and environmental rights issues that need to be addressed.

[1] Helwegen, Koen G.; Wieners, Claudia E.; Frank, Jason E.; Dijkstra, Henk A. (15 July 2019). "Complementing CO2 emission reduction by solar radiation management might strongly enhance future welfare". Earth System Dynamics. 10 (3): 453–472. doi:10.5194/esd-10-453-2019. ISSN 2190-4979. even if successful, SRM can not replace but only complement CO2 abatement.

[IPCC_AR6_WGIII_SRM-2] Intergovernmental Panel on Climate Change (2021). Climate Change 2021: Mitigation of Climate Change – Working Group III Contribution.

[:13-3] Ipcc (9 June 2022). Global Warming of 1.5°C: IPCC Special Report on Impacts of Global Warming of 1.5°C above Pre-industrial Levels in Context of Strengthening Response to Climate Change, Sustainable Development, and Efforts to Eradicate Poverty (1 ed.). Cambridge University Press. doi:10.1017/9781009157940.006. ISBN 978-1-009-15794-0.

[IPCC_AR6_WGI_SRM-4] Cite error: The named reference IPCC_AR6_WGI_SRM was invoked but never defined (see the help page).

[:0-5] "One Atmosphere: An Independent Expert Review on Solar Radiation Modification Research and Deployment". UN Environment Programme. 2023. Retrieved 9 March 2024.

[UNEP_WMO_SAI-6] Cite error: The named reference UNEP_WMO_SAI was invoked but never defined (see the help page).

[7] Futerman, Gideon; Adhikari, Mira; Duffey, Alistair; Fan, Yuanchao; Irvine, Peter; Gurevitch, Jessica; Wieners, Claudia (10 October 2023). "The interaction of Solar Radiation Modification and Earth System Tipping Elements". EGUsphere: 1–70. doi:10.5194/egusphere-2023-1753.

[8] APRI (11 November 2024). "The justice and governance of solar geoengineering: Charting the path at COP29 and beyond". APRI. Archived from the original on 16 January 2025. Retrieved 13 February 2025. Across several major powers and international forums, the growing momentum in solar geoengineering technologies, assessments, and research and development is raising urgent ethical, justice and human and environmental rights issues that need to be addressed.

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