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Draft Position Statement on Climate Intervention

This position statement is currently under revision by a writing panel of experts from AGU’s community as part of a recurring four-year review process to reflect current research and understanding of the issue. The community comment period for this position statement ran from 5 December to 20 January 2023 and is now closed. The expert writing panel will now work to incorporate the community’s views to finalize the draft and ensure that the science is reflected accurately. The draft statement will then go for review before the AGU Position Statement Committee, Council and Board.

Statement Draft

The Urgent Priority of a Healthy Climate Requires Enhanced Climate Intervention Research and Community Engagement

Climate intervention (CI) measures cannot substitute for deep cuts in emissions or the need for adaptation. Given the likelihood that the world will overshoot global average temperature targets, climate intervention strategies may be a necessary part of a comprehensive risk-management strategy. Research aimed at understanding the benefits and impacts of climate intervention measures must consider global transparency, ethical and inclusion practices and be subject to robust governance and oversight structures. CI research must be part of a broader climate solutions package, that, given the urgency of addressing climate change, should be funded at a level matching the enormous scale of the space programs of an earlier era.

The Urgency of Action

Human activities are changing the Earth’s climate in ways that have and will continue to cause increasingly disruptive societal and ecological impacts as well as human suffering.[i] Deep reductions in greenhouse gas emissions must be central to any policy response to the dangers of climate change. The likelihood that global average temperatures will overshoot the targets agreed to by the world’s nations (1.5 -2.0 degrees C) has led the Intergovernmental Panel on Climate Change (IPCC) to assess Climate Intervention (CI) as a potential pathway to reduce, remove or offset some of the effects of climate change.[ii]

With CI approaches beginning to proliferate among researchers and diverse funding sources globally, substantial research and evaluation programs are urgently needed to determine the effectiveness, risks, and opportunities of CI and inform societal decisions about possible implementation. It is imperative that the research community and policymakers consider and address the ethical implications of CI globally and fully engage communities in the decision process.[iii] Finally, there is a need for effective and inclusive national and global governance structures that can manage all these considerations.

Climate Intervention Approaches

Climate intervention (CI) is a “deliberate intervention in the planetary environment of a nature and scale intended to counteract anthropogenic climate change and its impacts. “[iv] Such approaches can be large in scale or take the form of cumulative local interventions. The most plausible approaches to CI fall into two distinct categories: carbon dioxide removal (CDR), and solar radiation modification or sunlight reflection method (SRM).

CDR, which involves the removal and storage of atmospheric carbon dioxide, includes both terrestrial and ocean-based approaches, such as large-scale afforestation, direct air capture, and direct ocean capture, among others.[v] These could be deployed at a range of scales and currently vary widely in their scientific and market readiness. SRM, which involves a deliberate alteration to the Earth’s surface or atmosphere, has mostly focused on considering the addition of reflective particles into the upper atmosphere or seeding clouds in the lower atmosphere.[vi] Localized surface albedo modification, while less studied, may also be included in this category. A third category of CI, methane removal, is generally at an earlier stage of scientific and market readiness.

Opportunities & Challenges

Climate intervention approaches cannot replace the urgent need for reductions in greenhouse gas (GHG) emissions or measures to adapt to climate change. Even stopping GHG emissions now could leave Earth at levels of warming many would consider unacceptable.[vii] CI measures could reduce some of the climate driven harms as societies decarbonize. Some CI approaches could cool the climate quickly, which could prove valuable as climate change accelerates and causes increasingly unacceptable damage to lives, property, and ecosystems.

Legitimate concerns exist about the scalability and side effects of some CI approaches, but such concerns do not negate the present need for research, which would shed light on the impacts of and ultimately inform decisions about any possible deployment.

Needed Actions

AGU recommends national funding agencies create substantial CI research including CDR and SRM research programs. Such programs should be embedded, where possible, in existing larger programs on climate science to ensure that the knowledge gleaned will improve understanding of the changing climate system. CI research should be interdisciplinary and integrated into efforts to understand socioeconomic and environmental tradeoffs, ethical and environmental justice considerations, and governance structures and needs. Funding from the philanthropic, public, and private sectors is essential to ensure an adequate level of research support. Regardless of funding source, all CI research must be transparent and adhere to ethical principles such as those that could be included in a research code of conduct.

While much can be learned from laboratory and modeling research, robust CDR and SRM research programs require controlled field experiments. Decisions about where and how to conduct such experiments should be made with the participation of all potentially affected and interested stakeholders, with particular attention to Indigenous Peoples. Each technique will have unique issues that involve different norms of transparency, peer review or intellectual property ownership, and there may be overlap between large-scale experiments and small-scale deployments. All work should be pursued transparently, and include an assessment of biological and environmental risk, safety, and robust engagement.

A proper and full evaluation of potential uses and impacts of CI measures will require a broader dialogue that includes and engages communities and the broader public around the globe. Those proposing CI measures must, with transparency and self-scrutiny, seek to disseminate information widely and facilitate the development of appropriate national and international norms about testing and evaluation of CI systems. Such norms should also include the development of and adherence to a transparent ethical and governance framework to advance safe, fair, inclusive, and equitable action.

Finally, oversight of CI research will be necessary to avoid long-term social and environmental impacts and earn social acceptance. In most countries, adequate governance frameworks do not yet exist. AGU recommends that governments and international governance bodies adopt governance frameworks prior to large scale field experimentation for CDR and SRM. These frameworks should include standard elements of scientific integrity and account for equity by including robust community and public consultation requirements and considering the current differentiated and future equitable distribution of impacts and benefits.



[i] Society Must Address the Growing Climate Crisis Now, AGU, November 2019.

[ii] IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.

IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. World Meteorological Organization, Geneva, Switzerland, 32 pp.

[iii] AGU Climate Intervention Engagement: Leading the Development of an Ethical Framework, AGU, June 2022.

[iv] Secretariat of the Convention on Biological Diversity (2012). Geoengineering in Relation to the Convention on Biological Diversity: Technical and Regulatory Matters, Montreal, Technical Series No. 66, 152 pages.(2012).

[v] National Academies of Sciences, Engineering, and Medicine 2021. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. https://doi.org/10.17226/26278.

[vi] National Academies of Sciences, Engineering, and Medicine 2021. Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance. Washington, DC: The National Academies Press. https://doi.org/10.17226/25762. National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. https://doi.org/10.17226/18988.

[vii] S. Solomon, et. al, Irreversible climate change due to carbon dioxide emissions. PNAS 106 (6) 1704-1709. (2009). https://doi.org/10.1073/pnas.0812721106. Sigmond, M., Fyfe, J.C., Saenko, O.A. et al. Ongoing AMOC and related sea-level and temperature changes after achieving the Paris targets. Nat. Clim. Chang. 10, 672–677. (2020). https://doi.org/10.1038/s41558-020-0786-0. Is there warming in the pipeline? A multimodel analysis of the Zero Emissions Commitment from CO2. Biogeosciences, 17, 2987–3016. (2020). https://doi.org/10.5194/bg-17-2987-2020

Current Statement

Climate Intervention Requires Enhanced Research, Consideration of Societal and Environmental Impacts, and Policy Development

Humans are responsible, through the release of carbon dioxide (CO2) and other greenhouse pollutants, for most of the increase in global average temperatures over the past half century. Deep reductions in these emissions must be central to any policy response to the dangers of climate change. In tandem with those reductions, there may be a need for climate interventions to help reduce or offset some of the effects of climate change. AGU urges national funding agencies to create substantial research programs on climate intervention so that the risks and opportunities are much better understood. A proper and full evaluation of potential uses and impacts of climate intervention will require a broader dialogue that engages more societies and the public.

In conjunction with this statement, AGU has issued a short white paper that examines the case for climate intervention and related research in more detail.i

Climate intervention is a “deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change.”ii The most plausible approaches to climate intervention fall into two distinct categories.

The first category, known as carbon dioxide removal (CDR), utilizes approaches and techniques that remove CO2 directly from the atmosphere. CDR approaches include large-scale afforestation, which is already being done on the planet to some degree, along with enhanced mineralization or weathering, combining energy crops with storage of CO2 in the soils or reservoirs deep underground, and machines that chemically capture carbon dioxide from the atmosphere.

AGU endorses calls for substantial CDR research programs such as those outlined by the National Academies.iii Understanding the economic, environmental, and practical challenges in scaling these options is essential given the urgency of the climate problem and the potential roles for CDR in overall strategies for lowering the concentrations of warming pollutants in the atmosphere.

The second general category of climate intervention proposals is albedo modification (AM). It involves cooling Earth by reflecting sunlight away from the planet. Most AM research has focused on putting reflective particles into the upper atmosphere or seeding clouds in the lower atmosphere to brighten them. AM cannot substitute for reductions in greenhouse gas emissions, because its effects on the climate are not simply to reverse warming and because it would have no direct effect on ocean acidification caused by increasing carbon dioxide levels.

However, in theory, it could reduce some harm done by climate change during the time it takes for societies to implement deep cuts in greenhouse gas emissions while also potentially developing and deploying CDR systems. It could also, in theory, cool the climate quickly and thus prove highly valuable should society at some point face rapid changes in climate that cause unacceptable damage.

AGU urges national funding agencies to create substantial research programs on AM and to embed them, where appropriate, in existing larger programs on climate science because much of the knowledge needed to understand AM systems overlaps heavily with the knowledge needed to understand the changing climate system. Since 2009, several groups have advocated AM research programs. These include the U.S. National Academies,iv whose findings on this topic AGU endorses. Such research, if conducted openly with introspection and self-scrutiny as befits the global scientific community, could help diffuse information widely and also help facilitate the development of appropriate international norms about testing and evaluation of AM systems. AGU is concerned that scientific discussions around AM are taking place mainly in a small number of western countries. A proper and full evaluation of potential uses and impacts of AM will require a broader dialogue that engages more societies and the broader public.

While much can be learned from laboratory and modeling research, AGU finds that robust AM research programs must recognize that important advances in knowledge may also require field experiments. Decisions about where and how to conduct field experiments are best left to competent authorities that already oversee such questions; where adequate national oversight does not exist, active efforts will be needed to build that capacity.

AGU is concerned that the debate over research funding for CDR and AM has been prone to paralysis. While legitimate concerns have been raised about scalability and the side effects of climate intervention schemes, those same concerns have been used to block funding of the research that could help understand and address them. The reality is that climate change is happening, and it too creates risks; balancing those risks is essential to effective policy strategies. There are currently no large public research programs on climate intervention and only a few private sector efforts aimed at advancing particular technologies. Public sector research programs are essential to ensuring transparency and an adequate coverage and level of research support.

CDR and AM cannot substitute for deep cuts in emissions or the need for adaptation, but it is possible that they could contribute to a comprehensive risk-management strategy aimed at reducing the harms of climate change.

Adopted by AGU on 12 January 2018. Based on an earlier statement adopted by AGU on 13 December 2009 in collaboration with the American Meteorological Society (as adopted by the AMS Council on 20 July 2009) which was revised and reaffirmed February 2012.

i AGU White Paper 2017: Climate Intervention Requires Enhanced Research, Consideration of Societal Impacts, and Policy Development.

ii Shepherd, J. G. S., et al., 2009: Geoengineering the climate: Science, governance and uncertainty, RS Policy Document 10/09 (London: The Royal Society).

iii National Research Council, 2015: Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration (Washington, DC: The National Academies Press) https://doi.org/10.17226/18805

iv National Research Council, 2015: Climate Intervention: Reflecting Sunlight to Cool Earth (Washington, DC: The National Academies Press) https://doi.org/10.17226/18988