The Cluster is considering climate adaptation strategies to coastal erosion in Abidjan, Accra, and Lagos that would be technically feasible, that could be implemented, and that would ga.
Cluster Research Strengthening CommunitiesThe Cluster is examining the social costs and benefits of changes in the energy system, and propose concrete ways communities, firms, and governments to help them navigate the wide rang.
Cluster Research Climate Adaptation in South AsiaThe purpose of this Cluster is to advance climate adaptation research and implementation at the household, community, state, and federal levels in South Asia, particularly in the contex.
Cluster Research Corporate Net-Zero Targets ProjectA rapidly growing number of businesses are announcing greenhouse gas emissions reductions targets, including net-zero goals. Corporate progress on net-zero and other emissions reduction.
Cluster Research Reducing Global Methane EmissionsThe Cluster is seeking meaningful and sustained progress in global methane emissions reductions through research and effective engagement with policymakers in government and key stakeho.
The Harvard Solar Geoengineering Research Program (SGRP) produces knowledge to help society decide whether—and if so, how—solar geoengineering should play a role in global efforts to manage the growing risks from climate change.
The Harvard Solar Geoengineering Research Program (SGRP) aims to reduce uncertainties surrounding solar geoengineering; generate critical science, technology, and policy insights; and help inform the public debate surrounding this controversial idea. Recognizing that solar geoengineering could not be a replacement for reducing emissions or adapting to climate impacts, SGRP draws on Harvard’s research capabilities and global convening power to provide the knowledge necessary in considering solar geoengineering as a supplement to broader mitigation and adaptation efforts. SGRP supports a broad array of natural science, social science, and humanities research, both at Harvard and in collaboration with other academic, civil society, and government organizations and institutions.
Harvard has been engaged on the topic of solar geoengineering for decades:
The Harvard Solar Geoengineering Research Program (SGRP) was launched in April 2017. Since its establishment, SGRP has supported research resulting in the publication of dozens of peer-reviewed articles on the science and governance of solar geoengineering, as well as multiple non-technical publications (see ‘publications’ tab). SGRP hosts workshops, seminars, forums, and speakers covering solar geoengineering from a wide variety of natural science, social science, and humanities perspectives. SGRP provided funding and support to the Stratospheric Controlled Perturbation Experiment (SCoPEx), which ended in March 2024.
GeoengineeringGeoengineering refers to a set of emerging technologies that could manipulate the environment and partially offset some of the impacts of climate change. Solar geoengineering in particular could not be a replacement for reducing emissions (mitigation) or coping with a changing climate (adaptation); yet, it could supplement these efforts.
Geoengineering is conventionally split into two broad categories: The first is carbon geoengineering, often also called carbon dioxide removal (CDR). The other is solar geoengineering, often also called solar radiation managmenet (SRM), albedo modification, or sunlight reflection.
There are large differences:
Carbon geoengineering seeks to remove carbon dioxide from the atmosphere, which would address the root cause of climate change — the accumulation of carbon dioxide in the atmosphere. In the chain from emissions to concentrations to temperatures to impacts, it breaks the link from emissions to concentrations.
Solar geoengineering seeks to reflect a small fraction of sunlight back into space or increase the amount of solar radiation that escapes back into space to cool the planet. In contrast to carbon geoengineering, solar geoengineering does not address the root cause of climate change. It instead aims to break the link from concentrations to temperatures, thereby reducing some climate damages.
There are several proposed solar geoengineering technologies. These include marine cloud brightening, cirrus cloud thinning, space-based techniques, and stratospheric aerosol scattering, amongst others.
Marine cloud brightening would attempt to brighten marine clouds to reflect more sunlight back into space.
Cirrus cloud thinning would attempt to reduce the thin, high-altitude cirrus clouds to emit more long-wave radiation from the earth to space.
Space-based technologies would attempt to reflect a small fraction of sunlight away from the earth by positioning sun shields in space.
Lastly, stratospheric aerosol scattering would introduce tiny reflective particles, such as sulfate aerosols or perhaps calcium carbonate, into the upper atmosphere, where they could scatter a small fraction of sunlight back into space.
More information can be found on the Technology Factsheet: Solar Geoengineering from the Harvard Belfer Center and Center for Research on Computation and Society (CRCS).
Climate models have consistently shown that solar geoengineering, when used in moderation and combined with emissions cuts, has the potential to reduce climate changes around the globe. For example, it could reduce climate impacts such as extreme temperatures, changes in water availability, and intensity of tropical storms.
However, any benefits come with novel risks and significant uncertainty. For example, while the latest science might show some benefits globally, local impacts could vary more widely. There are a lot of other scientific uncertainties that are not yet well understood, not least the enormous governance challenges.
Also, solar geoengineering (largely) does not address ocean acidification. Every year, the ocean absorbs about one-quarter of the carbon dioxide we emit into the atmosphere, changing the chemistry of the oceans and harming marine ecosystems. Given that solar geoengineering would not remove carbon dioxide from the atmosphere directly, but rather reflect sunlight back to space, it could do little to address this serious problem except via carbon cycle feedbacks, the process through which additional carbon is emitted into the atmosphere upon additional warming.
That said, solar geoengineering could reduce rising temperatures, offsetting many impacts on the oceans. For example, by reducing sea surface temperatures, it could reduce the risk of coral bleaching events and help to maintain conditions favorable for coral reefs (as the damage to coral reefs is largely caused by rising sea surface temperatures, followed by intensifying ocean acidification). Solar geoengineering could also reduce poleward shifts in species ranges, which has been posing serious risks to tropical fisheries. And it could lessen the amount of sea-ice loss, which could reduce the impacts on high-latitude ecosystems and climate, and help to limit changes in ocean circulation and glacier melt.
In any case, solar geoengineering could not be a substitute for cutting carbon dioxide pollution. It could only be a potential supplement.
Research could reduce uncertainty about the technology’s potential benefits and risks, but, for decades, research in solar geoengineering has been limited. This has been in part because of a fear that it could lesson efforts to cut emissions. There have also been concerns pertaining to its ethics, governance, and potential impacts to the climate system. Recently the U.S. National Academy of Sciences and major environmental groups such as the Environmental Defense Fund and the Natural Resources Defense Council have begun to support careful research. The U.S. also published the Climate Science Special Report, which discussed geoengineering and called for further research. The report was a key part of the Fourth National Climate Assessment, which the U.S. Global Change Research Program (USGCRP) oversaw.
2023
Horton, Joshua B., Kerryn Brent, Zhen Dai, Tyler Felgenhauer, Oliver Geden, Jan McDonald, Jeffrey McGee, Felix Schenuit, and Jianhua Xu. “Solar geoengineering research programs on national agendas: a comparative analysis of Germany, China, Australia, and the United States.” Climatic Change 176 (2023). Publisher’s Version
2022
2021
Aldy, Joseph E, Tyler Felgenhauer, William A Pizer, Massimo Tavoni, Mariia Belaia, Mark E Borsuk, Arunabha Ghosh, et al. “Social science research to inform solar geoengineering: What are the benefits and drawbacks, and for whom?” Science 374, no. 6569 (2021): 815-818. Publisher’s Version
Fan, Yuanchao, Jerry Tjiputra, Helene Muri, Danica Lombardozzi, Chang-Eui Park, Shengjun Wu, and David Keith. “Solar geoengineering can alleviate climate change pressures on crop yields.” Nature Food 2, no. 5 (2021): 373-381. Publisher’s Version
Irvine, Peter, Elizabeth Burns, Ken Caldeira, Frank Keutsch, Dustin Tingley, and David Keith. “Expert judgments on solar geoengineering research priorities and challenges.” EarthArXiv (2021). Publisher’s Version
Dai, Zhen, Elizabeth Burns, Peter Irvine, Dustin Tingley, Jianhua Xu, and David Keith. “Elicitation of US and Chinese expert judgments show consistent views on solar geoengineering.” Humanities and Social Sciences Communications 8, no. 1 (2021). Publisher’s Version
Seeley, Jacob T., Nicholas J. Lutsko, and David W. Keith. “Designing a radiative antidote to CO2.” Geophysical Research Letters (2021). Publisher’s Version
2020
Harding, Anthony R., Katharine Ricke, Daniel Heyen, Douglas G. MacMartin, and Juan Moreno-Cruz. “Climate econometric models indicate solar geoengineering would reduce inter-country income inequality.” Nature Communications 11 (2020).
2019
Burns, Lizzie, David Keith, Peter Irvine, and Joshua Horton. “Belfer Technology Factsheet Series: Solar Geoengineering” (2019).
Heyen, Daniel, Joshua Horton, and Juan Moreno-Cruz. “Strategic implications of counter-geoengineering: Clash or cooperation?” Journal of Environmental Economics and Management 95 (2019): 153-177. Publisher’s Version
Irvine, Peter, Kerry Emanuel, Jie He, Larry Horowitz, Gabriel Vecchi, and David Keith. “Halving warming with idealized solar geoengineering moderates key climate hazards.” Nature Climate Change (2019). Publisher’s Version
2018
Horton, Joshua B., Jesse L. Reynolds, Holly Jean Buck, Daniel Callies, Stefan Schäfer, David W. Keith, and Steve Rayner. “Solar Geoengineering and Democracy.” Global Environmental Politics (2018): 5-24. Publisher’s Version
Mahajan, Aseem, Dustin Tingley, and Gernot Wagner. “Fast, cheap, and imperfect? U.S. public opinion about solar geoengineering.” Environmental Politics (2018). Publisher’s Version
Wagner, Gernot, and Martin Weitzman. “A Big-Sky Plan to Cool the Planet.” The Wall Street Journal, 2018. Publisher’s Version
MacMartin, Douglas G., Katharine L. Ricke, and David W. Keith. “Solar geoengineering as part of an overall strategy for meeting the 1.5°C Paris target.” Philosophical Transactions of the Royal Society 376, no. 2119 (2018).
2017
Sugiyama, Masahiro, Shinichiro Asayama, Atsushi Ishii, Takanobu Kosugi, John C. Moore, Jolene Lin, Penehuro F. Lefale, et al. “The Asia-Pacific’s role in the emerging solar geoengineering debate.” Climatic Change (2017).
Burns, Elizabeth, David Keith, Edward Parson, and Gernot Wagner, ed. Report on the Forum on U.S. Solar Geoengineering Research. Washington, D.C. 2017.
Keith, David W., Gernot Wagner, and Claire L. Zabel. “Solar geoengineering reduces atmospheric carbon burden.” Nature Climate Change 7 (2017): 617–619. Publisher’s Version
Mail:
Harvard’s Solar Geoengineering Research Program
Harvard University Center for the Environment
26 Oxford Street
Cambridge, MA 02138
Email:
Joshua Horton
Program Manager
horton@seas.harvard.edu
J. Baker Foundation
The Blue Marble Fund
OW Caspersen Foundation
The Crows Nest Foundation
The William and Flora Hewlett Foundation
Constance C. and Linwood A. Lacy Jr. Foundation
The Open Philanthropy Project
Pritzker Innovation Fund
Reflective Earth
Ronin Private Investments LLC
The Alfred P. Sloan Foundation
The Tansy Foundation
Teza Technologies LLC
VoLo Foundation
The Weatherhead Center for International Affairs
Laura and John Arnold
G. Leonard Baker, Jr.
Alan Eustace
Rob Fergus
Howard Fischer
Ross Garon
Bill Gates
Jonathan Golderg
The Imperial Family
Drew Myers
John Rapaport
Chris and Crystal Sacca
Michael Smith
Andrew Stark
Bill Trenchard
In addition to Harvard’s standard funding policies, SGRP follows two further policies:
We are concerned that fossil fuel companies or other interests will seek to exploit solar geoengineering as a pretext for delaying reductions in greenhouse gas emissions. We do not want donors who are (or could reasonably be construed as being) motivated to support solar geoengineering research to protect fossil fuel industries. For purposes of excluding such donors, we consider a rough weighting system as a guide. We rate the donor’s ties to fossil fuels on a 1 to 5 scale, where 1 has no connection with fossil fuels and 5 has nearly all of their current wealth and social connections tied to coal. Then, we rate the donor’s commitment to climate from 1 for a donor who has long devoted a majority of their time and resources to climate action to 5 for a donor who has no visible interest in climate. We then take the product of the two ratings, rejecting donors with a multiplicative combined rating that is larger than 10.
We would like to elaborate on this last point. We take issues of conflict of interest very seriously. And we take the “moral hazard” concern very seriously—the idea that research or even discussion on solar geoengineering could reduce incentives to mitigate. The world must reduce greenhouse emissions to zero, and remove carbon dioxide from the atmosphere, to address the root cause of climate change. Solar geoengineering does and will not change this fact.
We offer a few examples of our funding decisions:
