Publications

Publications

Harvard’s Solar Geoengineering Research Program seeks to advance natural and social science research on solar geoengineering. The following academic and non-technical publications highlight some of the latest findings.

Academic Publications

Clark, Britta. “How to Argue about Solar Geoengineering.” Journal of Applied Philosophy 40, no. 3 (2023): 505-520. Publisher's VersionAbstract
Should high-income countries engage in solar geoengineering research and possible deployment? On the assumption that the speed of the energy transition will be insufficient to abate catastrophic climate impacts, research into solar geoengineering begins to look like a technically and socially feasible route to mitigate such impacts. But on the assumption that a rapid and relatively just energy transition is still within the realm of political possibility, research into solar geoengineering looks more like an ideological tool designed to divert time and resources from less risky climate solutions. At the heart of debates over solar geoengineering, then, is disagreement over what political actors can be expected to do in the future. In this article, I argue that both objectors to and proponents of solar geoengineering research often make background assumptions regarding expected future actions that are either (a) inaccurate or (b) inconsistent. I propose an account of expected future actions that avoids these problems and sketch what the debate over solar geoengineering looks like with these assumptions in place.
Harding, Anthony R., Mariia Belaia, and David W. Keith. “The value of information about solar geoengineering and the two-sided cost of bias.” Climate Policy 23, no. 3 (2023): 355-365. Publisher's VersionAbstract
Solar geoengineering (SG) might be able to reduce climate risks if used to supplement emissions cuts and carbon removal. Yet, the wisdom of proceeding with research to reduce its uncertainties is disputed. Here, we use an integrated assessment model to estimate that the value of information that reduces uncertainty about SG efficacy. We find the value of reducing uncertainty by one-third by 2030 is around $4.5 trillion, most of which comes from reduced climate damages rather than reduced mitigation costs. Reducing uncertainty about SG efficacy is similar in value to reducing uncertainty about climate sensitivity. We analyse the cost of over-confidence about SG that causes too little emissions cuts and too much SG. Consistent with concerns about SG’s moral hazard problem, we find an over-confident bias is a serious and costly concern; but, we also find under-confidence that prematurely rules out SG can be roughly as costly. Biased judgments are costly in both directions. A coin has two sides. Our analysis quantitatively demonstrates the risk-risk trade-off around SG and reinforces the value of research that can reduce uncertainty.
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 VersionAbstract

Solar geoengineering (SG), or the proposed use of technology to reflect sunlight back to space as a means of partially counteracting climate change, requires systematic research funded by public bodies, yet no dedicated national SG research programs (“programs”) currently exist. To explain why and understand how things might change in the future, we add concepts from role theory, a research tradition focused on international relations and foreign policy analysis, to the Multiple Streams Approach, a theoretical framework devel- oped to study agenda setting at the national level, to assess policy processes related to SG research in four countries: Germany, China, Australia, and the United States (US). The results of our analysis indicate that, among these four states, only the US might plausi- bly consider initiating a program under present conditions. Germany, China, and Australia appear likely to seriously consider comparable efforts only in response to a US program, although their reasons for doing so and specific program designs would differ. The source of this variation, we argue, is the different foreign policy paradigms—or “national role conceptions”—prevailing in each state, which mediate between domestic and international politics and help define which policy proposals qualify as viable in different countries. From a policy perspective, this suggests that the global trajectory of SG depends disproportionately on developments in the US.

Rabitz, Florian, Marian Feist, Matthias Honegger, Joshua Horton, Sikina Jinnah, and Jesse Reynolds. “A preliminary framework for understanding the governance of novel environmental technologies: Ambiguity, indeterminateness and drift.” Earth System Governance 12 (2022). Publisher's VersionAbstract

We propose a conceptual framework to explain why some technologies are more difficult to govern than others in global environmental governance. We start from the observation that some technologies pose transboundary environmental risks, some provide capacities for managing such risks, and some do both. For “ambiguous” technologies, potential risks and risk management capacities are uncertain, unknown or even unknowable. Governance systems are indeterminate towards ambiguous technologies, as existing norms, rules, scripts and routines do not imply default solutions under institutional focal points. Indeterminateness can lead to institu- tional drift, with risks accordingly remaining unmitigated and risk management capacities remaining unex- ploited. We use the cases of solar geoengineering, gene drive systems and bioinformatics for illustrating this framework. As technological ambiguity may often be irresolvable, we conclude that it might force us to confront the limits to anticipatory global decision-making on matters of long-term environmental sustainability.

Belaia, Mariia, Juan B. Moreno-Cruz, and David W. Keith. “Optimal Climate Policy in 3D: Mitigation, Carbon Removal, and Solar Geoengineering .” Climate Change Economics 12, no. 3 (2021). Publisher's VersionAbstract
We introduce solar geoengineering (SG) and carbon dioxide removal (CDR) into an integrated assessment model to analyze the trade-offs between mitigation, SG, and CDR. We propose a novel empirical parameterization of SG that disentangles its efficacy, calibrated with climate model results, from its direct impacts. We use a simple parameterization of CDR that decouples it from the scale of baseline emissions. We find that (a) SG optimally delays mitigation and lowers the use of CDR, which is distinct from moral hazard; (b) SG is deployed prior to CDR while CDR drives the phasing out of SG in the far future; (c) SG deployment in the short term is relatively independent of discounting and of the long-term trade-off between SG and CDR over time; (d) small amounts of SG sharply reduce the cost of meeting a 2∘2°C target and the costs of climate change, even with a conservative calibration for the efficacy of SG.
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Non-Technical Publications

Burns, Lizzie, David Keith, Peter Irvine, and Joshua Horton. “Belfer Technology Factsheet Series: Solar Geoengineering” (2019).Abstract
Solar geoengineering refers to a set of emerging technologies that could alter the Earth’s radiative balance— perhaps through injecting aerosols into the stratosphere, where they would reflect a small fraction of sunlight back into space—reducing the amount of climate change caused by greenhouse gases. It could not replace reducing emissions (mitigation), coping with a changing climate (adaptation), or carbon dioxide removal (CDR). Yet it does have the potential to supplement these efforts, and it might provide reductions in climate risk that are unachievable by other means.
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