International Climate Agreements under The Threat of Solar Geoengineering

This working paper uses a game theory model to analyze how opportunities to deploy solar geoengineering measures impact international climate goals and environmental agreements.



Sept. 5, 2023


David McEvoy, Matthew McGinty, Todd Cherry, and Stephan Kroll


Working Paper

Reading time

1 minute


The possibility of overshooting global emissions targets has triggered a public debate about the role solar geoengineering (SGE) - using technologies to reflect solar radiation away from Earth - may play in managing climate change. One major concern is that SGE technologies are relatively cheap, and could potentially be deployed by a single nation (the “free driver”) that could effectively control the global climate. Another concern is that SGE opportunities may alter countries’ incentives to cooperate on abatement. Here we develop a game-theoretic model to analyze how opportunities to deploy SGE impact global abatement and the effectiveness of international environmental agreements (IEAs) on climate change. We show that non-cooperative abatement levels may increase or decrease under the threat of SGE, depending on how damaging the free-driver’s level of deployment is on others. We also show the stability of IEAs that govern abatement is challenged by two competing strategic incentives. One is a familiar free-rider incentive, which is the benefit a country earns by leaving an agreement and lowering its abatement. The other incentive is the benefit a country earns by joining an agreement and increasing abatement in order to motivate the free-driver to reduce its level of deployment. We introduce the term anti-driver to describe this second incentive. Ultimately, we find that if the anti-driver incentives are high enough, the threat of SGE can expand both the depth (i.e., abatement level) and breadth (i.e., participation level) of stable IEAs compared to a world without SGE.


David McEvoy

Appalachian State University

Matthew McGinty

University of Wisconsin-Milwaukee

Todd Cherry

University of Wyoming

Stephan Kroll

Colorado State University

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