In recent years, discussions of geoengineering have intensified among scientists, policymakers, and other interested observers. The possibility that one state might unilaterally deploy geoengineering technology has become a fixture in these debates, and has cast a pall over substantive inquiry into climate intervention research and implementation. Speculation about “rogue” states pursuing geoengineering outside multilateral frameworks has given pause to calls for more robust experiments and field trials, and has contributed to the adoption of moratoria by the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter of 1972 and the Protocol of 1996 (LC/LP) and the Convention on Biological Diversity (CBD).¹ In sum, the fear of unilateralism has become an idée fixe in conversations about geoengineering, in effect putting the brakes on more ambitious research efforts and deliberations about governance issues.

In this article, I argue that fear of unilateralism is largely misplaced, grounded more in unexamined policy assumptions than in reasoned analysis of the strategic situation faced by states. I will present this argument in five parts. First, I will document the widespread notion that unilateral geoengineering poses a genuine threat to the international order. Second, I will closely examine the interests and constraints that are likely to confront states contemplating intervention in the climate system. Third, I will demonstrate that international dynamics are more likely to create pressures leading to cooperation than to foster tendencies toward unilateralism. Fourth, I will consider different mechanisms for encouraging collaboration on climate intervention strategies. Finally, I will consider the implications of this argument for future discussions of geoengineering.