Patrick W Keys , Curtis M Bell

Climate change is causing increasingly alarming global impacts, such as rising temperatures and more severe storms. Despite this, current multilateral initiatives and agreements to systematically reduce greenhouse gas emissions are completely incommensurate with the scale of the problem. Thus, we explore the potential that some unilateral actor, finding present and near-future climate changes intolerable, may seek to respond to these changes through its own deliberate intervention in the climate. Focusing specifically on stratospheric aerosol injection (SAI), which is the dispersal of reflective particles in the stratosphere to reflect some of the sun’s energy away from Earth, we seek to identify the characteristics of states that might be most likely to modify the climate without broad international consensus. We develop a framework of geopolitically-relevant conditions that progressively reduce the number of candidate states, with the aim of identifying plausible unilateral SAI initiators. These conditions consider the state’s capacity to deploy SAI, variability in states’ motivations to change their local climates, the confidence that a deployment could be sustained and might produce the intended effects, and the state’s insensitivity to global condemnation, should the international community disapprove of this action. We provide a detailed explanation of each of these conditions along with discussion of potential candidate states. Our results highlight a concentration of states meeting all or most of these conditions in the vicinity of the Arabian Sea. Based on this finding, we conclude with a discussion of how this type of geopolitical scenario development can be integrated into social-physical simulations of geopolitically plausible climate intervention scenarios.