Resilient Stratospheric Aerosol Injection is Cooperative

For stratospheric aerosol injection (SAI) to reduce climate risks across the globe without producing new or exacerbating current inequalities, it must be resilient to unpredictable or even malicious disturbances (e.g., disasters, pandemics, fascists). Two significant risks which arise from mismanaged SAI are termination shock (an abrupt termination after substantial warming is being avoided) and significant changes in large-scale tropical circulation patterns, including shifts in the Intertropical Convergence Zone (ITCZ) due to unbalanced cooling. In this paper, we use a state-of-the-art climate emulator capable of simulating the global and regional climate responses of cooperative and noncooperative SAI deployment. We show that SAI without the risk of termination shock or ITCZ shift must be a cooperative and global endeavor. Given the rapidly growing interest in SAI, a widespread understanding of the frailty of unilateral deployment and a desire for cooperation would help shape current and future discussion of geoengineering into a collaboration instead of an arms race.