Data from: Hemispherically-Symmetric Strategies for Stratospheric Aerosol Injection

Data in support of research: Stratospheric aerosol injection (SAI) comes with a wide range of possible design choices, such as where and when to inject aerosols. Different injection strategies can yield different climate responses; therefore, making informed future decisions on SAI requires an understanding of the range of possible climate outcomes. Yet to date, there has been no systematic exploration of a comprehensive set of SAI strategies. This limits the ability to determine what effects are robust across different strategies and what depend on specific injection choices, or to determine if there are underlying trade-offs between different climate goals. This study systematically explores how the choice of SAI strategy affects climate responses. Here, we introduce four hemispherically-symmetric injection strategies, all of which are designed to maintain the same global mean surface temperature: an annual injection at the equator (EQ), an annual injection of equal amounts of SO2 at 15N and 15S (15N+15S), an annual injection of equal amounts of SO2 at 30N and 30S (30N+30S), and a polar injection strategy that injects equal amounts of SO2 at 60N and 60S only during spring in each hemisphere (60N+60S). We compare these four hemispherically-symmetric SAI strategies with a more complex injection strategy that injects different quantities of SO2 at 30N, 15N, 15S, and 30S in order to maintain not only the global mean surface temperature but also its large scale horizontal gradients. We find that the choice of SAI strategies notably affects the spatial distribution of aerosol optical depth (AOD), injection efficiency, and various surface climate responses. Among other findings, injecting at mid-latitudes produces more global cooling per unit injection, with the EQ and the 60N+60S cases requiring, respectively, 59% and 50% more injection than the 30N+30S case to meet the same global mean temperature target. Injecting at higher latitudes results in larger equator-to-pole temperature gradients. While all five strategies restore September Arctic sea ice, the high-latitude injection one is more effective due to the SAI-induced cooling more focused at higher latitudes