The Choice of Baseline Period Influences the Assessments of the Outcomes of Stratospheric Aerosol Injection

Abstract The specifics of the simulated injection choices in case stratospheric aerosol injections (SAI) are part crucial context necessary for meaningfully discussing impacts that a deployment SAI would have on planet. One main is desired amount cooling aiming to achieve. Previous simulations usually either fixed injection, resulting warming being offset, or specified one target temperature, so only dependent underlying trajectory greenhouse gases. Here, we use three sets achieving different amounts global mean surface while following middle‐of‐the‐road gas emission trajectory: scenario maintains temperatures at 1.5°C above preindustrial levels (PI), and two other scenarios which achieve additional 1.0°C 0.5°C PI. We demonstrate various scale proportionally with respect cooling, such as precipitation changes, changes Atlantic Meridional Overturning Circulation Walker Cell. also highlight importance choice baseline period when comparing responses another pathway. This analysis leads policy‐relevant discussions around concept reference altogether, what constitutes relevant, significant, change produced by SAI.