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