The choice of baseline period influences the assessments of the outcomes of Stratospheric Aerosol Injection
Journal Article
Overview
abstract
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.
