Dependence of strategic solar climate intervention on background scenario and model physics

Model dependence in simulated responses to stratospheric aerosol injection (SAI) is a major uncertainty surrounding the potential implementation of this solar climate intervention strategy. We identify and aim to understand the drivers of large differences in the aerosol mass latitudinal distributions between two recently produced climate model SAI large ensembles using two models from the same modeling center despite using similar climate targets and controller algorithms. Using a hierarchy of recently produced simulations, we identify three main contributors to the differences including (1) the rapid adjustment of clouds and rainfall to elevated levels of carbon dioxide, (2) the low-frequency dynamical responses in the Atlantic meridional overturning circulation, and (3) the contrasts in future background forcing scenarios. Each uncertainty is unlikely to be significantly narrowed over the likely timeframe of a potential SAI deployment if a 1.5 ∘C target of global warming over preindustrial conditions is to be met.