Climate response to off-equatorial stratospheric sulfur injections in three Earth system models – Part 1: Experimental protocols and surface changes

Abstract. There is now substantial literature on climate model studies of equatorial or tropical stratospheric SO2 injections that aim to counteract the surface warming produced by rising concentrations greenhouse gases. Here we present results from first systematic intercomparison responses in three Earth system models wherein injection occurs at different latitudes lower stratosphere: CESM2-WACCM6, UKESM1.0 and GISS-E2.1-G. The two use a modal aerosol microphysics scheme, while versions GISS-E2.1-G bulk (One-Moment Aerosol, OMA) two-moment (Multiconfiguration Aerosol TRacker mIXing state, MATRIX) approach, respectively. Our this work determine commonalities differences between terms distribution optically reflective sulfate aerosols oxidation response resulting reduction solar radiation. A focus understanding contribution characteristics transport alongside their microphysical chemical schemes, evaluating models, given companion paper (Bednarz et al., 2023). goal exercise not evaluate these single-point simulations as stand-alone proposed strategies global warming; instead sources areas agreement uncertainty simulated and, ultimately, possibility designing comprehensive intervention strategy capable managing multiple simultaneous goals through combination locations. We find large disagreements CESM2-WACCM6 regarding magnitude cooling per unit optical depth (AOD) produced, which varies 4.7 K AOD 16.7 version with microphysics. By normalizing mean each thus assuming amount injected free parameter can be managed independently, highlight some overall distributions aerosols, inter-hemispheric temperature shifts Intertropical Convergence Zone, well disagreement, such extent confinement region efficiency polar latitudes. In conclusion, demonstrate it possible produce more models. However, magnitudes expected, potentially increasing inter-model spreads quantities (such distribution) reducing spread precipitation; furthermore, selection locations may dependent models' specific transport.