Open-source code

The paper data, data generation scripts, and supporting 2d simulation code are provided in their entirety in the provided GitHub repository, allowing full reproduction of the results presented in the manuscript

Abstract

Solid-particle alternatives to sulfate for stratospheric aerosol injection (SAI) span a broad design space: particle composition and morphology, sensitivities to agglomerate microphysics, and injection strategies in latitude, altitude, and season. Spanning this space with three-dimensional chemistry–climate models is practically prohibitive. To enable such sweeps, we present a two-dimensional (2-D) zonal-mean modelling framework for SAI with solid-particle materials. ERA5-constrained stratospheric transport is coupled with explicit aerosol microphysics and a modified RRTMG radiative transfer scheme, with each component extensively validated. Focusing on silica and calcite, we use the framework to explore SAI performance across two complementary axes: material properties together with monomer and agglomerate microphysics, and injection strategies in space and time. Tropical injection maximises radiative forcing efficacy but pays the largest in-layer heating penalty. Coagulation in the tropical confinement amplifies aggregate diameters and partially offsets the residence-time advantage. A seasonal (alternating-summer-hemisphere) schedule delivers a modest ∼ 10–30% mid-latitude cooling-efficacy gain over symmetric injection, but at a comparable mid-latitude heating-cost penalty. For IR-absorbing materials such as silica, symmetric mid-latitude injection reduces stratospheric heating with limited loss of efficacy; calcite’s negligible IR absorption keeps the heating penalty an order of magnitude lower across all injection strategies considered.