This study is among the first modeling studies on stratospheric sulfate geoengineering that interactively couple a size-resolved sectional aerosol module to well-described stratospheric chemistry and radiation schemes in a global 3-D chemistry–climate model. We found that compared with SO₂ injection, the direct emission of aerosols results in more effective radiative forcing and that sensitivities to different injection strategies vary for different forms of injected sulfur.