Climate Response to Latitudinal and Altitudinal Distribution of Stratospheric Sulfate Aerosols

Abstract

Stratospheric aerosol injection is one of the most widely studied solar radiation modification methods to reduce some effects of anthropogenic warming. We perform idealized simulations to analyze climate response to different latitudinal and altitudinal distributions of additional stratospheric sulphate aerosols. We analyze climate response to both large volcanic‐size aerosols that are representative of sulphate aerosols which form when SO 2 is injected into the stratosphere by major volcanic eruptions or by proposed stratospheric sulphate aerosol geoengineering option, and small background‐size aerosols which are present in the stratosphere during quiescent periods with no major volcanic eruptions. Our simulations show that under the climate state with doubled atmospheric CO 2, for the same total mass, independent of size‐distributions, aerosols concentrated at higher latitudes produce less negative effective radiative forcing but larger surface cooling as a result of larger forcing efficacy. For the same latitudinal distribution, small background‐size aerosols added at lower altitudes cause larger surface cooling as a result of hygroscopic growth that increases scattering of sunlight. In contrast, large volcanic‐size aerosols added at lower altitudes cause smaller surface cooling than at higher altitudes as a result of enhanced stratospheric heating and associated water vapor feedback that enhance absorption of solar and terrestrial radiation. For both background‐size and volcanic‐size aerosols, asymmetric distributions about the equator induce substantial cross‐equatorial energy transport, causing the Intertropical Convergence Zone to move to the warmer hemisphere with less aerosol loading. Our study helps to understand the climate consequences of different spatial patterns and size distributions of stratospheric aerosol perturbation.