Stratospheric Sulfate Aerosol Geoengineering Could Alter the High‐Latitude Seasonal Cycle

Abstract Stratospheric aerosol geoengineering (SAG) has been proposed to reduce some impacts of anthropogenic climate change. Previous studies examined annual mean climate responses to SAG. Here we use the Stratospheric Aerosol Geoengineering Large Ensemble simulations to explore the effects of SAG on the seasonal cycle of climate change. Simulations show that relative to the present‐day climate, SAG diminishes the amplitude of the seasonal cycle of temperature at many high‐latitude locations, with warmer winters and cooler summers. The seasonal temperature shift significantly influences the seasonal cycle of snow depth and sea ice, with Arctic sea ice recovery overcompensated in summer by 52% and undercompensated in winter by 8%. We identify that both the dynamic effects of aerosol‐induced stratospheric heating and seasonal variations of sunlight contribute to the shifts in seasonal cycle. Shifts in the seasonal cycle have important ecological and environmental implications, which should be considered in geoengineering impact analysis.