Enhancing Climate Model Performance through Improving Volcanic Aerosol Representation

Abstract. An accurate representation of Earth's surface temperature is crucial for simulating climate change. Yet many climate models struggle to reproduce the evolution of historical temperature records, especially after the major 1963 Mt. Agung volcano eruption. This study investigates whether the method of specifying the volcanic forcing could be contributing to this bias using the Energy Exascale Earth System Model (E3SM). The CMIP6 protocol represents volcanic eruptions through simplified radiative forcing, neglecting the interaction between volcanic aerosols and clouds. Here we adopt a new approach based on an updated volcanic eruption inventory, which includes volcanic sulfur dioxide emissions and hence allows for a more realistic representation of subsequent physical processes that involve volcanic aerosols. With this new approach, E3SM simulates slightly warmer surface temperatures and improved interannual variability during years 1940–1980 compared to the standard CMIP6 approach. The improvements mainly stem from two factors: 1) the inclusion of volcanic aerosol-cloud interactions, which reduces aerosol indirect effect by volcanic quiescent warming effect, and 2) the more accurate representation of volcanic eruptions after 1963, which leads to less volcanic aerosol cooling. Overall, this study highlights the importance of more accurate volcanic forcing in improving climate simulation and is strongly in favor of an emission-based volcanic forcing treatment.