Assessing the stratospheric temperature response to volcanic sulfate injections by Mt. Pinatubo: insights from the Interactive Stratospheric Aerosol Model Intercomparison Project

Some major volcanic eruptions, such as the one of Mt. Pinatubo in 1991, can inject large amounts of sulfur dioxide (SO₂) into the stratosphere, leading to a volcanic aerosol cloud. This dense aerosol cloud induces a radiative heating of the stratosphere, causing ozone and water vapour changes, thereby altering middle atmospheric dynamics and chemistry. The scale of these impacts for varying injection amounts and heights on stratospheric temperature anomalies is still highly uncertain. Here we analyse specially designed chemistry-climate model experiments following the Historical Eruptions SO₂ Emission Assessment Protocol (HErSEA) under the Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP). The results confirm our general understanding of the stratospheric aerosol forcing due to extra SO₂ injection, while simultaneously highlighting structural differences between models. Overall, for the Pinatubo-like experiments the multi-model mean temperature anomalies agree well with meteorological reanalysis data sets, and we find that in most cases, differences between models are larger than differences for individual models across experiments with varying injection amounts and altitudes. Differences in transport, radiative transfer, and microphysics as well as the characterisation of aerosol size distributions, play a crucial role in the emergence of the spread in the modelled temperature response. Our results show further that the sensitivity of the stratospheric temperature response to model selection is also apparent in other MIPs. Hence, we argue for caution in attribution studies and the interpretation of stratospheric aerosol injection experiments relying on individual or few models.