Abstract

AbstractVolcanic eruptions are an important climate driver. The impact of Pinatubo‐sized eruptions has been observed and is well constrained. The magnitude and duration of volcanic winter effects after supereruptions such as Toba remain disputed due to disagreement between the strong cooling predicted by models and much milder climate perturbations according to the paleodata. Here we present a reevaluated climate impact of a Toba‐sized supereruption based on up‐to‐date GISS ModelE simulations. In this study, we account for all known primary mechanisms that govern the evolution of the volcanic plume and their nonlinear interactions. The SO radiative effects are evaluated for the first time in coupled climate simulations with the interactive atmospheric chemistry module. We found that SO effects on photochemistry, dynamics, and radiative forcing are especially prominent. Due to strong absorption in ultraviolet, SO feedback on photochemistry partially offsets the limiting effect associated with aerosol microphysical processes. SO greenhouse warming soothes the radiative cooling exerted by sulfate aerosols. SO absorption in the shortwave and longwave causes radiative heating and lofting of the volcanic plume, and boosts the efficiency of SO impact on photochemistry. Our analysis shows that SO lifetime and magnitude of effects scale up and increase with the amount of emitted material. For a Pinatubo‐sized eruption, SO feedbacks on chemistry and dynamics are relevant only during the initial stage of the volcanic plume evolution, while local SO concentrations are high. For a Toba‐sized eruption, SO effects are as important as sulfate aerosols and produce a less extreme volcanic winter.

Highlights

  • The largest stratovolcanic eruptions, known as “supereruptions,” have the potential to alter Earth's climate significantly

  • In this work we present an updated estimate of a Toba-sized volcanic eruption impact on climate

  • We found that for the Toba case, the SO2 radiative effect is as important as that of sulfate aerosols

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Summary

Introduction

The largest stratovolcanic eruptions, known as “supereruptions,” have the potential to alter Earth's climate significantly. The extreme cooling during the posteruption “volcanic winter” is the key component that initially drew attention to the Toba eruption and linked it to two major hypotheses: the human genetic bottleneck (Ambrose, 1998) and the accelerated shift to glacial conditions (Rampino & Self, 1992). Since these theories have been tested by models and available observations, but the conclusions remain disputed and controversial. The comprehensive intercomparison of these mechanisms is a primary focus of this work

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