A Potential Surface Warming Regime for Volcanic Super-Eruptions Through Stratospheric Water Vapor Increases

Abstract

Large volcanic eruptions are known to influence the climate through a variety of mechanisms including aerosol-forced cooling and warming via emitted CO₂. The January 2022 Hunga shallow underwater eruption caused an increase in stratospheric water vapor, and demonstrated how the associated positive radiative forcing can be an important component of an eruption's climate forcing. We present interactive stratospheric aerosol model simulations of super-volcanic eruptions with a range of SO₂ emissions that can produce climate warming through feedback effects produced by a large igneous province (or “flood basalt”) mid-latitude super-eruption using Goddard Earth Observing System Chemistry Climate Model climate model simulations. The model experiments suggest total SO₂ emissions ≳4,000 Tg/4 Gt generate a multi-year period of sustained aerosol absorptive local-heating of the upper troposphere and lower stratosphere and hence produce net climate warming after strong initial cooling. The eruptions produce stratospheric water vapor increases of factors of 8–600. The initiation of these feedbacks within the simulations suggest they could occur for individual stratovolcano eruptions of the scale of the Toba or Tambora eruptions. We note the sensitivity of our results to volcanic sulfate aerosol microphysics and model chemistry.