Abstract
Explosive volcanic eruptions affect climate, but how climate change affects the stratospheric volcanic sulfate aerosol lifecycle and radiative forcing remains unexplored. We combine an eruptive column model with an aerosol-climate model to show that the stratospheric aerosol optical depth perturbation from frequent moderate-magnitude tropical eruptions (e.g. Nabro 2011) will be reduced by 75% in a high-end warming scenario compared to today, a consequence of future tropopause height rise and unchanged eruptive column height. In contrast, global-mean radiative forcing, stratospheric warming and surface cooling from infrequent large-magnitude tropical eruptions (e.g. Mt. Pinatubo 1991) will be exacerbated by 30%, 52 and 15% in the future, respectively. These changes are driven by an aerosol size decrease, mainly caused by the acceleration of the Brewer-Dobson circulation, and an increase in eruptive column height. Quantifying changes in both eruptive column dynamics and aerosol lifecycle is therefore key to assessing the climate response to future eruptions.
Highlights
Explosive volcanic eruptions affect climate, but how climate change affects the stratospheric volcanic sulfate aerosol lifecycle and radiative forcing remains unexplored
Our simulations for the moderate-magnitude tropical eruption case suggest damping of the peak global-mean stratospheric aerosol optical depth (SAOD) anomaly by a factor of 4 in a high-end future climate scenario (SSP585)
We project a decrease of the background tropical stratospheric aerosol layer, which is largely governed by sulfur injections by moderate-magnitude eruptions, and the radiative forcing it exerts on climate[17,18]
Summary
Explosive volcanic eruptions affect climate, but how climate change affects the stratospheric volcanic sulfate aerosol lifecycle and radiative forcing remains unexplored. Global-mean radiative forcing, stratospheric warming and surface cooling from infrequent large-magnitude tropical eruptions (e.g. Mt. Pinatubo 1991) will be exacerbated by 30%, 52 and 15% in the future, respectively. Tg of sulfur dioxide (SO2) or more into the stratosphere and with a volcanic explosivity index[6] (VEI) greater than five are relatively rare events, with a return frequency on the order of decades[2,6,7] They can, have a profound impact on climate, such as the Mount Tambora 1815 eruption, which was followed by the “year without a summer[8,9], or the Mount Pinatubo 1991 eruption, which resulted in 0.4–0.5 °C of global-mean lower-tropospheric cooling for over a year[10]. A cluster of such eruptions during 2005–2015 had a discernable cooling effect on lower tropospheric and sea surface temperatures[3,17,18]
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