Journal Article

Climate Projections Very Likely Underestimate Future Volcanic Forcing and Its Climatic Effects

Schmidt, Anja, Walton, Jeremy, Aubry, Thomas J., Marshall, Lauren, Mulcahy, Jane, Chim, Man Mei, Abraham, Nathan Luke

2023

Overview

Standard climate projections represent future volcanic eruptions by a constant forcing inferred from 1850 to 2014 volcanic forcing. Using the latest ice‐core and satellite records to design stochastic eruption scenarios, we show that there is a 95% probability that explosive eruptions could emit more sulfur dioxide (SO2) into the stratosphere over 2015–2100 than current standard climate projections (i.e., ScenarioMIP). Our simulations using the UK Earth System Model with interactive stratospheric aerosols show that for a median future eruption scenario, the 2015–2100 average global‐mean stratospheric aerosol optical depth (SAOD) is double that used in ScenarioMIP, with small‐magnitude eruptions (<3 Tg of SO2) contributing 50% to SAOD perturbations. We show that volcanic effects on large‐scale climate indicators, including global surface temperature, sea level and sea ice extent, are underestimated in ScenarioMIP because current climate projections do not fully account for the recurrent frequency of volcanic eruptions of different magnitudes. Plain Language Summary Climate projections are the simulations of Earth's climate in the future using complex climate models. Standard climate projections, as in Intergovernmental Panel on Climate Change Sixth Assessment Report, assume that explosive volcanic activity over 2015–2100 are of the same level as the 1850–2014 period. Using the latest ice‐core and satellite records, we find that explosive eruptions could emit more sulfur dioxide into the upper atmosphere for the period of 2015–2100 than standard climate projections. Our climate model simulations show that the impacts of volcanic eruptions on climate, including global surface temperature, sea level and sea ice extent, are underestimated because current climate projections do not fully account for the recurrent frequency of volcanic eruptions. We also find that small‐magnitude eruptions occur frequently and can contribute a significant effect on future climate. Key Points There is a 95% chance that the time‐averaged 2015–2100 volcanic SO2 flux from explosive eruptions exceeds the time‐averaged 1850–2014 flux Standard climate projections very likely underestimate the 2015–2100 stratospheric aerosol optical depth and volcanic climate effects Small‐magnitude eruptions (<3 Tg SO2) contribute 30%–50% of the volcanic climate effects in a median future eruption scenario

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Aerosol optical depth / Aerosols / aerosol‐climate modeling / Atmospheric models / climate / Climate change / Climate effects / Climate models / Earth / earth system model / Eruptions / Future climates / Global aerosols / Global temperatures / Interactive systems / Lava / Optical analysis / Optical thickness / Perturbation / Probability theory / Records / Satellites / Sea ice / Sea ice temperatures / Sea level / Simulation / Stratosphere / Stratospheric aerosols / Sulfur / Sulfur dioxide / Sulphur / Sulphur dioxide / Surface temperature / Upper atmosphere / Volcanic activity / Volcanic eruption effects / Volcanic eruptions