Quantifying future volcanic impacts on climate projections and their uncertainties using stochastic volcanic emissions
Explosive volcanic eruptions can inject sulfur dioxide into the stratosphere, forming sulfate aerosols that alter Earth’s radiative balance leading to abrupt climatic changes. Despite the importance of volcanic stratospheric aerosols for climate, current climate projection studies rely on two simplified assumptions: (i) that future volcanic forcing is represented well by a constant forcing, and (ii) that future forcing has a magnitude equivalent to historical mean volcanic forcing between 1850 and 2014. These assumptions fail to capture the sporadic nature of volcanic eruptions and do not represent the recurrence frequency of small-magnitude eruptions and large-magnitude eruptions in the longer term well, potentially leading to underestimation of the volcanic effects on climate. To address current limitations in the way future volcanic forcing is represented in climate models, this thesis develops a novel modelling framework, UKESM VPLUME, which couples a volcanic plume model with an Earth System Model (Chapter 2). UKESM-VPLUME is then used in combination with an innovative approach to generate stochastic future eruption scenarios from 2015 to 2100 based on statistical resampling of ice cores and satellite volcanic emission records spanning the past 11,500 years. The results of this thesis demonstrate a 95% probability that future volcanic forcing between 2015 and 2100 will exceed the historical mean value used in previous studies, highlighting the need for improved representation of volcanic forcing in climate projections. The simulations using the stochastic volcanic forcing also reveal that future volcanic eruptions (i) lead to greater variability in large-scale climate indicators compared to constant forcing (Chapter 3); (ii) potentially delay the recovery of the Antarctic ozone layer (Chapter 4); and (iii) contribute to a significant fraction of the total uncertainty in temperature projections (Chapter 5). Overall, this thesis highlights the importance of accounting for the sporadic nature of volcanic eruptions and improving its representation in climate projections to better account for the effects of volcanic eruptions on climate, atmospheric composition, and socio-economic risk assessments.
Climate projections, Volcanic aerosols, Volcanic forcing
Networked Digital Library of Theses and Dissertations