Modeling the Role of Volcanoes in the Climate System

Abstract

Volcanoes emit sulfur dioxide gas, which converts through a series of chemical and microphysical processes into sulfate aerosols that scatter incoming sunlight and cool the Earth. Understanding and modeling this natural forcing of the climate system adds confidence to the scientific consensus on climate change. I have spent a large portion of my doctoral research critically analyzing the inner details of global chemistry-climate models with interactive stratospheric aerosols (ISAs) when they simulate the aftermath of explosive volcanic eruptions, in the quest to find model errors that can be improved. I successfully identified physics and chemistry errors in models participating in the Model Intercomparison Project on the climatic response to Volcanic Forcing (VolMIP) Tambora ISA study that needed fixing. Modeling groups took action from the analysis (Clyne et al., 2021), reprinted here as Chapter 2 of my thesis. I used what I learned to then form my own Model Intercomparison Project, Tonga-MIP, when the Hunga Tonga-Hunga Ha'apai volcano erupted spectacularly in January 2022. The experimental protocol that I designed to put the models into unfamiliar territory paid off, revealing more intermodel differences and their causes. The last chapter of this thesis contains the preliminary Tonga-MIP results and detailed analysis in preparation for journal submission.