Speaker: Margot Clyne, University of Colorado Boulder

Title: Volcanic eruptions in Global Climate Models

Abstract: Adding the effects of large volcanic eruptions, which cool down the Earth’s surface, to climate models may seem like a straightforward procedure, but it is not. Early versions of volcano-climate modeling made use of available observations and modeling capabilities at hand and successfully established the basics. However, since then, there has been a wide spectrum in how far models have advanced, and in different areas. Even the most simplified volcano models still have their uses in situations when lower levels of accuracy are sufficient to answer the research question or when the event is similar to the volcanoes that the model’s parameterizations had been based on (usually Pinatubo, Chichon, and Agung). Models cannot be properly adaptive to the variety of real-life scenarios unless they are fully equipped with the highest functioning chemistry and physics that do not rely on over-parameterizations whose consequences are not fully understood. Model validation is imprecise, as even the most observable volcanic eruptions still have a range of plausible initial values that models can choose from to start the volcanic injection. Moreover, the relative comparison of different models can be misleading due to the large number of models that now approach the volcano problem at various complexities in contrasting areas. But, if applied in solar geoengineering studies, it is of utmost importance that the models get things right.

In this talk, I will step through the mechanisms at play when volcanic eruptions inject stratospheric SO2, detail how volcanoes are implemented in the most advanced interactive stratospheric aerosol chemistry climate models, and provide guidelines on how to interpret results when things are parameterized in different parts of the process. This will be a deep dive into topics of atmospheric radiation and aerosol optics, aerosol microphysics, stratospheric chemistry, and more. Additionally, I will highlight some areas found in classic volcano parameterizations that could behave differently in solar geoengineering.

 

Bio: Margot Clyne is an atmospheric scientist well known in the volcano-climate interaction community. Volcanoes are a source of natural cooling, and specifying their impacts is important for reducing climate forcing uncertainty. In 2016, motivated by the potential to help improve climate models to reduce skepticism and give further evidence to policymakers that scientists are right about anthropogenic global warming, Clyne approached NCAR scientists and asked how she could help on the “volcano problem”. She had entered at a time when the “volcano problem” was a hot topic for climate modelers, and early results from the Model Intercomparison Project on the climatic response to Volcanic Forcing’s pre study on the 1815 Mt Tambora eruption had just come in. But there was a problem: All of the models disagreed. Clyne figured out why, and what needed to be done. Her 2021 paper “Model physics and chemistry causing intermodal disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble” in the Journal of Atmospheric Chemistry and Physics was selected as a peer reviewed highlight paper by the European Geophysical Union. Clyne pinpointed model development requirements in aerosol microphysics, sulfur chemistry, and more – prompting multiple agencies to make changes to their models.

Clyne is nearing the end of her PhD at the University of Colorado Boulder’s ATOC/LASP under the mentorship of highly acclaimed atmospheric scientist Owen B. Toon. Clyne’s collaborations with multiple co-authors from top modeling institutions work well with her no-stone-left-unturned approach to science, as she is pushed to provide enough evidence that everyone can agree upon. She is a talented communicator and has presented her research at numerous conferences and events. She is now leading the Hunga Tonga-Hunga Ha’apai Volcano Model Intercomparison Project (Tonga-MIP), which she created with the goal of forming a baseline standard for the volcano and climate modeling community, and will be a contributor to the SPARC-HT activity.