Exploring the Limits of Geophysical Models of Solar Geoengineering

Abstract

Solar Radiation Modification (SRM) is a proposed method of reducing climate risks associated with climate change via modification of Earth's radiative budget. Due to the impracticality of global experimentation, research on SRM has largely been conducted via computational simulations of the Earth system. These simulations may incorporate different spatial scales, physical capabilities or relevant chemistry dependent on the type and version of the model used. Computational tractability inhibits any single model from perfectly capturing all relevant phenomena. Therefore to produce a robust understanding of SRM a diverse set of models must be applied. This thesis leverages three distinct types of models to explore key uncertainties related to the efficacy of SRM. In the first part of this thesis we explore the microphysical limitations of aerosol injection relevant to a small scale stratospheric aerosol injection (SAI) experiment. We detail the configuration of a novel plume scale model which we use to quantify the influence of injection material, mass flux and configuration. Findings indicate that the plumes downstream aerosol size distribution depends more strongly on injection rate than injection configuration. The second part of this thesis outlines the potential role for super-parameterized general circulation models as a means of evaluating standard model ability to capture SRM induced changes to vertical heating distributions and modifications to convection. The third part of this thesis shows results from a five model intercomparison with an imposed stratospheric heating tendency and evaluates policy relevant surface variables for robust responses to the applied forcing. Results suggest that previous estimations of the overall role of stratospheric heating in driving SRM surface response were overstated, and provides a framing to contextualize explicitly derived modes of aerosol forcing in the overall short wave radiative reduction. This thesis concludes with a reflection on the role of climate grief in research and discourse on climate change and SRM.