PhD Oral Exam - Travis R. Moore, Geography, Urban & Environmental Studies

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Heavy to extreme precipitation events are often-destructive forms of weather that, despite their infrequency, can lead to significant losses of human life and infrastructural damage. Such events are expected to increase in a warmer world as cumulative carbon emissions continue to rise. However, the extent to which this increase occurs varies considerably across scenarios and spatial scales, especially for the most extreme precipitation. The Transient Response to Cumulative CO2 Emissions (TCRE) has proven to be a powerful metric that characterizes the linear response of global mean temperature to cumulative carbon emissions, and previous research has shown its potential applicability to other climate indicators, such as regional temperature and precipitation, and heat extremes. Using simulations from nine Coupled Model Intercomparison Project Phase 5 (CMIP5) models, the objectives of this dissertation are to quantify extreme precipitation indices of one-day maximum (Rx1day) and five-day maximum (Rx5day) events against cumulative CO2 emissions. I show that the TCRE framework can be applied to represent changes in these precipitation extremes, with validation of this approach at sub-global scales across emissions scenarios. In Chapter 3, I determine whether precipitation extremes respond linearly to cumulative CO2 emissions, at global to local scales, using simple linear regression modelling. In Chapter 4, I conduct a Generalized Extreme Value (GEV) analysis to model the behavior of the most extreme values of Rx1day and Rx5day and evaluate whether trends in location parameter estimates and specified return levels can be approximated by (regional) TCRE values. For Chapter 5, I extend this analysis to estimate remaining carbon budgets (RCBs) associated with avoiding particular extreme precipitation levels. Overall, my results suggest that extreme precipitation work well within a TCRE framework, and that global and sub-global changes can be well approximated by linear responses to cumulative CO2 emissions, though with less robustly linear trends at local scales. My results further highlight that location parameter estimates and return levels of Rx1day and Rx5day scale approximately linearly to increasing cumulative carbon emissions. My findings also show that RCBs are generally small to avoid specified present-day 20-year and 100-year return levels, becoming commonplace events with global warming.