Changes to tornado outbreaks under anthropogenic climate change in the contiguous United States

Abstract

As climate change progresses, understanding the atmospheric conditions that support tornado outbreaks—and how these conditions might shift in a warmer climate—is essential for future preparedness. However, tornado outbreaks present unique challenges for global climate models due to their small-scale and transient nature. The goal of this dissertation is to explore tornado outbreak environments through the identification of dominant atmospheric patterns associated with them and to assess the ability of a global climate model to simulate and project these environments under future scenarios. The study begins with maximum covariance analysis applied to the 5th version of European Centre for Medium-Range Weather Forecasts reanalysis (ERA5) dataset to identify atmospheric patterns associated with major tornado outbreaks in the United States, focusing on May outbreaks from 1950 to 2019. Based on this analysis, a threshold-based filtering technique is developed to approximate outbreak-supportive environments in climate model simulations. This method is first applied to historical simulations from the MPI-ESM1.2-HR global climate model to evaluate the model’s ability to reproduce the dominant pattern associated with major tornado outbreaks. Finally, this approach is extended to future climate projections (2065–2100) under multiple greenhouse gas emission scenarios to explore potential shifts in the frequency and spatial distribution of these environments. The findings of this research suggest that climate change is expected to influence the characteristics of tornado outbreak environments, with variations across different emission scenarios. This study offers a foundation for future research on climate-change impacts on mid-latitude, mesoscale severe weather events and provides preliminary insights into how tornado-supportive environments could evolve, contributing to a more targeted approach for examining tornado outbreak risks in a warming world.