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Speaker: Danielle Touma, Postdoctoral Fellow, National Center for Atmospheric Research

Host: Geeta Persad

Title: Human-driven changes in the characteristics and connectivity of extreme climate events

Abstract: Anthropogenic activities, such as greenhouse gas and aerosol emissions, have altered the spatial and temporal characteristics of extreme climate events and modified their impacts upon human and natural systems. My research seeks to leverage a multitude of regional and global climate datasets—some derived from direct observations, others through numerical modeling—to investigate spatiotemporal variations in extreme precipitation, drought, and wildfire. My overarching goal is to advance our understanding of the mechanisms in which anthropogenic activities impact the climate system, and the subsequent damages incurred by societies and ecosystems.

First, I will present a comprehensive assessment of Atlantic tropical cyclone precipitation using a novel geostatistical framework to analyze in situ measurements over the 20th century. I show that the intensity and spatial extent of precipitation is greatest for major hurricanes after they have weakened to tropical storms, and that the intensity of this rainfall has increased in more recent years. Next, using large-ensemble global climate model experiments, I will show that historical greenhouse gas emissions have increased the risk of extreme fire weather in many regions, and will continue to do so throughout the 21st century. While aerosols have generally reduced the risk of extreme fire weather in the recent past, my research suggests that they are less likely to do so in the future. Using the same large ensemble framework, I will then show that 21st century increases in both extreme fire weather and extreme rainfall frequencies in the western United States lead to greater post-fire hydrologic risks, such as debris flows and flash floods.

Lastly, I will present future research directions, including investigating the changes in the spatiotemporal connectivity of droughts, wildfires and extreme rainfall, and their impacts on regional and global systems. Collectively, my research methods and findings allow a unique understanding of the historical and future changes in extreme climate events, and provide key insight for the management of flood, drought, and wildfire risk.