Department Seminar: Meiyun Lin

Title: Earth System Feedbacks to Air Quality Extremes in a Changing Climate

Abstract: With rising temperatures and shifting rainfall patterns, compound drought and heatwaves are increasing in frequency and intensity. Lin will discuss how atmosphere-biosphere interactions and Earth system feedbacks (e.g., changes in ozone removal by vegetation, wildfires, and BVOC emissions) during compound drought and heatwaves exacerbate air pollution extremes in a changing climate. Using six decades of observations and Earth system model simulations (1960-2018), her work highlights an underappreciated ‘climate penalty’ feedback mechanism – namely, substantial reductions of ozone uptake by drought-stressed vegetation – as a missing piece to the puzzle of why European ozone pollution episodes have not decreased in recent decades, despite marked reductions in regional emissions of ozone precursors due to regulatory changes. Her research is finding that severe drought stress can cause 50-70% reductions in ozone removal by vegetation, leading to a three-fold increase in  high-ozone pollution events during recent historic heatwaves in Europe, North America and East Asia. She also will explore how increasing wildfires under different climate change scenarios impact Western U.S. fine particulate pollution over the course of 21st century. The consequential events like the 2020 wildfire season over the western U.S. could recur every 3 to 5 years in the late 21st century under low-mitigation climate scenarios. Finally, she will discuss opportunities and challenges in understanding Earth system feedbacks to air quality in a warming climate, including observation needs and new tools such as variable-resolution chemistry-climate models with regional grid refinement.