Anthropogenic Influence on Recent Severe Autumn Fire Weather in the West Coast of the United States. Issue 4 (15th February 2022)

• Record Type: Journal Article
• Authors: Hawkins, Linnia R.; Abatzoglou, John T.; Li, Sihan; Rupp, David E.
• Is Part Of: Geophysical research letters. Volume 49:Issue 4(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-15
• Subjects: attribution -- wildfire -- extreme events -- Regional climate modeling -- fire weather; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL095496
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Extreme wind‐driven autumn wildfires are hazardous to life and property, due to their rapid rate of spread. Recent catastrophic autumn wildfires in the western United States co‐occurred with record‐ or near‐record autumn fire weather indices that are a byproduct of extreme fuel dryness and strong offshore dry winds. Here, we use a formal, probabilistic, extreme event attribution analysis to investigate the anthropogenic influence on extreme autumn fire weather in 2017 and 2018. We show that while present‐day anthropogenic climate change has slightly decreased the prevalence of strong offshore downslope winds, it has increased the likelihood of extreme fire weather indices by 40% in areas where recent autumn wind‐driven fires have occurred in northern California and Oregon. The increase was primarily through increased autumn fuel aridity and warmer temperatures during dry wind events. These findings illustrate that anthropogenic climate change is exacerbating autumn fire weather extremes that contribute to high‐impact catastrophic fires in populated regions of the western US. Plain Language Summary: Over the last several years, California and western Oregon have seen their largest and most destructive wildfires on record. The rapid and extensive growth of many of these fires that invaded populated areas was driven by strong, dry, offshore, downslope autumn winds over fuels that had become exceedingly dry over the summer and remained dry into autumn. We used simulations of both the modern‐era climate and a climate that could have been, absent human influence, to investigate the effect of anthropogenic climate change on the likelihood of extreme fire weather conditions (warm, very dry, and very windy) that were present during recent catastrophic wildfires. Despite a small decrease in the frequency of strong offshore winds, anthropogenic climate change has already increased the likelihood of extreme autumn fire weather across most of the west coast of the US through higher temperature and drier fuels, heightening the risk to life and property. Key Points: Anthropogenic climate change has already increased the likelihood of autumn wind‐driven extreme fire weather conditions in the western US Increased autumn fuel aridity and warmer temperatures during dry wind events increased the likelihood of extreme fire weather in 2017 and 2018 indices by 40% Present‐day anthropogenic climate change has slightly decreased the prevalence of strong offshore downslope winds