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.
California has experienced increasingly severe autumn wildfires over the past several decades, which have exacted a rising human and environmental toll. Recent fire and climate science research has demonstrated a clear link between worsening California wildfires and climate change, mainly though the vegetation‐drying effect of rising temperatures and shifting precipitation seasonality. New work by Luković et al. (2021) explores observed changes in California's autumn precipitation in greater detail, finding that the rainy season has indeed become progressively delayed and that the “sharpness” of California precipitation seasonality has increased. These precipitation shifts have important implications for the region's ecology and wildfire risk, as they increase the degree of temporal overlap between extremely dry vegetation conditions and fire‐promoting downslope winds in late autumn. Both of these observed shifts are consistent with climate model projections for the region's future, suggesting that recent trends may offer an early preview of larger changes to come.
more » « less- PAR ID:
- 10367086
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 48
- Issue:
- 5
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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