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Large role of anthropogenic climate change in driving smoke concentrations across the western United States from 1992 to 2020.

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Bibliographic Details
Title: Large role of anthropogenic climate change in driving smoke concentrations across the western United States from 1992 to 2020.
Authors: Feng X; John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138., Mickley LJ; John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138., Kaplan JO; Department of Earth, Energy, and Environment, University of Calgary, Calgary, AB T2N 1N4, Canada., Kelp M; Department of Earth System Science, Doerr School of Sustainability, Stanford University, Stanford, CA 94305., Li Y; Department of Environmental Science, Baylor University, Waco, TX 76798., Liu T; Department of Geography, University of British Columbia, Vancouver, BC V6T 1Z2, Canada.
Source: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2025 Dec 09; Vol. 122 (49), pp. e2421903122. Date of Electronic Publication: 2025 Dec 02.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: National Academy of Sciences Country of Publication: United States NLM ID: 7505876 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1091-6490 (Electronic) Linking ISSN: 00278424 NLM ISO Abbreviation: Proc Natl Acad Sci U S A Subsets: MEDLINE
Imprint Name(s): Original Publication: Washington, DC : National Academy of Sciences
MeSH Terms: Climate Change* , Wildfires* , Smoke*/analysis , Air Pollutants*/analysis , Air Pollution*/analysis , Anthropogenic Effects*, Humans ; United States ; Particulate Matter/analysis ; Environmental Monitoring
Abstract: Competing Interests: Competing interests statement:The authors declare no competing interest.
Wildfire activity has increased dramatically in the western United States over the last three decades, having a significant impact on air quality and human health. However, quantifying the drivers of trends in wildfires and subsequent smoke concentrations is challenging, as both natural variability (NV) and anthropogenic climate change (ACC) play important roles. Here, we devise an approach involving observed meteorology and vegetation and a range of models to determine the relative roles of ACC and NV in driving burned area across the western United States. We also examine the influence of ACC on smoke concentrations. We estimate that ACC accounts for 33 to 82% of observed total burned area, depending on the ecoregion, yielding 65% of total fire emissions on average across the western United States from 1992 to 2020. In all ecoregions except Mediterranean California, ACC contributes to a greater percentage of burned area in lightning-ignited wildfires than in human-ignited wildfires. On average, ACC contributes 49% to smoke PM 2.5 concentrations in the western United States from 1997 to 2020, and explains 58% of the increasing trend in smoke PM 2.5 from 2010 to 2020. Northern California and areas in Oregon, Washington, and Idaho experience the greatest smoke concentrations attributable to ACC, averaging 40 to 66% of total PM 2.5 over 2010-2020. Our work highlights the significant role of ACC in degrading air quality in the western United States and identifies those regions most vulnerable to wildfire smoke and thus adverse health impacts.
Grant Information: NA22OAR4310140 DOC | NOAA | Climate Program Office (CPO)
Contributed Indexing: Keywords: anthropogenic climate change; smoke concentrations; wildfires
Substance Nomenclature: 0 (Smoke)
0 (Air Pollutants)
0 (Particulate Matter)
Entry Date(s): Date Created: 20251202 Date Completed: 20251202 Latest Revision: 20251202
Update Code: 20251203
DOI: 10.1073/pnas.2421903122
PMID: 41329743
Database: MEDLINE
Description
Abstract:Competing Interests: Competing interests statement:The authors declare no competing interest.<br />Wildfire activity has increased dramatically in the western United States over the last three decades, having a significant impact on air quality and human health. However, quantifying the drivers of trends in wildfires and subsequent smoke concentrations is challenging, as both natural variability (NV) and anthropogenic climate change (ACC) play important roles. Here, we devise an approach involving observed meteorology and vegetation and a range of models to determine the relative roles of ACC and NV in driving burned area across the western United States. We also examine the influence of ACC on smoke concentrations. We estimate that ACC accounts for 33 to 82% of observed total burned area, depending on the ecoregion, yielding 65% of total fire emissions on average across the western United States from 1992 to 2020. In all ecoregions except Mediterranean California, ACC contributes to a greater percentage of burned area in lightning-ignited wildfires than in human-ignited wildfires. On average, ACC contributes 49% to smoke PM <subscript>2.5</subscript> concentrations in the western United States from 1997 to 2020, and explains 58% of the increasing trend in smoke PM <subscript>2.5</subscript> from 2010 to 2020. Northern California and areas in Oregon, Washington, and Idaho experience the greatest smoke concentrations attributable to ACC, averaging 40 to 66% of total PM <subscript>2.5</subscript> over 2010-2020. Our work highlights the significant role of ACC in degrading air quality in the western United States and identifies those regions most vulnerable to wildfire smoke and thus adverse health impacts.
ISSN:1091-6490
DOI:10.1073/pnas.2421903122