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Abstract Vapor pressure deficit (VPD) is a key fire weather indicator linked to increased burned areas in western US. Despite a strong increase in regional VPD due to climate change, we find no significant trend in VPD on fire ignition days (VPDF). This discrepancy is due to a decreasing climatological mean (VPDF‐m), driven by the expansion of fires into higher‐latitude and higher‐altitude regions with climatologically lower VPD, and a relatively stable anomaly (VPDF‐a). The weak trend in this VPDF‐ais, in turn, a result of two opposing trends: a significant increase in the thermodynamic contribution from background warming, offset by a weakening of the dynamic contribution from circulation patterns. This lowering of the circulation “bar” for ignition, where less extreme weather is now sufficient to start large fires, explains the observed spatial expansion of fire risk, meaning regions historically less prone to fires now face heightened risk.
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This content will become publicly available on February 20, 2027
Increasing synchronicity of global extreme fire weather
Concurrent extreme fire weather creates favorable conditions for widespread large fires, which can complicate the coordination of fire suppression resources and degrade regional air quality. Here, we examine the patterns and trends of intra- and interregional synchronous fire weather (SFW) and explore their links to climate variability and air quality impacts. We find climatologically elevated intraregional SFW in boreal regions, as well as interregional synchronicity among northern temperate and boreal regions. Significant increases in SFW occurred during 1979 to 2024, with more than a twofold increase observed in most regions. We estimate that over half of the observed increase is attributable to anthropogenic climate change. Internal modes of climate variability strongly influence SFW in several regions, including Equatorial Asia, which experiences 43 additional intraregional SFW days during El Niño years. Furthermore, SFW is strongly correlated with regional fire-sourced PM2.5in multiple regions globally. These findings highlight the growing challenges posed by SFW for firefighting coordination and human health.
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- Award ID(s):
- 2019762
- PAR ID:
- 10710917
- Publisher / Repository:
- Science Advances
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 12
- Issue:
- 8
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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