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Warming weakens the night-time barrier to global fire
Jennifer K Balch1,2, John T Abatzoglou3, Maxwell B Joseph4,5
1Earth Lab, CIRES, University of Colorado Boulder, Boulder, CO, USA. jennifer.balch@colorado.edu.
Wildfires are intensifying at night due to hotter, drier conditions, reducing crucial fire suppression opportunities. This trend is linked to climate change, leading to longer and larger fires.
Area of Science:
- Environmental Science
- Climate Science
- Fire Ecology
Background:
- Nighttime traditionally offers reduced fire risk due to lower temperatures and vapor pressure deficit (VPD).
- Current fire danger assessments primarily focus on daytime conditions, overlooking nighttime fire behavior.
- The impact of changing nighttime climate conditions on fire intensity is not well understood.
Purpose of the Study:
- To investigate the changes in nighttime fire intensity and its relationship with climatic conditions.
- To analyze global trends in nighttime flammability and its duration.
- To assess the role of anthropogenic climate change in exacerbating nighttime fire conditions.
Main Methods:
- Utilized global satellite observations of daytime and nighttime fire detections from 1979-2020.
- Correlated fire data with hourly climate data to determine landcover-specific VPD thresholds (VPDt).
- Analyzed trends in daily minimum VPD, nighttime flammability hours, and nighttime fire intensity.
Main Results:
- Global daily minimum VPD increased by 25% from 1979-2020.
- Flammable nighttime hours (VPD > VPDt) increased by 110 hours annually across burnable lands.
- Nighttime fire intensity increased by 7.2% globally from 2003-2020, with some areas experiencing over a week more flammable nights.
Conclusions:
- Hotter and drier nights are increasing nighttime fire intensity, diminishing natural fire suppression opportunities.
- Increased nighttime flammability, driven by climate change, contributes to more intense, longer-lasting, and larger wildfires.
- Findings highlight the urgent need to consider nighttime conditions in wildfire management and climate change adaptation strategies.
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