Jul 15, 2019
Observed impacts of anthropogenic climate change on wildfire in California
by
,
Earth's Future
- States that recent fire seasons have fueled intense speculation regarding the effect of anthropogenic climate change on wildfire in western North America, and especially in California
- States that during 1972–2018, California experienced a five‐fold increase in annual burned area, mainly due to more than an eight‐fold increase in summer forest‐fire extent
- States that increased summer forest‐fire area very likely occurred due to increased atmospheric aridity caused by warming
- States that since the early 1970s, warm‐season days warmed by approximately 1.4°C as part of a centennial warming trend, significantly increasing the atmospheric vapor pressure deficit (VPD)
- These trends were consistent with anthropogenic trends simulated by climate models
- Finds that the response of summer forest‐fire area to VPD is exponential, meaning that warming has grown increasingly impactful
- Robust interannual relationships between VPD and summer forest burned area strongly suggest that nearly all of the increase in summer forest‐fire area during 1972–2018 was driven by increased VPD
- Climate‐change effects on summer wildfire were less evident in non‐forest
- Finds that, in fall, wind events and delayed onset of winter precipitation are the dominant promoters of wildfire
- Finds that, while these variables did not change much over the past century, background warming and consequent fuel drying is increasingly enhancing the potential for large fall wildfires
- Among the many processes important to California's diverse fire regimes, warming‐driven fuel drying is the clearest link between anthropogenic climate change and increased California wildfire activity to date