Although wildfire is part of the natural ecosystem cycle over the western U.S., its intensity and frequency has been increasing at an alarming rate in recent decades. A new study shows that climate change is the main driver of this increase in fire weather in the western United States. And even though wetter and cooler conditions could offer brief respites, more intense and frequent wildfires and aridification in the western states will continue with rising temperatures.
In the study, researchers with the University of California, Los Angeles found that the leading cause of the rapid increase of wildfires over the western U.S. is the rapid increase in surface air vapor pressure deficit or VPD, a measure of how thirsty the atmosphere is. The warming of surface temperature contributed 80% of the VPD increase across the western U.S. between 1979-2020. Only 32% of the increase in VPD was caused by changes in weather patterns, which is mostly due to natural climate variability. The remaining 68% of the increase in VPD is explained by human-caused global warming. This study is part of NOAA’s Drought Task Force IV research funded by NIDIS through NOAA’s Climate Program Office Modeling, Analysis, Predictions and Projections Program.
This study also shows that western United States has passed a critical threshold since about 2000, and human-caused climate change is now the dominant contributor to the increase of wildfire risk. It also suggests that the increase of VPD since 2000 is dominated by aridification due to climate change. Thus, even though wetter and cooler conditions could offer brief respites, VPD will continue increasing, leading to more intense and more frequent wildfires and aridification in the western states overall.