Wildfire climate connection

An early photo of a huge smoke cloud from the Bootleg wildfire in Oregon. July 17, 2021.
An early photo of a huge smoke cloud from the Bootleg wildfire in Oregon. July 17, 2021. (InciWeb via inciweb.nwcg.gov)

Climate change, including increased heat, extended drought, and a thirsty atmosphere, has been a key driver in increasing the risk and extent of wildfires in the western United States during the last two decades. Wildfires require the alignment of a number of factors, including temperature, humidity, and the lack of moisture in fuels, such as trees, shrubs, grasses, and forest debris. All these factors have strong direct or indirect ties to climate variability and climate change. A 2016 study found enhanced the drying of organic matter and doubled the number of large fires between 1984 and 2015 offsite link in the western United States. A 2021 study supported by NOAA concluded that climate change has been the main driver of the increase in fire weather offsite link in the western United States.

Drought and persistent heat set the stage for extraordinary wildfire seasons from 2020 to 2022 across many western states, with all three years far surpassing the average of 1.2 million acres burned since 2016. Extreme fire behavior during this period shocked many wildfire managers, as several huge blazes burned for months, others incinerated entire communities, and still others erupted during nighttime wind events, when firefighters could normally count on working the fire line. In the Sierras of California and the Rocky Mountains of Colorado, flame fronts threw embers over the crests of mountain divides, across miles of rocky and inflammable terrain, one more behavior never before observed by wildfire managers.

Research shows that changes in climate create warmer, drier conditions, leading to longer and more active fire seasons. Increases in temperatures and the thirst of the atmosphere due to human--caused climate change have increased aridity of forest fuels during the fire season. These drivers were found to be responsible for over half the observed decrease in the moisture content of fuels in western U.S. forests from 1979 to 2015, and the doubling of forest fire burned area over the period 1984–2015. For much of the U.S. West, projections show offsite link that an average annual 1 degree C temperature increase would increase the median burned area per year by as much as 600 % offsite link in some types of forests. In the Southeastern United States modeling suggests increased fire risk and a longer fire season, with at least a 30 percent increase from 2011 in the area burned by lightning-ignited wildfire by 2060.

An early photo of a huge smoke cloud from the Bootleg wildfire in Oregon. July 17, 2021.
An early photo of a huge smoke cloud from the Bootleg wildfire in Oregon. July 17, 2021. (InciWeb via inciweb.nwcg.gov)