Warming due to increasing greenhouse gas emissions will likely increase the potential for ‘very large fires’—the top 10 percent of fires, which account for a majority of burned areas in many regions of the United States. Climate change is expected to both intensify fire-friendly weather conditions, as well as lengthen the season during which very large fires tend to spread.
The potential for very large fire events is also expected to increase along the southern coastline and in the forests around the Great Lakes, although the number of events along the northern tier of the country should only increase moderately given the historically low potential for these events.
For this study, researchers considered the average results of 17 climate model simulations to examine how the potential for very large fires is expected to change. Future projections* were based on a higher-emissions scenario called RCP 8.5, which assumes continued increases in carbon dioxide emissions.
Along with the elevated potential for very large fires across the western US in future decades, other climate modeling studies have projected increases in fire danger and temperature, and decreased precipitation and relative humidity during the fire season. The increased potential for these extreme events is also consistent with an observed increase in the number of very large fires in recent decades.
In addition, scientists have detected trends toward overall warming, more frequent heat waves, and diminished soil moisture during the dry season. The combination of these climate conditions and historic fire suppression practices that have led to the build-up of flammable debris have likely led to more frequent large fire events.
At this very moment, more than 70 wildfires are burning throughout the West, putting homes, lives, and livelihoods at risk. The smoke created by these fires exacerbates chronic heart and lung diseases while also degrading visibility and altering snowmelt, precipitation patterns, water quality, and soil properties. In addition to public health impacts, projected trends in extreme fire events have important implications for terrestrial carbon emissions and ecosystems.
The authors of the study also note that these findings could place a burden on national and regional resources for fighting fires. Fire suppression costs in the U.S. have more than doubled in recent decades, exceeding $1 billion per year since the year 2000, the National Interagency Fire Center reports. The vast majority of that money is spent on large incidents.
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