In the second report of its “Wake Up Call” series on global warming’s worsening of extreme weather, the National Wildlife Federation describes how the western United States has entered a new era of catastrophic wildfires, brought on by global warming, past forest management, and poor land development.
The frequency of large wildfires and the total area burned have been steadily increasing in the Western United States. Warmer springs and longer summer dry periods since the mid-1980s are linked to a four-fold increase in the number of major wildfires each year and a six-fold increase in the area of forest burned compared with the period between 1970 and 1986. The fire season stretches about 78 days longer and individual fires last about 30 days longer.
In a video, the National Wildlife Federation’s climate scientist, Amanda Staudt, describes how “global warming will increase the risk of wildfires.” Watch it:
Global warming increases wildfire risk in several ways. From the report, Increased Risk of Catastrophic Wildfires: Global Warming’s Wake-Up Call for the Western United States:
— Longer fire seasons will result as spring runoff occurs earlier, summer heat builds up more quickly, and warm conditions extend further into fall. Western forests typically become combustible within a month of when snowmelt finishes. Snowpack is now melting 1 to 4 weeks earlier than it did 50 years ago.
— Drier conditions will increase the probability of fire occurrence. Summertime temperatures in western North America are projected to be 3.6 to 9 degrees Fahrenheit higher by mid-century, enhancing evaporation rates, while precipitation is expected to decrease by up to 15 percent.
— More fuel for forest fires will become available because warmer and drier conditions are conducive to widespread beetle and other insect infestations, resulting in broad ranges of dead and highly combustible trees. Higher temperatures enhance winter survival of mountain pine beetles and allow for a more rapid lifecycle. At the same time, moderate drought conditions for a year or longer can weaken trees, allowing bark beetles to overcome the trees’ defense mechanisms more easily.
— Increased frequency of lightning is expected as thunderstorms become more severe. In the western United States a 1.8 degree Fahrenheit increase in temperature is expected to lead to a 6 percent increase in lightning. This means that lightning in the region could increase by 12 to 30 percent by mid-century.
Not only is global warming worsening wildfires (despite Joel Achenbach’s protestations), but catastrophic wildfires are hastening global warming, by rapidly releasing carbon it took the forests decades, even centuries, to store:
In recent years, fires in the western United States have released carbon dioxide into the atmosphere equivalent to about 11 percent of their annual fossil fuel emissions. In some Western states a fire spanning over just a couple months can emit nearly as much carbon dioxide as its total annual fossil fuel emissions.
This vicious cycle is one of many dangerous experiments humanity is running on its only planet through unmoderated pollution. Recent scientific reports have discussed how oceanic dead zones caused by fertilizer runoff and air pollution have reached catastrophic levels. Atmospheric oxygen is declining, reaching hazardous lows in urban centers. And rapidly declining arctic sea ice is leading to permafrost melt, which has kept frozen thirty percent of all soil-based carbon for hundreds of thousands of years.