Is climate change to blame for the increasing number of seasonal wildfires in California? A new study says in most cases, yes.
A new study that analyzed a multitude of factors that promote wildfire and concludes that “in many, though not all, cases, warming climate is the decisive drive.”
Increasing heat seems to be to blame, especially in the disastrous summer wildfires in the North Coast and Sierra Nevada regions. Temperatures in California have risen 3.25 degrees Fahrenheit since 1986, three-quarters of the increase has happened just since the 1970s. The increasing temperature has led to a fivefold increase in annual burn area and a eightfold increase in summer forest fires.
Researchers warn that the rate of warming is exponential, “meaning that warming has grown increasingly impactful.”
Summer fires are driven by heat and therefore are particularly affected by rising temperatures from global warming. When the air heats up it causes moisture to evaporate from soils and vegetation, meaning fires start more easily.
Climate change may not be contributing as severely to fires in the fall as different variables, such as wind and precipitation, come into play. But researchers say that even large fall fires are likely to become increasingly frequent with continued warming and possible declines in precipitation.
“Anthropogenic warming very likely increased summer forest fire by drying fuels. This trend is likely to continue,” concludes the study.
“It’s not a surprise to see that climate has this effect in forests, but California is so big and so variable, there is no one-size-fits-all explanation for how climate might affect wildfires across the board,” said the study’s lead author, bioclimatologist Park Williams, a bioclimatologist.
Williams previously coauthored a study in 2016 that showed similar findings: that heightened temperatures have doubled the area burned in forest fires in areas of the U.S. West in the past several decades.
Researchers conducting the study used data from a variety of sources going as far back as 100 years. According to the data, the last two years have seen several new wildfire records. In 2017 the state record for the largest individual wildfire (burning 285,000 acres and the most destructive (burning over 5,000 structures and killing 22 people) wildfire was set. Then came 2018 where both of the 2017 records were broken with the biggest individual fire burned over 460,000 acres and the most destructive fire (The Camp Fire) burned nearly 19,000 structures and killed 85 people. Also in 2018 the record was set for the total annual area burned at 1.7 million acres.
As human infrastructure expands in California the chances of human-caused fires increases.
“A century of efforts to suppress virtually all fires has led to a buildup of flammable materials in many forests,” said the Earth Institute at Columbia University. Still, so confounding factors shift fire risk all over the places. Human intrusion in some cases limits the spread of fires and precipitations caries from year to year, adding and subtracting fire risk.