Democratic Gov. Jerry Brown called wildfires ripping through Southern California part of the “new normal,” and The New York Times said the state was in for “a future with more fire” because of global warming.
Sounds terrifying, but it’s just not backed up with the weight of scientific evidence, according to Cliff Mass, a climate scientist at the University of Washington.
“Those that are claiming the global warming is having an impact are doing so either out of ignorance or their wish to use coastal wildfires for their own purposes,” Mass wrote of the wildfires on his blog.
“Wildfires are not a global warming issue, but a sustainable and resilience issue that our society, on both sides of the political spectrum, must deal with,” Mass wrote on Sunday.
Wildfires have scorched large swaths of Southern California, forcing thousands to flee and destroying hundreds of structures. Politicians and some news outlets have tied the fires to man-made global warming.
“With climate change, some scientists are saying that Southern California is literally burning up,” Brown said on Saturday. “So we have to have the resources to combat the fires and we also have to invest in managing the vegetation and forests … in a place that’s getting hotter.”
Mass, however, wrote that “there is no credible evidence that global warming is causing an increase currently or will increase in the future of the number or intensity of wildfires over coastal California from San Diego to the [San Francisco] Bay region.”
“A reading of the peer-reviewed literature on California fires and an examination of observations and prior climate information can easily show that these claims are baseless, if not outright wrong,” Mass wrote, pointing to several sources.
The latest National Climate Assessment report gave the connection between global warming and western wildfires a “low” to “medium” confidence rating and even presented evidence showing a decrease in large wildfires across Mediterranean California.
Based on the peer-reviewed evidence, Mass said other factors, like “prior fire suppression, irresponsible expansion of homes, the influx of invasive grasses” have only exacerbated wildfires in the Golden State.
California has a long history of wildfires sparking late in the year. This year, heavy winter rainfall spurred plant growth, which dried out in summer and provided an abundance of fuel for fires — most of which are man-made.
“Coastal California has dry summers because the jet stream goes far north during the warm season and they don’t have many thunderstorms because of the relatively cool Pacific,” Mass wrote. “So grasses, shrubs, and other fuels will be dry by the end of summer and during fall, no matter what.”
“So even if the summer/fall temperatures rose and the conditions dried further under global warming, IT WOULD NOT MATTER,” Mass wrote. “Without any additional warming, the fuels in late summer and fall are dry enough to burn over coastal California and always have been.”
Brown, among others, argue global warming is delaying rainfall that generally comes in the fall, contributing to longer fire seasons. Mass contested this argument.
“First, there is no trend in late fall (October to December) precipitation over the southern CA coastal zone,” Mass wrote. “And in any case, southern CA climatologically gets very little precipitation during the fall — and this the impacts are minor.”
Mass also looked at the literature on the Santa Ana winds, the strong, dry offshore winds that often accompany devastating wildfires. Mass found that global warming is actually expected to weaken, not strengthen, Santa Ana winds.
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