Wildfires in California: Yup, this is the New Normal

Without a doubt, the 2017 and 2018 fire seasons in California are historically unprecedented. The last two fire seasons account for the top three most destructive wildfires in the state’s history. As California Governor Jerry Brown stated at a press conference in December 2017, “We’re facing a new reality in this state.”

The number of homes destroyed, the tragic loss of life and the unanticipated extremity of wildfire behavior have made it hard to overstate how different these fire seasons have been from the previously assumed norm. How do these wildfire losses fit into recent trends? And what do these new record losses mean for insurers?

In order to grasp the scale of the destruction, let’s look at how California’s wildfire losses over the last two years stack up with previous wildfire events in the state:

These losses are not only spiking in an alarming way, but look very much like a new trend. What’s going on?

There are a number of factors leading to more severe wildfires, and most of them are not surprising. Record temperatures are drying out the accumulated fuel load across the state. There’s also been a long-term trend over the last fifty years of homeowners putting themselves into harm’s way– more and more homes have been built in the wildland-urban interface (WUI) where development encroaches into wilderness areas, which often have high brush hazards. Since the late 1970s, the number of Americans living in WUI lands has doubled, and 60 percent of new U.S. homes have been built on WUI lands since 1990.

But of all the various factors that impact wildfire risk, our models show that the biggest driver of the new fire behavior is the lengthening fire season. As we see wildfire losses spiking, we’re also seeing them occurring later in the year. “Fires in the winter months are uncommon,” Chief Daniel Berlant, assistant deputy director of Cal Fire, told the New York Times. “But in the last decade we’ve had more and more fires in the nontraditional fire season months, which really emphasizes the changing climate that we have here in California.” Kevin Trenberth, a climate scientist in the climate analysis section of the National Center for Atmospheric Research, agrees: “In the West, they used to talk about a fire season,” he told Inside Climate News. “The fire season used to be 60 days, then 90 days, and now they think it’s year-round. There’s no pause.”

This change in the length of the California fire season is key to understanding the new wildfire behavior. The scientists at Delos are leading experts in modeling the variables that are predictive of wildfire risk, and our models show that the lengthening fire season leads to a surprisingly large impact. This is because of how the basic ingredients for wildfire change throughout the year, and how the combine together in non-linear ways.

Unfortunately, the longer fire seasons that we’ve been experiencing are not an anomaly. Climate scientists have predicted this exact outcome, and the lengthening dry season averages will become even more extreme over the next decades.

Shifts in precipitation seasonality. Relative changes in monthly mean precipitation at the end of the twenty-first century (2070–2100) as a percent of the historical baseline, for a range of latitudes spanning the California coast. Percentages in the legend denote changes in the ratio between precipitation falling during the core rainy season vs. the marginal rainy season. Dashed black horizontal line denotes zero change in magnitude. (Image source: Daniel L. Swain , Baird Langenbrunner, J. David Neelin, and Alex Hall; https://doi.org/10.1038/s41558-018-0140-y)

 

Delos is preparing for this new reality by modeling how longer fire seasons impact wildfire risks. Other entities are adjusting to the new extreme fire behavior as well: California Department of Forestry and Fire Protection (Cal Fire) released a list of 35 priority fuel-reduction projects it wants to start immediately across the state over roughly 90,000 acres. That’s double the acreage the agency aimed to cover in the current fiscal year, Cal Fire Deputy Chief Scott McLean said. Another solution that offers to make a large impact is the state’s Public Safety Power Shutoff program, developed in cooperation with state utility regulators at the Public Utilities Commission. The program aims to shut off power in wildfire risk areas during elevated ignition risk conditions, such as high winds or temperature. 

But these solutions can only do so much. They address fuel and ignition, but fire weather is also a major driver. And Californians must adjust to the reality that the severity of fire weather is worsening, particularly due to the lengthening fire season, and that it will continue to do so. 

Shanna McIntyre, Chief Data Officer, DelosWildfires in California: Yup, this is the New Normal

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