The discussion featured Daniel Swain, a UCLA climate scientist known as "Weather West," and Mark Brown, executive director of the Marin Wildfire Authority.
Marin County is lucky to have evaded catastrophic wildfires and floods that have devastated parts of California, a well-known climate scientist said this week.
Daniel Swain, a UCLA scientist popularly known as “Weather West,” appeared Wednesday at a talk held by the Ecologically Sound Practices Partnership, a collaboration among Marin fire authorities and environmental organizations.
Swain, a San Rafael High School graduate, and Mark Brown, executive director of the Marin Wildfire Authority, discussed the effects of climate change on wildfire, specifically in the northern half of the state. The talk was held at the authority’s headquarters in San Rafael.
Swain said California is in an era of “megafire” as climate change pushes an increasingly dramatic swing between drought and rainy years, with “progressively drier and wetter extremes.” Dry, hot conditions are stretching into late autumn, when the state often experiences strong offshore winds, which is of particular concern for Marin, he said.
“Autumn follows summer, and summer is the warm season when we know it hasn’t rained and when vegetation is at it’s driest,” he said. “And so it’s precisely when the vegetation is most flammable that we’re most likely to see wind events that put us in the upper end of the fire weather distribution.
“The risk here is a little more conditional and episodic,” he added. “The very worst plausible risks are super high. We don’t experience them often.”
Because of that, it’s difficult to be prepared for the type of fire that could happen when conditions are primed for disaster, he said.
“The problem isn’t so much what’s happening in the ordinary years, the problem is what’s happening in the extraordinary years,” Swain said.
The discussion happened the same day Gov. Gavin Newsom warned Californians to be alert as the state heads into what could be a worse-than-expected fire season following a brutal heat wave that dried out vegetation and contributed to far more acres burning statewide than normal.
As of Thursday, 3,579 wildfires have burned nearly 220,000 acres across the state this season, according to Cal Fire. One death has been reported and more than 130 structures have been destroyed or damaged.
Swain said there are three main factors that fire frequency and intensity have magnified in recent years.
One is that today, there are more people living in fire-prone areas, increasing the risk of loss if there is a fire. Second, land management and fire suppression policies over 100-plus years led to the elimination of beneficial prescribed burning that was once regularly performed by Indigenous people. The third is that climate change is creating more severe conditions, he said.
In addition to the threat of fire in Marin there is also the flood risk, especially if extreme shifts between wet and dry years persist, Swain said.
The Ross Valley and areas of the Mount Tamalpais watershed are particularly susceptible to flooding, he noted.
As an example, Swain pointed to the devastation left by the Thomas fire that burned more than 281,800 acres and destroyed more than 1,000 structures in Santa Barbara and Ventura counties in December 2017.
After the conflagration burned for about a month, a powerful winter storm loosened the mud and debris in the burn-scarred areas in the Santa Ynez mountains. A landslide pummeled through the town of Montecito, resulting in 23 deaths and the destruction of about 100 homes.
Brown, the former deputy chief of the Marin County Fire Department, was assigned to the incident management team that created the plan to suppress the Thomas fire. He said that at the time, it wasn’t warm, so heat wasn’t a factor in the ignition of the fire. But there were 17 “red flag” fire weather warning days issued by the National Weather Service, and there had been 11 months of no measurable rainfall, which set up the scene for explosive fire conditions, he said.
“It’s not just the back and forth but it’s also intensity that the fires are burning at that makes the soils so much more unstable,” Brown said.
Swain said the geology and geography are different enough in Marin that the debris flow risk is considerably lower.
“But you know, Marin County is at high risk of landslides and mudslides to begin with,” Swain said. “So if there are large fires on steeper slopes, we’re going to see that risk.”
If there is a fire in the Mount Tamalpais watershed, there could be increased risk of flash flooding in the Ross Valley in the winters that follow, Swain said.
Earthquakes are another concern, Swain said.
“If we do get a big earthquake in the fall when it’s dry, the big risk is going to be fire in the Bay Area in general, and in particular in Marin County,” he said.
Swain said the point is not to scare people but “to avert some of those potential future losses that could otherwise occur.”
He encouraged the audience and fire officials to think creatively about vegetation management and fire prevention. He said already MWPA has worked hard to ensure fuel breaks throughout the county.
“Not everything can be prevented, but I think a lot of it can,” he said.
The Bay Area News Group contributed to this report.
