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The winds in the hills north of Healdsburg hit 93 mph Sunday, spreading huge flames from the Kincade Fire across the rural Sonoma County landscape and forcing the evacuation of more than 185,000 people.
A day later, on Monday, hot Santa Ana winds roaring toward the ocean in Los Angeles reached 66 mph as the Getty Fire threatened houses and freeways.
There is wide agreement among scientists that climate change is making wildfires worse because temperatures are getting hotter, drying out brush, grasses and trees.
But what about the ferocious winds firefighters are dealing with, the Diablo winds in Northern California and Santa Ana winds in Southern California? Are they getting stronger or more frequent because of climate change?
Researchers have been looking at the October winds, searching for trends in this new, warmer era and so far haven’t found a clear connection.
“We have wind records going back to the 1940s,” said Park Williams, a bio-climatologist at Columbia University’s Lamont-Doherty Earth Observatory in New York. “We don’t see any trend one way or another in the frequency or the intensity of these wind events. This year is probably going to go down as a record year, but we don’t see a trend so far.”
Daniel Swain, a climate scientist at UCLA, agreed. But, he said, “While there’s not much evidence at this point of a direct link between climate change and changes in offshore wind patterns, there is evidence that climate trends are increasing the likelihood that such winds coincide with dangerously dry vegetation conditions, leading to increased wildfire risk.”
Winds are hardly the only factor. The Kincade Fire ignited in a combination of dry and windy conditions that occur every October in California. But the risk of sparks from cars, power lines and discarded cigarettes has grown every year, as California’s population increases and more homes are built in rural areas. And PG&E, the area’s largest utility, has failed to keep pace in clearing trees and modernizing its power lines.
Add to that the hotter, drier conditions from climate change, and when fires such as the Kincade Fire start, they can burn more intensely.
“Would this fire have happened if there was no climate change? Probably,” said Paul Ulrich, an associate professor of climate modeling at UC Davis. “But with climate change, you are going to have conditions that are more conducive to larger, more intense fires in the years ahead.”
The Earth is warming. The 10 hottest years back to 1880 when modern temperature records began all have occurred since 1998, according to NASA and NOAA, the parent agency of the National Weather Service. And California’s average summer temperatures have risen 3.25 degrees Fahrenheit since 1896, with three-quarters of that increase coming since 1970.
But scientists say pine forests in the Sierra Nevada and other rural parts of California are different than coastal grass lands and chaparral.
“The effect of climate change on forest fires is straightforward,” Williams said. “As it has gotten warmer, the fires have gotten bigger.”
Williams was a lead author on a study published in July that found from 1972 to 2018, the area burned annually in California has increased fivefold, fueled mainly by a spike in summer forest fires.
In fact, nine of the 10 largest wildfires in California since modern records began in the 1930s have happened since 2000, according to Cal Fire, the state’s primary firefighting agency.
Along with climate change, a century of fire suppression that has built up unnaturally dense and often unhealthy pine and fir forests also is partially to blame.
Simply put, the West is hotter and drier now than it was a generation or two ago. Soils are more arid, and trees and brush have less moisture. One spark has a higher chance of doing immense damage.
Not everywhere is a pine forest, however, and when it comes to oak woodlands or to grassy areas, as in the Sonoma Valley, the picture grows more complex.
The number and size of wildfires depends on a variety of factors, including when the first big rains of the winter season happen; the strength and timing of hot, powerful winds that blow in from the Nevada desert toward the ocean; and the luck — or bad luck — of human causes, from a cigarette thrown out a car window to a power line not attached securely enough to its tower.
Yet in this week’s conflagration, it has been the winds that are remarkable. On Monday, Gov. Gavin Newsom said firefighters had put out more than 330 fires in the past 24 hours around the state. In some places at high elevations, winds exceeded 74 mph — the equivalent of a Category 1 hurricane.
On Saturday, Craig Clements, director of the Fire Weather Research Laboratory at San Jose State University, was in Sonoma County, tracking the Kincade Fire.
He noted that temperatures were not hot, and fuel moisture levels in the Bay Area this year are generally tracking about average for this time of year, in part because the state had a wet winter.
“It was 46 degrees, and I saw flames hundreds of feet high,” Clements said. “The wind was blowing 50 mph. If we didn’t have the wind, we wouldn’t be talking about this. A lot of it is bad luck.”
A paper published earlier this year by scientists at the Scripps Institution of Oceanography suggested that the warming climate might actually cause Santa Ana winds in Southern California to become less frequent in the fall. Other studies have shown that California’s first winter rains might not begin until later in the year, which would worsen fire risk in October and November in the decades ahead.
“There are still a lot of mysteries out there,” Williams said.
