How did the fires start?
Officials have not made any statements about the cause of any of the fires yet.
On Thursday morning, Edward Nordskog, a retired fire investigator from the Los Angeles Sheriff’s Department, told me it was unlikely they had even begun looking into the root of the biggest and most destructive of the fires in the Pacific Palisades. “They don't start an investigation until it's safe to go into the area where the fire started, and it just hasn't been safe until probably today,” he said.
It can take years to determine the cause of a fire. Investigators did not pinpoint the cause of the Thomas Fire until March 2019, more than two years after it started.
But Nordskog doesn’t think it will take very long this time. It’s easier to narrow down the possibilities for an urban fire because there are typically both witnesses and surveillance footage, he told me. He said the most common causes of wildfires in Los Angeles are power lines and those started by unhoused people. They can also be caused by sparks from vehicles or equipment.
How do these fires compare to past fires in California?
At about 27,000 acres burned, these fires are unlikely to make the charts for the largest in California history. But because they are burning in urban, densely populated, and expensive areas, they could be some of the most devastating. With an estimated 2,000 structures damaged so far, the Eaton and Palisades fires are likely to make the list for most destructive wildfire events in the state.
And they will certainly be at the top for costliest. The Palisades Fire has already been declared a likely contender for the most expensive wildfire in U.S. history. It has destroyed more than 1,000 structures in some of the most expensive zip codes in the country. Between that and the Eaton Fire, Accuweather estimates the damages could reach $57 billion.
Why are these fires so bad? Is it climate change?
While we don’t know the root causes of the ignitions, several factors came together to create perfect fire conditions in Southern California this week.
First, there’s the Santa Ana winds, an annual phenomenon in Southern California, when very dry, high-pressure air gets trapped in the Great Basin and begins escaping westward through mountain passes to lower-pressure areas along the coast. Most of the time, the wind in Los Angeles blows eastward from the ocean, but during a Santa Ana event, it changes direction, picking up speed as it rushes toward the sea.
Jon Keeley, a research scientist with the US Geological Survey and an adjunct professor at the University of California, Los Angeles told me that Santa Ana winds typically blow at maybe 30 to 40 miles per hour, while the winds this week hit upwards of 60 to 70 miles per hour. “More severe than is normal, but not unique,” he said. “We had similar severe winds in 2017 with the Thomas Fire.”
Second, Southern California is currently in the midst of extreme drought. Winter is typically a rainier season, but Los Angeles has seen less than half an inch of rain since July. That means that all the shrubland vegetation in the area is bone-dry. Again, Keeley said, this was not usual, but not unique. Some years are drier than others.
These fires were also not a question of fuel management, Keeley told me. “The fuels are not really the issue in these big fires. It's the extreme winds,” he said. “You can do prescription burning in chaparral and have essentially no impact on Santa Ana wind-driven fires.” As far as he can tell, based on information from CalFire, the Eaton Fire started on an urban street.
While it’s likely that climate change played a role in amplifying the drought, it’s hard to say how big a factor it was. Patrick Brown, a climate scientist at the Breakthrough Institute and adjunct professor at Johns Hopkins University, published a long post on X outlining the factors contributing to the fires, including a chart of historic rainfall during the winter in Los Angeles that shows oscillations between very wet and very dry years over the past eight decades. But climate change is expected to make dry years drier in Los Angeles. “The LA area is about 3°C warmer than it would be in preindustrial conditions, which (all else being equal) works to dry fuels and makes fires more intense,” Brown wrote.
