On January 7, 2025, several fires broke out in the city of Los Angeles and its surrounding areas. The flames ravaged entire communities and tens of thousands of people were evacuated. The provisional death toll stands at ten deaths on the morning of Friday January 10, while the fires are still not under control.
When residents of the Pacific Palisades neighborhood west of the City of Angels saw flames rising from the hills on Tuesday morning, the fire had grown to only 10 acres. Twenty-five minutes later, he had reached 80. According to the BBCat least five factors explain the speed and intensity with which the flames engulfed an entire part of Los Angeles.
The accumulation of plant fuels
In 2024, the El Niño weather phenomenon led to significant precipitation and, with it, a high risk of fires for the winter of 2025.
“We often think that rain is bad for fires, says Rory Hadden, a fire science researcher at the University of Edinburgh. But this is only true if it appears at the time of the fire. On the other hand, precipitation that precedes a fire can encourage the growth of vegetation, which then becomes a potential fuel. “We then enter a period of drier weather, continues the researcher. So the vegetation dries out very, very quickly, and it is more abundant. We can therefore accumulate more fuel.”
Fire destroys buildings and vegetation as flames rage in Los Angeles, California, January 9, 2025. | Official Flickr Account of CAL FIRE / Handout / Anadolu / AFP
This phenomenon of transition from very humid weather to very dry weather is known as «hydroclimate whiplash» (literally “hydroclimatic whiplash” in French). A recent study suggests that the risk of this phenomenon occurring has increased from 31 to 66% on a global scale since the mid-20th century.e century.
The Santa Ana “hairdryer” effect
Another factor responsible for the speed with which the fires spread was the windstorm that transformed the flames born west of Los Angeles into a full-blown wildfire. These winds are often hot and dry and can then help drive moisture away from vegetation. This specific breath of California is known as Santa Ana.
This satellite image shows an overview of the fire in Pacific Palisades, a neighborhood in Los Angeles, California, on January 9, 2025. | Planet Labs PBC / AFP / XGTY
“These winds are very, very dryexplique Rory Hadden. They move very, very fast, so as soon as a fire starts, it’s very easy for it to spread and grow very, very quickly. We saw winds reported at over 100 miles per hour. So, of course, that just fuels the flames and spreads those fires.”
The embers
Strong winds not only fan the flames and spread them, they also carry embers. These, according to Rory Hadden, “are the leading cause of structural loss in fire”. The researcher explains that the flames are slowed down by buildings or roads. On the other hand, nothing can stop the embers.
Wind pushes embers into a home as the Eaton Fire moves through the area January 8, 2025 in Altadena, California. | Justin Sullivan / Getty Images North America / AFP
Thanks to the winds, they can jump several kilometers and cause new fires. They are thus responsible for a sort of domino effect, and are also very dangerous for humans.
Hills and canyons
It appears that the terrain in the Los Angeles region also increases the risk of fire. According to Rory Hadden, canyons and ravines give rise to very extreme fire behavior that is difficult, if not impossible, to control.
In this aerial view, destroyed homes can be seen as the Pacific Palisades Fire continues to burn, January 9, 2025 in Malibu, California. | Mario Tama / Getty Images North America / AFP
In addition, this type of topography makes evacuations all the more complicated. Mike Bonin, former Los Angeles city councilman, explains to the New York Times that in the Pacific Palisades neighborhood, narrow hillside roads present an additional challenge for people trying to leave.
Climate change
Climate change is contributing to the increase in the scale of fires around the world.
Burnt trees and smoke from the Pacific Palisades Fire seen from Will Rogers State Historic Park with downtown Los Angeles in the distance, January 9, 2025. | Apu Gomes / Getty Images North America / AFP
“The weather is warmer, but it also comes with more extreme winds and more intense rains that allow vegetation to grow, concludes Rory Hadden. So we’re facing this sea change, not just with hotter and drier weather, but also wetter and windier, and all that climate-wise that entails. This is what will define risk in the future.»
Source: www.slate.fr
