‘Santa Ana’ winds and climate change: What is behind wildfires blazing in Southern California?
At least 16 people have been killed in the wildfires that continued to rage in Southern California on Sunday (January 12), powered by Santa Ana winds that gusted to 112 kmph in some places.
The fires have destroyed thousands of acres of land, entire streets, and thousands of buildings in the Los Angeles area, forcing the evacuation of more than 200,000 residents.
How many fires are burning around LA?
This is not the annual fire season in this part of the United States. But as of Friday afternoon (in India), at least five gigantic fires were burning to the north, east, and west of the Los Angeles area.
The Palisades fire, the largest and most destructive, had destroyed more than 20,000 acres in the Pacific Palisades neighbourhood to the west of LA by Sunday. It was only 11% contained as of Sunday afternoon, The New York Times reported.
The next biggest fire, the Eaton fire, is burning to the east of LA. It has so far burned 15,000 acres in the San Gabriel Mountains to the north of Pasadena. It has been contained at around 15%.
The Hurst fire, Lidia fire, and another fire that broke out in LA’s West Hills neighbourhood have burned through between 300 and 1,000 acres so far. As of Sunday, the Lidia fire has been totally contained, the Kenenth fire is at around 90% contained and the Hurst fire is 76% contained.
Role of the Santa Ana winds
These winds blow when high pressure builds over the Great Basin — the area between the Rocky Mountains and Sierra Nevada — and pressure is low over California’s coast. The difference in pressure triggers powerful winds that move from the Basin’s inland deserts east and north of Southern California towards the Pacific Ocean.
As the wind comes down the mountains, it compresses and heats up, and its humidity falls — sometimes to less than 10%. The hot, dry wind dries out forests, and fuels wildfires.
Santa Ana winds are a natural part of California’s climate pattern, and usually blow from October to January. “Winter weather patterns allow high pressure to build near the surface of the Great Basin, which then interacts with low-pressure air over the Pacific,” Rose Schoenfeld, a National Weather Service meteorologist in Oxnard, California, told Bloomberg.
Role of climate change
California experienced its hottest ever June and July, and the second hottest October in 2024. Much of Southern California has had no rain since July, even though half the normal rainy season has already passed. This is the second driest spell in the region in 150 years.
The excessive heat and absence of rain had already turned the vegetation very dry when the Santa Ana began to blow, making the forests even drier and vulnerable to fires.
California’s wildfire season has become longer in recent decades. The state now has twice as many fire weather days (when weather conditions are favourable for wildfires) than in the early 1970s, according to Wildfire Weather: Analyzing the 50-year shift across America, a report published by the nonprofit Climate Central in May 2023.
A 2021 study in the journal Proceedings of the National Academy of Sciences reported that warmer and drier conditions have caused a 66% to 90% of the increase in California’s fire weather days over the last few decades.
The fires have also become more intense. According to a 2023 study published in PNAS, 10 of the biggest California wildfires have occurred in the last 20 years — five of them in 2020 alone.
Another 2023 study published in Nature, which analysed wildfires between 2003 and 2020, noted that the frequency of extreme daily wildfire growth (more than 10,000 acres) has increased by 25% in California compared to pre-industrial times.
All of this is primarily driven by climate change. The rise in global temperatures has led to warmer springs and summers, and earlier spring snow melts. Together, these conditions lead to longer and more intense dry seasons, putting more moisture stress on vegetation and making forests more vulnerable to fires.