The New Year has rung in with one of the most horrific wildfire events in world history: an urban firestorm in the Los Angeles metro area that has killed at least five people and reduced thousands of homes to smoking rubble. Two major fires in excess of 10,000 acres – the Palisades fire in the western suburbs of Los Angeles, and the Eaton fire in the northern suburbs – were intensified by severe drought and driven by winds gusting up to 100 mph (161 km/hr) from a severe Santa Ana wind event.
Climate scientist Daniel Swain said on CNN that the Pacific Palisades fire alone may end up as the most expensive wildfire in history, and that he expected that collectively, the fires ravaging the region will be the costliest wildfire event in history. According to NOAA, the most expensive wildfire season on record (in 2024 USD, to account for inflation) was the $30 billion 2018 season, mostly because of severe fires in California. This included the most destructive wildfire on record – the November Camp Fire, which devastated Paradise, California, killing 85 and destroying over 18,800 buildings. That fire cost about $12.5 billion, making it the most expensive single fire in world history.
“Since Oct. 1, the beginning of the water year, downtown Los Angeles has received 0.16 inches of rain — a tiny fraction of the average 4.64 inches that the area gets by this point in the season.” https://t.co/ZEp6Rq2d49
— Paul Beckwith (@PaulHBeckwith) January 9, 2025
The role of climate change in the fires
The main way that climate change worsens wildfires is by drying out vegetation. Prolonged heat turns forests and grasslands into tinder, fueling faster, more intense burns. In the case of this week’s fires, vegetation growth in early 2024 was enhanced by a wetter-than-average winter in Southern California. But during the summer of 2024, California experienced its hottest summer on record. This record heat, combined with near-record dryness, dried out the plentiful vegetation that grew in response to the wet winter. Moreover, Southern California’s wet season, which usually begins in October or November, was delayed, and by January 2025, severe drought conditions were in place (Fig. 1).
In an email, climate scientist Daniel Swain offered these insights on the California climate change/wildfire connection:
California’s fire season has already lengthened considerably in a warming climate. Critically, this has increased the overlap between “critically dry vegetation season” and “offshore wind season” (Oct-Jan). There is little evidence for climate change affecting Santa Ana winds themselves, but there is strong evidence that climate change has greatly increased the occurrence of extreme fire weather conditions in Southern California in autumn and early winter (Goss et al. 2020, Climate change is increasing the likelihood of extreme autumn wildfire conditions across California). Climate change has also increased the seasonal overlap of dry/windy conditions (Swain 2019), and there is evidence that further warming will increase wet-to-dry “hydroclimate whiplash” transitions (which result in abundant vegetation growth then subsequent drying; see my new paper, Hydroclimate volatility on a warming Earth). Additionally, the California “shoulder season” precipitation (autumn and spring) will likely decrease with warming, adding to the effects of warming temperatures and increasing evaporative demand (drying out of vegetation) essentially year-round.
There are two other important ways that a longer dry season from climate change worsens wildfires:
- Scarcer water supplies because of more intense droughts hinder firefighting efforts and recovery.
- There are fewer safe days for prescribed burns, making it harder to reduce fuel loads in vulnerable areas before fire season starts.
A 2023 study found from 1971 to 2021, human-caused climate change contributed to a +172% increase in burned areas in California, with a +320% increase from 1996 to 2021. In the coming decades, a further increase in annual forest burned areas is expected, ranging from 3% to 52%.
Wildfires are growing much faster than they have before in California and other Western states. “From 2001 to 2020, the average peak daily growth rate for these fires more than doubled (+249% relative to 2001) in the Western US.” https://t.co/n8SrCEHv8R
— Zeke Hausfather (@hausfath) January 8, 2025
Comparing the 2025 and 2011 severe Santa Ana wind events
This week’s fires were driven by the intense winds of a severe Santa Ana wind event. On Wednesday, Jan. 8, at least 32 stations in the Los Angeles area recorded wind gusts of at least 70 mph, with the highest being a 100-mph (161 km/hr) wind gust at Mt. Lukens Truck Trail, located about 20 miles (32 km) north of Los Angeles. The last Santa Ana wind event of similar intensity occurred over 13 years ago, on Nov. 30-Dec. 1, 2011. During that event, widespread wind gusts over 70 mph (113 km/hr) toppled thousands of trees, and over 200,000 homes lost electricity, mostly in the northern Los Angeles suburbs of Altadena and Pasadena. Whitaker Peak (elev. 4,120 feet), located about 50 miles (80 km) northwest of Los Angeles, recorded a gust of 97 mph (156 km/h).
Fortunately, no major wildfires were sparked the 2011 Santa Ana wind event. This was largely because Los Angeles was not experiencing drought at that time. But in the case of the 2025 event, severe drought was in place (Fig. 1).
California: Here is a great look at the winds pilots and firefighters are dealing with over these California fires. #cafire #palisadesfire #eatonfire
It’s very difficult to get the retardant to go where you want it to with the ridge top winds blowing both the product and the… pic.twitter.com/ijzJvPZp9W
— The Hotshot Wake Up (@HotshotWake) January 9, 2025
Spells of dangerous fire weather will continue into next week
There’s no immediate end in sight for the bone-dry conditions and periods of strong Santa Ana winds plaguing coastal Southern California. The most intense winds from Wednesday have slackened, but the overall pattern — a strong upper-level high over the eastern Pacific, and energy diving southward through California, pushing winds downslope and offshore — will stay in place well into next week. Not only will this keep the door closed for any major precipitation, but it will make it tougher to fight the ongoing fires and to address any new ones.
Critical fire-weather conditions are predicted to remain in place over coastal Southern California through early Friday, according to the NWS Storm Prediction Center. Winds could gust to 20-30 mph in the valleys and 40-60 mph at higher elevations, especially on Thursday night. After a brief break, another pulse of strong north to northeast winds is expected this weekend, and a more serious Santa Ana wind setup could develop on Monday and Tuesday. Forecasters at the National Weather Service office for the Los Angeles area were already noting next week’s setup in a forecast discussion on Thursday:
“This would be concerning with likely no rain expected and the Tuesday night-Wednesday time period being the fourth offshore event in the stretch. There is great concern that fire weather conditions could become exacerbated given the antecedent conditions, little rain across the area since the Spring of 2024, and another offshore wind event on top of all of what we have seen, so far. Residents are urged to stay tuned to latest information and remain vigilant in steps to protect your life and property.”
