California Wildfire Analysis from Scripps Oceanography Climate Experts
Scripps Oceanography experts answer questions on the Los Angeles wildfires
Credit: ALERTCalifornia/UC San Diego
What is causing these high winds?
Sasha Gershunov (Climate Science Researcher): High pressure in the Great Basin and low pressure over northern Baja California, plus a very strong jet stream roaring southwestward over SoCal is enhancing the surface Santa Ana winds.
What is making these winds so unprecedented?
Sasha Gershunov: This is an unusual Santa Ana given the amplified jet stream pattern (upper air support) but the timing is not unusual. December and January are the peak of the Santa Ana wind season.
The LA fires are burning in the swath of the extreme rainfall from atmospheric rivers (ARs) that fell there last January, which means there is an abundance of grasses and other fuels. And if high-intensity precipitation makes landfall, it will likely produce debris flows when they bring torrential rains to burn scarred landscapes.
Are these conditions abnormal for this time of year? Is climate change contributing to these winds?
Sasha Gershunov: Santa Anas are typical for this time of year. What is unusual is the fact that we haven’t had any significant rain by now. This is reminiscent of 2017-18 when the Thomas Fire burned through most of December and into January. It ended with an AR and a deadly debris flow from the fire scar above Montecito.
We’ve seen a trend towards more frequent weather patterns driving Santa Ana wins (SAWs) — https://link.springer.com/article/10.1007/s00382-022-06361-7 — though this trend is not projected for the future.
How well are these conditions conforming to forecasts of the changing timing of Santa Ana wind events made in the last 10 years?
Sasha Gershunov: Models project somewhat fewer SAW events in the fall and spring but warmer and drier SAWs. Santa Ana wind intensity is not projected to diminish. Their activity will always peak in December-January. Timing is not unusual. This is an unusual event, meteorologically, though.
What is the cause of these wildfires?
Daniel Cayan (Climate Science Researcher): To large degree the recent fires result from an unfortunately very late arrival (it hasn't arrived yet) of North Pacific storminess — persistent high pressure weather has made Southern California extraordinarily dry. The added ingredient is Santa Ana winds, which aren't unusual but when they occur during these late arrival autumns and early winters, they are extremely hazardous because the landscape is so desiccated. An added effect may be that there has been a tendency over the last five decades for the high pressure weather systems in autumn and early winter to occur more frequently — maybe a symptom of climate change but still uncertain on that point.
Sasha Gershunov: Early and mid-winter fires can grow very large as they can be spread by consecutive Santa Ana winds common in this season.
Los Angeles has only received 0.16 inches of rain since October, more than 4 inches below average. How anomalous is this dry spell in Southern California?
Julie Kalansky (Climate Scientist and Deputy Director for Operations at the Center for Western Weather and Water Extremes): While this is not unprecedented, as there have been other years with extremely low precipitation, up until this point in the water year it is anomalous. This map shows the different percentiles for stations that have long term reliable precipitation records. Further, this graphic aggregates the greater Los Angeles area precipitation that shows how anomalous this year has been. Based on this approach, 1963 was even lower, but not by much.
Sasha Gershunov: 1962-63 and 2017-18 are so far nearly tied with this year in terms of the late start to winter rains in SoCal. Tomorrow this year will surpass 2017-18 when the smoldering remains of the Thomas Fire were put out by an AR that caused a deadly debris flow in Montecito, Santa Barbara County.
Is any precipitation for Southern California possible in the upcoming forecast?
Julie Kalansky: The recent Center for Western Weather and Water Extremes subseasonal outlook (week 3) suggests the potential for a regime change towards the end of the month. Given the long lead time, there is uncertainty associated with this forecast, but hopefully there is indication there is some relief to the dryness.
How dangerous is wildfire smoke to public health?
Tarik Benmarhnia (Climate Change Epidemiologist): Wildfire smoke is a mixture of pollutants (gas and aerosols) and the most studied component is fine particles (PM2.5: particles smaller than 2.5um that can get into the lungs until the alveola and penetrate the bloodstream). There are several harmful health effects associated with both short-term exposure and long-term exposure to PM2.5. Short-term effects are mostly about exacerbation of existing medical conditions such as asthma exacerbations among people already living with asthma. Long-term effects relate to how individuals or communities repeatedly exposed to PM2.5 can develop some diseases such as lung cancer, cardiovascular diseases or dementia. PM2.5 are emitted from various sources but in California and the Western U.S. more generally, wildfire smoke is becoming the main source of air pollution and PM2.5 in particular. The regulation on air pollution (National Ambient Air Quality Standards (NAAQS) does not distinguish PM2.5 according to the source of pollution. Yet, recent evidence from our study shows that wildfire smoke is several times more harmful to respiratory health than similar levels of pollution from other sources.
The vast majority of the epidemiological evidence related to wildfire smoke is focusing on short-term effects. As wildfires are becoming more frequent, some communities are repeatedly exposed to wildfire smoke and studying long-term effects becomes critical. We recently showed that people being repeatedly exposed to wildfire smoke PM2.5 over multiple years are more likely to develop dementia and Alzheimer's diseases. (https://pubmed.ncbi.nlm.nih.gov/39585704/)
How can people protect themselves from wildfire smoke?
Tarik Benmarhnia: At the individual level: wear ffp2 mask, use indoor air filters — high efficiency particulate air filters — and reduce outdoor activities and avoid any physical activity. For some individuals with pre-existing conditions some medications can help reduce the negative symptoms and exacerbations. For more information see: https://www.nejm.org/doi/full/10.1056/NEJMsr2028985.
How is UC San Diego’s ALERTCalifornia monitoring these fires? How many cameras are in California?
UC San Diego’s ALERTCalifornia public safety program currently manages more than 1,140 cameras across the state. Emergency managers as well as the public are utilizing these cameras day and night to monitor situations on major fires in Los Angeles and around Southern California.
ALERTCalifornia’s high-definition cameras are able to pan, tilt, zoom and perform 360-degree sweeps approximately every two minutes. The cameras also provide 24-hour monitoring with near-infrared night vision capabilities. Each can view as far as 60 miles on a clear day, and 120 miles on a clear night. Using the cameras and associated tools, first responders with the California Department of Forestry and Fire Protection (CAL FIRE), and other federal, state, and local government agencies can rapidly confirm fire ignition, quickly scale fire resources, support evacuations through enhanced situational awareness and monitor fires through containment.
ALERTCalifornia Cameras in Southern California by county:
- Kern County: 63 cameras at 32 individual sites.
- Los Angeles County: 115 cameras at 52 individual sites.
- Orange County: 54 cameras at 17 individual sites.
- Riverside County: 55 cameras at 22 individual sites.
- San Bernardino County: 47 cameras at 26 individual sites.
- Ventura County : 40 cameras at 20 individual sites.
- San Diego County: 148 cameras at 34 individual sites.
How can media access these cameras?
ALERTCalifornia’s cameras can be viewed live 24/7 at cameras.alertcalifornia.org.
Clips and screen captures are available for media use with required on-screen credit given to “ALERTCalifornia | UC San Diego.” Please email Caitlin Scully for access to media clips.
What could the financial impact be of these fires?
Tom Corringham (Climate Change Economist): Wildfires have become billion-dollar disasters with alarming frequency. Since 2018, California's annual wildfire costs have skyrocketed, up to ten times higher than the previous 50-year average. The 2018 Camp Fire caused over $16 billion in damages, with lives lost and entire communities displaced. The Dixie Fire in 2021 cost over $600 million in suppression costs alone.
Wildfires tear through every part of the economy — homes are lost, businesses close, crops are wiped out, and tourism dries up during the fire season. The ripple effects can last for years. The true cost isn't just in property. Health impacts, from smoke inhalation to mental health struggles, often rival the price of fighting the fires themselves.
Long after the flames are gone, wildfires leave scars on local economies — tax revenue drops, rebuilding takes time, and people leave towns that may never fully recover. A severe fire can erase decades of economic growth in a matter of hours.
How will economists assess the impacts after these fires after the fact?
Tom Corringham: Wildfire costs include the visible damage and the hidden ripple effects. Direct costs like property damage and firefighting show up fast and can be tracked through insurance claims, government reports, and agency budgets. Business losses and supply chain disruptions don’t always make headlines, but show up in tax records to industry surveys. Health costs can be quantified using hospital admissions, insurance payouts, and public health data.
Economists measure the true cost of wildfires by connecting all the dots, from burnt homes, lost jobs, and economic slowdowns, to health impacts and the long-term environmental costs of ecological devastation.
More information on how climate change is impacting California can be found here: https://scripps.ucsd.edu/research/climate-change-resources/faq-climate-change-california.
Related studies on Santa Ana winds:
Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in southern California - October 2022
More Evidence that California Weather is Trending Towards Extremes - August 2022
Climate Change May Suppress Santa Ana Winds, Particularly in Fall - January 2019
Related studies on wildfire smoke hazards:
Unhoused People are Highly Vulnerable to Wildfire Smoke - November 2024
Quoted Scientists
About Scripps Oceanography
Scripps Institution of Oceanography at the University of California San Diego is one of the world’s most important centers for global earth science research and education. In its second century of discovery, Scripps scientists work to understand and protect the planet, and investigate our oceans, Earth, and atmosphere to find solutions to our greatest environmental challenges. Scripps offers unparalleled education and training for the next generation of scientific and environmental leaders through its undergraduate, master’s and doctoral programs. The institution also operates a fleet of four oceanographic research vessels, and is home to Birch Aquarium at Scripps, the public exploration center that welcomes 500,000 visitors each year.
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