Where there’s smoke, there’s fire: a look at the climate change fingerprint on the California fires

This fall, Congresswoman Alexandria Ocasio Cortez retweeted a picture of the Vallejo Fire in Northern California, captioning it, “This is what climate change looks like.” She is far from the only one making this point. A few hours later that day, the Los Angeles Times ran an editorial: Climate change has set California on fire. Are you paying attention? 

Crews fight the 2017 Thomas Fire in Ventura County, California. The Thomas Fire took six months to extinguish, burned almost 300,000 acres, and was the largest fire recorded in California until the Mendocino Complex Fire in 2018. (Photo Credit: Forest Service Photo by Kari Greere)


At the time of writing, California was in the midst of another devastating fire season; there were ten active fires burning across the state. The weekend that the Kincade Fire ignited and swept through Sonoma County, I read nervously as the fire’s footprint climbed into the tens of thousands of acres and forced evacuations of hundreds of thousands of people. As a former resident of northern California, I know the places going up in flames, though I have never experienced and cannot imagine the trauma of evacuating one of these events. If you have lived in California during the past decade, you have probably had at least an indirect experience with fire – smoky air blanketing your city, fire burning along a highway, evacuated friends crashing on your couch. 

Fire conditions are worsening – the LA Times reports the last two years have seen five of California’s 20 deadliest fires, and 10 of the 20 most destructive fires have burned during the last 10 years. Residents name off these events like hurricanes: this year’s Kincade Fire that forced evacuation of 200,000, the fires last year that set and reset destructive records. Outraged politicians and residents in northern California seem to be pointing two fingers, one at the utility company, Pacific Gas and Electric (PG&E) – and one at global climate change.

The Kincade fire, north of Santa Rosa, was visible from space in October 2019, covering more than 76,000 acres. The fire ultimately destroyed over 370 structures before it was contained. (Photo Credit: NASA Earth Observatory image by Lauren Dauphin, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview, and the Suomi National Polar-orbiting Partnership)


While we cannot attribute any individual extreme event to anthropogenic climate change, each passing year makes the pattern clearer – the likelihood of destructive fire and other extreme events becomes far greater under climate change scenarios than under past conditions.

To start a campfire, one needs dry wood and paper, air flow, and a lighter. Starting a wildfire is no different; in the most basic sense, all it takes is abundant dry vegetation, wind, and a spark. The first piece of the equation is where we see the clearest evidence for climate change as a cause of wildfire in California. In a 2016 study, researchers found that while a number of factors have contributed to forest fire activity in the western United States, warming and drying have made fuels drier during fire season. 

California has warmed more than 3 degrees Fahrenheit on average over the past century, and hotter temperatures and drier air dry out vegetation throughout the spring and summer. By late summer and fall, forests and shrublands are more susceptible to ignition. Researchers demonstrate that anthropogenic climate change caused more than half of documented increases in fuel dryness and doubled forest fire area since the 1980s – providing the clearest link between climate change and wildfire in California. A study published this summer found that California has experienced an eightfold increase in summer forest-fire extent since the 1970s. Rising summer temperatures have significantly increased the vapor pressure deficit, resulting in drier summer fuels. Fall forest fires also have access to more dry fuel, increasing the potential for large fires. 

Climate change is strongly linked to hotter summers resulting in drier vegetation in many parts of California. Dry forest and grassland fuels can easily ignite by late summer and fall. (Photo Credit: Charlotte Dohrn)


Wind, in addition to dry fuel, increases fire risk in California. “Red flag” warnings are declared when forecasts for strong winds, low humidity, and other risk factors align. Seasonal high wind events are common. The Kincade fire that scorched wine country and neighboring communities this fall was fanned by the Diablo winds – gusts reached 96 miles per hour. The Santa Ana winds in southern California are similarly strong. Increases in extreme weather events are a commonly cited impact of climate change. However, climate models predict reduced frequency and intensity of the Santa Ana winds, and the record shows no change in offshore wind events since the 1900s. 

Climate change, natural weather events and variability, failed housing policy that has pushed development in fire-prone areas, and a legacy of fire suppression all combine to create a tinderbox ready for a match. And in the case of many of Northern California’s recent fires, the match has been PG&E equipment failure. The bankrupt utility has come under intense criticism for failing to maintain its infrastructure and modernize its grid, while prioritizing profit and paying out dividends to shareholders. 

A fire breaks out near Yosemite National Park in late summer, 2015. Fires that start in remote wilderness areas can spread to communities in the wildland-urban interface when propelled by strong winds. (Photo Credit: Charlotte Dohrn)


Some of the PG&E towers on the line that sparked the deadly fire in Paradise, California were 100 years old – eligible to be listed on the national register of historic places. This year, the utility started implementing public safety power shut offs – at one point shutting off power to more than two million people – to reduce fire risk. This practice, which has sparked public outcry, may be a grim example of the realities of climate adaptation. California’s Governor Gavin Newsome summed up a perspective held by many, “It’s about dog-eat-dog capitalism meeting climate change. It’s about corporate greed meeting climate change. It’s about decades of mismanagement.” The risk in blaming climate change is that governments and other actors will ignore the underlying structural problems – the public and policymakers in California seem to be trying to avoid this pitfall by demanding changes to the electricity grid. 

In California and elsewhere, the intersection of climate change and corporate greed is deadly and vulnerable populations often bear the greatest burden. Though fires have burned through wealthy and low-income areas alike, astonishing stories of inequity emerge from the firescape: the poor and disabled take on stress and debt during power outages, inmates fight fires for minimal compensation, the homeless have limited options to access fresh air, agricultural workers continue to harvest as fires approach, and undocumented residents cannot access federal relief funds. Area burned in the United States is one among many distressing climate-linked trends. Without immediate climate action, the science suggests that fire in California, and other impacts of the climate crisis, will only become more acute. 

The hills to the south of Ocean Beach, San Francisco were obscured by smoke during the devastating fire season in 2018. Health impacts of fires are of increasing concern in urban areas and often disproportionately felt by vulnerable populations. (Photo Credit: Daniel Kadvany)