Climate consequences: Fire

On January 7, the Palisades and Eaton fires ignited in the hills above Los Angeles and rapidly spread into adjacent neighbourhoods, spawning more fires that ultimately burned more than 16,000 structures and resulted in 29 fatalities.¹

Considerable media coverage was spent on these fires, with predictably wide-ranging views about cause, responsibility, liability, and prevention. One line of commentary linked the fires to climate change, but while some observers drew a clear connection, others skeptically observed that, since fires have been around forever, we had no way to be certain these fires were caused by climate change. 

Climatologists and scientists who study climate change assert it creates more-extreme and more-frequent weather events. Climate change skeptics cast doubt on whether these changes are something to worry about, and insist that in fact warmer weather would be welcome in large areas of the world. Time to dig a bit behind the rhetoric.

Do the frequency and severity of wildfires relate to climate change?

Wildfires are caused by an ignition source, so saying that climate change caused a wildfire is inaccurate. In the last 35 years, most Urban Wildfires were caused by human activity: power line failures, purpose-set fires getting out of control, and arsons. The latest information on the ignition source of the Eaton fire points to an electrical incident on a utility line. Video taken from an Arco station nearby shows flashes on a transmission tower that appear to be arcing, followed minutes later by the outbreak of fire at the base of the transmission tower.² The investigations for sources of the rest of these fires continue. 

Prior to 1990, these types of fires were relatively rare, although they did occur, notably in Australia. Since 1990, there have been more than a dozen of these types of fires, of which the LA fires are the latest. In early August 2023, the most deadly of these fires occurred in Maui, where strong winds and dry conditions drove a wildfire through the town of Lahaina, resulting in widespread evacuations and at least 102 fatalities.³ Urban wildfires have burned the town of Paradise, CA ( Camp fire: 18,000+ structures destroyed, 153,000+ acres burned and 85 people died), Santa Rosa, CA (Tubbs fire: 5600+ structures destroyed, 36,800+ acres burned, 22 people died) and more than a dozen others. 

These fires are becoming more common as a result of several factors. Firstly, they spread rapidly due to very dry conditions. Warmer air is able to hold more moisture in the form of higher humidity. On average a 1º C increase in atmospheric temperate enables it to hold 7% more moisture.^4,5 This moisture comes from various sources but the one affecting the spread of these fires is the drying of vegetation. Trees, underbrush and plants are dryer than they usually are in many of the locations where these fires occur, partially because their moisture is drawn into the warmer surrounding air. In addition, drought conditions have become more pervasive in Southern California, with the Los Angeles area only receiving .29” of rain since May 1, 2024.⁶

Wildfires release vast quantities of CO2 in a relatively short period of time. Urban wildfires release more CO2 per acre than a forest/grassland fire due to the nature of the material burned. The Palisades and Eaton fires released about 1.5 million tons of CO2, which is roughly equivalent to annual emissions from 325,000 automobiles or electricity use for 220,000 homes. This of course creates a self-reinforcing system: CO2 from wildfires increase global warming, resulting in more wildfires.

We are all familiar with the orange haze of wildfire smoke, with its acrid smell and ability to sting our eyes. Urban wildfires are even more noxious and unhealthy than rural wildfires, because you are breathing in televisions, cars, and roof shingles. In the case of the LA Urban Wildfires the atmospheric content of lead, chlorine, and other chemicals exceeded EPA safety standards. ⁷

In 2016, an Urban Wildfire burned into the town of Fort McMurray, Alberta, causing the evacuation of 88,000 people, destroyed more than 2400 structures and became Canada’s costliest natural disaster with $9.9 billion in damages. John Vaillant wrote a book called Fire Weather: The Making of a Beast which explores the fire in detail, including its link to climate change.⁸ Valliant made the case that this was a new type of fire that was introducing itself to the world. He argued that we needed to come up with better way to prevent them, and design our urban environment to better deal with them. With 10 fires since 2016 – many as bad or worse – we are clearly not heeding the warning or responding. 

Enough said.

Reading

1. “California Department of Forestry and Fire Protection | CAL FIRE.” Accessed February 12, 2025. https://www.fire.ca.gov/.

2. Penn, Ivan, Blacki Migliozzi, Danny Hakim, and K. K. Rebecca Lai. “Flashes Then Flames: New Video of Eaton Fire Raises More Questions for Power Company.” The New York Times, January 26, 2025, sec. U.S. https://www.nytimes.com/2025/01/26/us/los-angeles-eaton-fire-cause.html.

3. US EPA, REG 09. “Maui Wildfires.” Overviews and Factsheets, August 29, 2023. Southwest, Hawaii. https://www.epa.gov/maui-wildfires.

4. “Water Vapor.” Text.Article. NASA Earth Observatory, November 30, 2024. https://earthobservatory.nasa.gov/global-maps/MYDAL2_M_SKY_WV.

5. DAVID M. ROMPS, "Clausius–Clapeyron Scaling of CAPE from Analytical Solutions to RCE."Department of Earth and Planetary Science, University of California, Berkeley, and Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, June 5, 2016.

6. Graff, Amy. “A Dangerously Dry Southern California Was Ready to Burn.” The New York Times, January 8, 2025, sec. Weather. https://www.nytimes.com/2025/01/08/weather/southern-california-fire-winds-dry.html.

7. Graff, Amy. “A Dangerously Dry Southern California Was Ready to Burn.” The New York Times, January 8, 2025, sec. Weather. https://www.nytimes.com/2025/01/08/weather/southern-california-fire-winds-dry.html.

8. Vaillant, John. Fire Weather: The Making of a Beast. New York: Alfred A. Knopf, 2023.