Climate Change Fuels Wildfire Increase: Livermore Researchers

LIVERMORE, CA — Human-caused climate change could be playing a significant role in fueling the surge of devastating wildfires in California, a Lawrence Livermore National Laboratory scientist and his collaborators say in a new report.

The research, published in "Proceedings of the National Academy of Sciences," determined that nearly all recent increases in wildfire burned areas is attributed to climate change caused or influenced by humans, either directly or indirectly, rather than to natural climate variation.

Funded by a UC-National Lab Collaborative Research and Training Award on Mitigating and Managing Extreme Wildfire Risk in California, the report shows that "nearly all the recent increase in summer wildfire burned area is attributable to human-caused (anthropogenic) climate change," a news release on the report said.

California's summer wildfire seasons have only increased in intensity in recent years and the study shows the average summer burn area in forests in northern and central portions of the state have increased fivefold between 1996 and 2021 compared to between 1971 and 1995.

"Over the past 50 years, the area burned by summer wildfires in California has been increasing," the news release said. "The 10 largest California wildfires all happened in the last 20 years, five of which occurred in 2020 and eight after 2017."

In their research, the team found that since at least 2001, most drivers of the severity and extent of wildfires is anthropogenic.

"We show that nearly all of the observed increase in burned area in California over the past half-century is attributable to human-caused climate change," LLNL scientist Don Lucas, co-author of the study, said.

As human-caused climate change continues, the average burn area for wildfires could increase up to 52 percent between 2031 and 2050, the study said, adding that along with higher burn area averages comes potentially higher rates of harm on human health and the surrounding environment.

The team, led by Marco Turco from the University of Murcia, Spain, modeled the climate drivers of summer wildfire activity in California, both with natural climate variation alone and with anthropogenic climate change effects, the news release said. The simulations with anthropogenic climate change effects yielded burn areas an average of 172 percent higher than natural variation simulations.

"The results show the role of human-caused climate change in driving fire activity and highlight the need for protective adaptations against summer wildfire seasons," Lucas said.

Researchers also noted other, non-climatic factors that can influence a wildfire's characteristics, like land management, more development in fire-prone areas and the vulnerability of the state's power grid amid extreme weather. "Beneath these 'external' factors, natural climate variability also influences the occurrence and severity of forest wildfires, creating a noise that can mask the signal of human-caused impacts on wildfire changes," Lucas said.

According to the report, non-climatic factors that have been implicated in changing wildfire characteristics include land management that has facilitated fuel buildup, causing increased burn severity, and the increased susceptibility of California’s aging power grid to extreme weather and increased development in fire-prone areas that changes ignition patterns and fire management.

“Beneath these ‘external’ factors, natural climate variability also influences the occurrence and severity of forest wildfires, creating a noise that can mask the signal of human-caused impacts on wildfire changes,” Lucas said.

Using the latest simulations for climate-change attribution and detection studies and accounting for the uncertainties arising from the data-driven climate-fire model and climate models, the team quantified the influence of human-caused climate change on the burned area in recent years.

We show that nearly all of the observed increase in burned area in California over the past half-century is attributable to human-caused climate change,” Lucas said.

Other institutions involved in the study include the University of Murcia, Spain; University of California, Merced; University of Cantabria, Spain; University of California, Los Angeles; University of California, Irvine; and the Barcelona Institute for Global Health.

To see the study in full, click here.