Wildfires in California destroyed five times more areas between 1996 and 2020 than they did from 1971 to 1995. Investigators from the University of California and other international institutions have established that human-caused climate change is to blame for nearly all of the increase in scorched terrain.
In October 2020, the Silverado fire illuminated the night sky above Orange County. In a new paper in Proceedings of the National Academy of Sciences, researchers—including Amir AghaKouchak of UCI’s Department of Civil and Environmental Engineering —say that nearly all of the increase in burned area from California’s wildfires in the past three decades is attributable to anthropogenic climate change. Image Credit: Amir AghaKouchak/UCI
The research team used climate modeling to discover that “anthropogenic forcing”—conditions caused by human fossil fuel burning and land use practices—accounted for a 172% increase in burned area over natural inputs alone. The study was published in the Proceedings of the National Academy of Sciences.
The 10 largest fires in California history have all occurred in the past two decades, and five of those have happened since 2020. Through our study, it has become clear that anthropogenic climate change is the major driver of this increase in wildfire damage.
Amir AghaKouchak, Study Co-Author and Professor, Civil and Environmental Engineering, University of California, Irvine
Below-average precipitation, increased temperature in the spring months, reduced springtime mountain snowpack, hotter summer temperatures, more frequent heat extremes, and a decline in rainy days during the fire season are among the major factors linking wildfire risk to climate change highlighted in the paper.
Climate change and variability, according to scientists, are also to blame for a higher vapor pressure deficit, which is the difference between the amount of moisture in the atmosphere and how much moisture the air can store when saturated. This adds to arid conditions as well as dried-out fuels on the forest floor and canopy, which cause wildfires.
According to AghaKouchak, in addition to causing havoc on the environment, wildfires wreak havoc on individuals, aggravating mortality and poor health outcomes, with people of lower socioeconomic status bearing the brunt of the consequences.
The researchers used the Detection and Attribution Model Intercomparison Project, part of the extensively used Coupled Model Intercomparison Project Phase 6. The models were used to study the potential spread of the Golden State’s burned area through 2050, in addition to evaluating the effects of human climate change on forest fires in California since 1971.
We found that we can expect as much as a 50 percent increase in burned area from 2031 to 2050 relative to the past few decades.
Amir AghaKouchak, Study Co-Author and Professor, Civil and Environmental Engineering, University of California, Irvine
While the study offers a dark picture of human influence on the Earth system, he believes that the presence of anthropogenic climate change-driven fires can be the reason for hope.
Our paper makes it clear that the problem is ours to fix and that we can take steps to help solve it. By acting now to reduce our carbon dioxide emissions and pursue more sustainable transportation, energy production, and agricultural practices, we can reduce the adverse effects of global climate change.
Amir AghaKouchak, Study Co-Author and Professor, Civil and Environmental Engineering, University of California, Irvine
Investigators from Spain’s University of Cantabria and Barcelona Institute for Global Health; UC Merced; UCLA; and Lawrence Livermore National Laboratory collaborated with AghaKouchak and main author Marco Turco, a postdoctoral researcher at the University of Murcia in Spain.