On Wildfires and Climate Change, ‘The Science’ Got in the Way of the Science
Exaggerating the role of global warming in U.S. wildfires only diverts attention from real solutions to both issues.
2020 was a year of crises followed by flawed claims about how to address them. Leading doctors said masks offered no protection from the coronavirus. Politicians called for defunding the police in the midst of rioting and looting.
But among the most head-shaking claims of 2020 was that global warming was the primary cause of the intense summer wildfires that torched some 14 million acres of the American West. Many myths—presented, ironically, as “the science”—spread like wildfire through the media. “Mother Earth is angry,” pontificated Nancy Pelosi. “She’s telling us with hurricanes on the Gulf Coast, fires in the West, whatever it is, that the climate crisis is real and has an impact.” The deputy chief of the California Department of Forest and Fire Protection (CAL Fire), Scott McClean, similarly claimed that “the problem is changing climate leading to more severe and destructive fires.” A few articles dared to suggest that climate change was not the “only” cause of the wildfires. Even fewer hinted at the actual science, which shows that 1) global warming has not been among the primary causes of U.S. wildfires, though it may play a secondary role in some areas, and 2) wildfires in California have dropped by over 80 percent since the arrival of Europeans, and there was less wildfire in California in 2020 than in an average year before 1800.
A splash of sanity came earlier this year from fire science professor Dr. Scott Stephens of the University of California, Berkeley. He said 20 to 25 percent of California’s wildfire damage resulted from climate change, while “75% is the way we manage lands and develop our landscape.” 40-year veteran fire scientist Dr. Jon Keeley of the U.S. Geological Survey put it more bluntly to Michael Shellenberger in Forbes magazine: “It’s almost certainly not climate change. We’ve looked at the history of climate and fire throughout the whole state, and through much of the state, particularly the western half of the state, we don’t see any relationship between past climates and the amount of area burned in any given year.”
It’s a remarkable statement—the opposite of most media narratives. To be clear, the average area burned by California wildfires from 2010-2019 was indeed triple that of 1950-1999. But the flaws in correlating this rise with global warming become especially glaring when comparing annual variations. In the 21st century, year-to-year variations in California’s temperatures have been small, at most about 1-2 degrees Celsius and often closer to zero. However, year-to-year variations in area burned by California wildfires have fluctuated wildly during this same period. For example, the area burned in 2020 was over 16 times that of 2019. It dropped nearly fourfold from 2008 to 2009—and again from 2009 to 2010. Are we to believe that relatively tiny annual temperature variations have been the primary cause of a 16-fold jump and consecutive 4-fold drops in area burned from one year to the next? It’s a bizarre claim, and yet myths repeated by the media, politicians, and even many scientists rest on this false assumption.
“We ought to be much more concerned with ignition sources than a 1- to 2-degree change in temperature,” Dr. Keeley told Scientific American in August. “Show us data that shows that level of temperature increase is actually associated with increased fire activity. They don’t show that.”
In fact, NOAA Climate.gov states that “Since 2000, temperatures have been warmer than average, but they did not increase significantly.” But this did not stop 2020 headlines from suggesting that global warming was causing the world to somehow catch on fire. “Climate change is here, and the world is burning,” wrote the Globe and Mail. “Climate change is a burning global issue,” said a World Wildlife Fund headline.
Media have also rarely mentioned the larger picture at the centennial and millennial scales. In California and Oregon, both the numbers of wildfires and the amount of biomass burned are far lower today than in medieval times or the 1800s, according to the 2012 paper “Long-term Perspective on Wildfires in the Western USA” published in the Proceedings of the National Academy of Sciences by Yale climatologist Dr. Jennifer Marlon and professors from the University of Oregon and ten other major climate research institutions:
Prominent peaks in forest fires occurred during the Medieval Climate Anomaly (ca. 950-1250 CE) and during the 1800s. . . Since the late 1800s, human activities and the ecological effects of recent high fire activity caused a large, abrupt decline in burning similar to the [Little Ice Age] fire decline. Consequently, there is now a forest ‘fire deficit’ in the western United States attributable to the combined effects of human activities, ecological, and climate changes. Large fires in the late 20th and 21st century have begun to address the fire deficit, but it is continuing to grow.
A fire deficit. In fact, this long-term decline in wildfires in the American West is part of a global trend. In a 2016 study, wildfire scientists Stefan Doerr and Cristina Santín wrote:
Many consider wildfire as an accelerating problem, with widely held perceptions both in the media and scientific papers of increasing fire occurrence, severity and resulting losses. However, important exceptions aside, the quantitative evidence available does not support these perceived overall trends. Instead, global area burned appears to have overall declined over past decades, and there is increasing evidence that there is less fire in the global landscape today than centuries ago.
In summary, wildfires in the American West and the world have been declining precipitously for centuries. In fact, the “extreme” area burned in California in 2020 is actually just below that of an average year before 1800, according to data in a 2007 study by Dr. Stephens. Rises in wildfires in recent decades have actually helped toward correcting a fire deficit.
Summer wildfires have been a regular occurrence in the Western U.S. since before humans ever set foot in the region some 15,000 years ago. All regions with Mediterranean climates, including large areas of California, Oregon, and Washington, get plenty of precipitation most of the year but are punctuated by desert-dry summers, which bring annual droughts (and also great beach weather). The rainy seasons build up lush green forests; the summer droughts turn those forests dry and brown. By the end of summer, the slightest spark can ignite a wildfire. This is nothing new. As Dr. Keeley wrote in a 2012 paper, “Summer droughts [in Mediterranean climates] produce an annual fire hazard that contributes to a highly predictable fire regime.”
Since ancient times, societies in Mediterranean climate regions have understood the importance of wildfires and learned to use prescribed fires, also called controlled burns, as a tool. The Greeks and Romans used prescribed fires to clear forests for agriculture. Native Californian tribes such as the Karuk and Yurok used smaller prescribed fires to renew forest food and wood resources and to clear dead trees, branches, and needles from the forest floor to reduce the fuel for—and intensity of—future wildfires.
It was the loss of this ancient understanding of the importance of prescribed fires that, in fact, was among the primary causes of the more intense wildfires we see today. Before Europeans arrived in North America, natural fires would clear out fuel from forests roughly every 10 to 20 years. But a pair of U.S. policies in the 20th century interrupted this natural cycle by aiming to eliminate wildfires altogether. First, the U.S. Forest Service (USFS), established in 1905, banned prescribed burns after the Great Fire of 1910 aka the “Big Blowup”—the largest wildfire in U.S. history—burned three million acres of Montana, Idaho, and Washington in two days. Second, in 1935 the USFS adopted the “10 a.m. policy,” decreeing that every fire should be put out by 10 a.m. the day after it was reported. Under these policies, from 1920 to 1970 the number of wildfires and the area burned in the U.S. plummeted.
But there were unintended consequences. Without periodic fires to keep them in check, California’s forests have grown two to three times denser than pre-1800 levels, according to Dr. Stephens. This density, in turn, has produced an overabundance of flammable fuel on the forest floor. Increased forest density also means too many trees competing for the same nutrients and water, especially in more severe drought years. Trees that could not compete have died straightaway or lost the ability to emit enough of the sap that naturally protects them from bark beetles, which eventually did them in. As a result of this perfect storm of excessive competition, droughts, and bark beetle attacks over the past decade, California today has some 150 million dead trees—some standing, some fallen—which add immensely to the fuel for wildfires.
Specifically, the sharp rise in fallen dead trees in California has been a key factor in extending the duration and intensity of wildfires. Normally, a wildfire burns hottest along its leading edge. Standing dead trees burn and are left behind to smolder, like enormous cigarettes stuck in the earth. But fallen trees lying horizontally across the forest floor become like oversized tinder and go up in flames. In recent decades, this has caused the interiors of wildfires to continue to burn as hot as their leading edges.
With hotter fires running through enormous forests full of dead wood, today wildfires in the American West are spreading much faster than ever before, making them more difficult to track and extinguish. For example, the Creek Fire in Sierra National Forest, California started September 4, 2020 and spread 15 miles in one afternoon, covering over 20,000 acres in four days. It was not declared fully contained until December 24, by which time it had caused the evacuation of over 30,000 people, destroyed over 850 buildings, and cost some $2 million to suppress.
These increases in intensity and speed, however, are only part of the cause of increased wildfire damages in the American West. Just as important is the fact—often overlooked by the media—that the population of California has nearly quadrupled since 1950. And people like to live near the state’s forests—which cover 32 percent of its area; unfortunately, however, that’s where the fires are. In addition, wood—not brick or concrete—is the primary homebuilding material in California due to its abundance of forests, and wood is more flammable than other building materials. So there is simply much more flammable human property around California’s forests than there was before.
In the American West, the primary causes of wildfire ignition are humans and lightning. According to a 2017 study by Dr. Keeley and Dr. Alexandra Syphard of the Conservation Biology Institute, “95% of ignitions are due to humans. As populations increase, we expect a greater chance of ignitions during severe fire weather conditions.” However, wildfires caused by lightning tend to burn much wider areas. According to the Congressional Research Service, “55% of the average acreage burned from 2015 to 2019 was ignited by lightning.” In fact, in 2020 it was an “August lightning siege” of over 12,000 strikes in four days that ignited some 585 wildfires in Northern California, including four of the five largest in the state’s history.
The secondary roles that global warming could play in wildfires include a) increasing rainfall during the wet seasons—in particular during El Niño years—creating more lush forests and thus more fuel, b) altering certain regional wind directions and speeds, which could provide more oxygen to fires, c) lengthening the fire season, and d) increasing the drying effect of droughts on fuel.
But as the consequences of global climate alterations for regional wind and precipitation patterns are so multifactorial, even these secondary roles of global warming are by no means certain—and some could even reduce fires. For example, climatologist Dr. Cliff Mass of the University of Washington blogged at length this past September that he had modeled summer winds blowing over the forested Cascades Range and found that “the number of strong easterly [winds], the kind that start fires, declines under global warming.” Dr. Mass went on to say that—contrary to media reports—global warming did not set the stage for Washington’s 2020 fires by drying out vegetation: “Nearly all of the Washington State fires were grass fires [which] do not correlate well with climate, since grasses and small bushes inevitably dry out sufficiently to burn by early summer. Even if the grass was not initially dry, it would dry out in hours under strong winds.” He added that suggestions that climate change caused these fires are “without any foundation.”
In short, while politicians and media play the climate change card, this narrative only distracts from the true solutions to wildfire damages in the American West, which are known: removing dead trees, both manually and by prescribed burns; reducing human causes of ignition; improving prediction of the paths of spreading fires; and improving response times to suppress fires near human communities. Exaggerating the role of global warming in U.S. wildfires only diverts attention from real solutions to both issues.
Robert C. Thornett is a social science educator and writer who has taught in four colleges and universities as well as international schools in seven countries. His work has been published in Yale Environment 360, Earth Island Journal, The Solutions Journal, and Modern Diplomacy. He currently teaches at the International School of Panama.