A Clear Indication That Climate Change Is Burning Up California
A new study maps the relationship between human-caused warming and Californias summer fires over the past five decades. Updated at 10:50 a.m. ET on June 13, 2023 In the past six years, California has logged three of its five deadliest fires on record, and eight of its 10 biggest. More than 100 people have died, tens of thousands have been displaced, and millions more have been subjected to smoky air, the health consequences of which we dont fully understand . We know that climate change supercharges these fires thanks to the drier environments it creates, but by how much is tricky to say. Fire science is a complicated thing: A blaze might arise from a lightning strike, a hot car on tall summer grass, snapped power lines. But a paper published today in Proceedings of the National Academy of Sciences delivers a fuller sense of the relationship between human-caused warming and Californias wildfires. It finds that climate change is responsible for almost all of the increase in scorched acreage during the states summer fires over the past 50 years. And its authors predict that the increase in burned area will only continue in the decades to come. The arrival of this study is a timely reminder just days after East Coasters endured a toxic haze that originated in Canada: Wildfire is an international problem, and its likely to get worse as time goes on. Using data from 1971 to 2021, the team behind the paper built a model to understand the relationship between wildfire and climate. The researchers then repeatedly simulated worlds with and without climate change. This allowed them to isolate the impact of human-caused climate change versus normal, naturally occurring hot years, and to look at how various factors played a role. They found that human-caused warming was responsible for nearly all of the additional area burned. Read: Wildfire masking is just different A similar approach was taken in a previous modeling paper by one of the authors of this study. It found that factors attributed to human-caused climate change nearly doubled the amount of forest burned in the American West from 1984 to 2015, relative to what otherwise would have been expected. (The increase amounted to an additional 4.2 million hectaresapproximately the combined size of Massachusetts and Connecticut.) Another paper found anthropogenic climate change to be responsible for half of the increase in fire weather in Frances Mediterranean region . This particular paper adds more evidence to the pile. Its whats called a climate-attribution study, a paper that tries to tease out the impact of climate change on shifts in the environment and specific weather events, whether wildfire or hurricanes or sea levels. Experts told me that this style of work can help us better plan for the future by giving us a more precise understanding of different contributing factors. Without careful analyses like this, we would not be able to resolve arguments about the relative roles of climatic and non-climatic factors in driving changes in wildfire, Nathan Gillett, a climate-attribution scientist who works for Environment and Climate Change Canada, told me over email. Troublingly, researchers predict that the number of burned acres from summer fires in California will continue to grow in the coming years, even though so much has already burned. For now, though, much of the state is in a climate lull . Acres burned so far this year are far below average , in part thanks to all the rain this past winter. Canada, on the other hand, is having a downright hellish season. This year is already the countrys third-worst in at least a decade , and its still early. Whats really interesting to me is how extensive the burning is and how early it is this year, Piyush Jain, a research scientist at the Canadian Forest Service and an agricultural, life, and environmental sciences professor at the University of Alberta, told me. Its in May and June, which are not the warmest parts of the summer, even. Jain also noted that several regions are on fire at once, rather than most of the wildfires being focused in the west, as is typically the case. Canada moved to Level 5the most severe ratingon its fire-preparedness scale on May 11. Thats the earliest it has done so in history. Much of whats burning in Canada right now is called boreal forestvery cold northern forests. These forests burn differently than the ones in the American West, though forest management and human activity also play a role. Once the fires have ended, scientists will likely get to work trying to figure out which factors contributed to them. Until studies like the one released today come out, we wont be able to say precisely how much climate change contributed. But whatever the impact on any individual event, climate change is loading the dice for future fire seasons.