Washington — A scientific study found that human-caused climate change made the hot, dry, and windy conditions worse, which helped fuel the recent severe wildfires in Southern California.
The many reasons for the ongoing fires are complicated. Therefore, the impact of global warming on the recent weeks of burning seems limited when compared to earlier studies of extreme heat, floods, and droughts by the World Weather Attribution team. Tuesday’s report, too rapid for peer review yet, found global warming boosted the chance of high fire weather conditions in this month’s fires by 35% and its intensity by 6%.
Strong Santa Ana winds that happen once every ten years, a dry autumn after two very wet years, hot weather, dry air, and houses in areas prone to fires all contributed to fast-moving fires. These fires destroyed thousands of homes and resulted in at least 29 deaths, according to the study’s authors. The climate attribution team could only measure factors related to the fire weather index, which includes the weather conditions that increase the risk of fire.
The fire weather index looks at past rainfall, temperature, and wind speed. The team studied this index to find signs of climate change that they could measure.
The team looked at past weather records and used computer models to compare this month’s weather to a scenario where there was no human-caused climate change of 1.3 degrees Celsius (or 2.3 degrees Fahrenheit) that has occurred since industrial times. This helped them figure out how much heat caused the disaster. It’s a method that the National Academy of Sciences approves as reliable. Although these quick studies haven’t been reviewed by experts yet, most of them later appear in peer-reviewed papers without major changes, according to Friederike Otto, a leading scientist at World Weather Attribution.
“The number (35%) doesn’t sound like much” because, unlike dozens of its past studies, the team looked at a small area and a complex meteorological measurement in the fire weather index that would generally mean there would be large uncertainties, said Otto, a climate scientist at Imperial College London. In this case, the signs of climate change are strong enough to be noticeable, she said.
Those conditions are part of what makes California attractive to 25 million people, said study co-author John Abatzoglou, a climate and fire scientist at the University of California Merced.
Southern California has one of the best climates and weather in the world, except when certain elements come together, said Abatzoglou. “You have a combination of dry, windy, and warm weather.” When dry materials and sparks are added to those three factors, it creates the right conditions for fire disasters.
Abatzoglou explained that several factors must come together, like dust, fuel, high temperatures, wind, and sparks, for fires to start and grow.” Imagine switches for a light bulb that makes it shine better. Co-author Park Williams, a climate and fire scientist at UCLA, said that human-caused climate change is like turning up those switches, making the world warmer.
The study found that California’s dry season is now 23 days longer. It also showed that there is more than twice the chance of not having rain in October, November, and December compared to before industrial times. However, the researchers couldn’t link these changes to climate change or the specific fires happening this month due to data limitations, according to Otto. She said, “The rain is getting less because of climate change caused by humans.”
Then add in strong winds to whip and spread fire.
Mike Flannigan, a Canadian fire expert not involved in the study, pointed out that a major concern is the fire season lasting longer, which raises the likelihood of fires starting during the strong Santa Ana winds.
The study could not measure how much, if at all, climate change impacted the Santa Ana winds.
Craig Clements, a climate scientist and the head of wildfire research at San Jose State University, stated that the quick study is reasonable and aligns with previous research on other fires.
Clements, who wasn’t involved in the study, said, “It’s difficult to link every fire to climate change, as many people do.” “If we are sure that climate change is causing the drought, then that is the evidence.”
If the world heats up by another 1.3 degrees Celsius, the study says people can expect the weather that caused these fires to occur 35% more often.
Otto said this is about science, not politics.
“You can’t say that this happened just because California made a big mistake.” They did many things well. “They did some things that they could improve,” Otto said. “But what makes these fires even more dangerous is human-caused climate change, something that the California government cannot control on its own.” And drill, baby drill will make this much, much worse.”
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