As of March 2023, Canada has been burning for eight months, with flames ripping through all 13 provinces and territories in the country’s deadliest fire season ever. At least 150,000 evacuate people, and tens of millions across North America was affected by the drifting smoke. In New York, residents experienced the worst air quality in half a century.
Five months later, Greece was besieged by the European Union’s largest fire yet, which claimed nearly 350 square miles of forest and claimed the lives of 19 immigrants. Near the equator, the Amazon has experienced a record number of fires. for months, satellite images showed thick plumes of smoke enveloping entire fields and tracts of charred land, their outline accentuated by flares of highlighter-orange flames.
We can thank climate change for these unprecedented fires. On Tuesday, an international group of scientists released Status of wildfiresan annual report that analyzed global wildfires between March 2023 and February 2024, concluding beyond doubt that climate change has intensified the conditions that fueled the flames. According to the report, last year’s wildfires in Canada, Greece and the Amazon were at least three times more likely – and up to 20 times more likely – than they would have been without human-caused planetary warming.
The scientists also found that all this burning produced a staggering 8.6 billion metric tons of carbon dioxide – 3 billion more than the US emitted from burning fossil fuels in 2022.
“This release of greenhouse gases … creating a positive feedback loop that can then lead to more extreme fires,” said Douglas Kelley, a fire expert at the UK Center for Ecology and Hydrology and one of the authors of the report. “So if we continue to put out greenhouse gases in the same way we are now, we will see at least six to 11 times more of those fires by the end of the century.”
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To understand how the changing climate has stacked the odds, the researchers analyzed regional data to identify changes in fire weather—a term that describes the hot, dry, and often windy conditions in which wildfires can easily start. Climate and ecological factors, such as changes in rainfall or overgrowth of plants, can make environments more flammable. Add to drought and heat wavesboth of which are exacerbated by climate change, and firefighting becoming more extreme.
But these conditions only mean that a large fire can easily ignite and spread – not that it necessarily will. According to Kelley, even with a good understanding of risk, predicting the next extreme fire remains a tricky business, in part because human behavior can make a big difference.
“People go out and start fires, or they can put out fires,” Kelley said. “And while climate change has led to changes in fires, so has human fragmentation of the landscape.” In some places, agriculture and roads prevent fires from spreading that far. In others, deforestation can make forests drier and provide fuel so they can burn more. And in the US, decades of bad forest management have paved the way for extreme fires by suppressing naturally occurring fires, leaving the landscape a tinderbox of overgrown vegetation.
Because each area is uniquely complex, the researchers focused their analysis on three distinct regions that had large wildfires with robust data available: Canada, Greece and the Amazon.
In Canada, the burning of more than 50,000 square miles of boreal forest spewed out about a quarter of the world’s total CO2 emissions in the year-long study period. Overall, the report found that the warming planet is making Canadian fires three times more likely. But the researchers also note that if Canada’s landscape had not been altered by humans, through agriculture, fire management and urban infrastructure, the damage would have been even more widespread. In Greece, similar factors prevented the 2023 Evros fire from being worse than it was.
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Of all the regions examined in the report, the rainforests of Amazonia – covering Brazil’s Amazonas state and neighboring parts of Bolivia, Peru and Venezuela – appear to bear the greatest impact from climate change. Here, the researchers found a 20 times greater likelihood of severe wildfires. And in 2023, a particularly strong El Niño, a multi-year climate pattern influenced by the cycling of warm ocean currents, contributed to a record-breaking fire season.
“El Niño makes it harder for rain to form in the Amazon, causing drier and warmer weather,” said Maria Lucia Barbosa, a fire researcher at the University of São Carlos, Brazil, and one of the authors of the study. “When people use fire, it spreads easily under these conditions.” According to the report, the fires have also come at a great cost to dozens of indigenous nations living in the area, who depend on a healthy forest for their livelihoods.
The State of Wildfire report also discussed damage from other notable fires during the study period, although not in the same depth. In Hawaiʻi, the town of Lahaina was destroyed in a August inferno which took 102 lives. In Australia, more than 300,000 square miles burned through the Southern Hemisphere’s summer – making it the largest bushfire season in more than a decade. In Chile, hundreds of fires broke out in the midst of a megadrought. Globally, the report found that climate change is making extreme fires twice as likely. A separate analysis of satellite data released in June found that extreme wildfires have become twice as frequent and intense over the past two decades.
“In our lived experience, we’re seeing things that were predicted decades ago,” said Maureen Kennedy, an associate professor of fire ecology at the University of Washington, Tacoma, who was not involved in the State of Wildfires report. She says the report’s findings are consistent with what she considers “classic features” of a warming planet.
“Climate change is loading the dice in favor of extreme firefighting that makes wildfires very difficult to fight and really difficult to suppress,” she said.
Although State of Wildfire researchers have found that the likelihood of such extremes will continue to rise through the end of the century, Kelley and McNorton say humanity still has time to create a better outcome.
“I think that’s the hopeful, if not slightly scary, part of the future projections,” Kelley said. Although there will still be an increase in extreme fire, no matter how much we limit our emissions, it is still possible to limit how severe the situation becomes, he said.
