Chile and Argentina’s wildfire emergencies in recent weeks were fueled not only by hot, dry and windy weather but also by human-caused climate change, according to a new assessment led by the World Weather Attribution scientific initiative.
The team said the unusually dangerous conditions that fed deadly fires in central and southern Chile—temperatures, dryness and gusty weather—were made up to three times more likely than they would have been without global warming. In southern Argentina, the researchers said the conditions that supported widespread burning were made about 150% more likely by human-caused greenhouse gas emissions.
“Overall, we’re confident in saying that the main driver of this increased fire risk is human-caused warming,” Clair Barnes, a research associate with World Weather Attribution, said during a briefing. Barnes added that those trends were projected to continue as long as fossil-fuel burning continues.
The fires described in the assessment followed severe weather and combustible landscapes. In Chile, blazes in the Biobío and Ñuble regions in mid-January killed 23 people, destroyed more than 1,000 houses and other structures, and forced tens of thousands to flee, according to the assessment. The fires were ignited by human activity, the report said, whether through arson or negligence.
In southern Argentina, fires initially sparked by lightning forced evacuations of thousands of tourists and residents and burned through more than 45,000 hectares (174 square miles) of native forest, including swaths of the Los Alerces National Park, a UNESCO World Heritage site known for 2,600-year-old trees.
The assessment, while consistent with expectations from longer-running climate modeling, also provided what it said was the first scientific assessment of global warming’s role in intensifying major wildfire emergencies in the two countries. World Weather Attribution said the analysis was not yet peer-reviewed or published in a scientific journal, though it relied on methods the initiative described as widely accepted, including comparing today’s climate with past weather patterns using data and computer model simulations.
Carolina Vera, a professor of climate sciences at the University of Buenos Aires who was not involved in the World Weather Attribution work, said the findings matched earlier research on how warming affects wildfires, particularly in the native forests of Argentina’s Chubut province where she lives. Vera said in her view “this particular fire case” shows anthropogenic climate change “dominating over other factors,” and she pointed to the role of extreme heat and strong winds in enabling fast spread across Patagonia’s native forests.
Another outside scientist, Dominique Bachelet of Oregon State University, said the results did not surprise her. Bachelet pointed to climate model projections made over more than two decades about increasing fire danger, including effects through deeper droughts, shifts in prevailing wind patterns, and changes to the timing and length of seasons.
The World Weather Attribution team said the underlying fuel conditions also mattered. It found that record drought and high temperatures created wildfire-friendly settings in both Chile and Argentina, and that in the region, single-species plantations of highly flammable trees such as pines helped the fires spread more easily. The assessment said invasive species have replaced native, more fire-resistant ecosystems, leaving shrub, brush and grass as “kindling.”
The researchers also described unusually warm and dry extremes in Argentina. Some weather stations in Patagonia that have been operating for about 70 years recorded heat waves they characterized as unprecedented in duration and severity, including a record high in El Bolsón of 38.4 degrees Celsius (101 degrees Fahrenheit) in January. Near Los Alerces National Park, the town of Esquel recorded 11 consecutive days of maximum temperatures in January, their second-longest warm spell in 65 years.
In Chile, the researchers said temperatures were high before the fires started but did not reach record levels. They estimated that seasonal rainfall from November through January—before the main burning period—was about 25% weaker in Chile and about 20% less intense in Argentine Patagonia than it would have been without warming of at least 1.3 degrees Celsius (2.3 degrees Fahrenheit) since pre-industrial times.
Juan Antonio Rivera, an author of the study from Argentina’s National Scientific and Technical Research Council, said the combination of weaker rainfall and higher-than-average temperatures put vegetation under stress, lowered soil humidity, and left enough fuel for the fires to extend and persist once they began.
Alongside climate and fuel conditions, the researchers said differences in resources for firefighting and response may affect how badly communities are hit. They said Chile increased its wildfire-fighting budget by 110% over the last four years under left-wing President Gabriel Boric, including investments meant to improve forecasting and new equipment. In Argentina, the assessment pointed to challenges tied to austerity measures under libertarian President Javier Milei, including budget cuts for firefighting crews and reduced planning, along with deregulation affecting tourism activities in Patagonia’s national parks—claims the assessment said were echoed to The Associated Press by firefighters, park rangers and officials involved in relief.
Milei, like his ally U.S. President Donald Trump, has denied that climate change is related to human activity, according to the report. His office did not respond to a request for comment Wednesday.
Rivera said the situation can worsen when governments do not treat climate change as linked to human activity. “Unfortunately, with a government that does not understand climate change and its connection to human activities, where nature is secondary in terms of priorities, these situations get worse and wildfires end up having greater impacts than they should,” Rivera said. “The situation is still not under control.”