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Drier-than-normal conditions that fuelled wildfires in Chile and Argentina were made 2.5 to three times more likely by climate change, a World Weather Attribution study finds
The affected regions are now experiencing 20–25% less rainfall than in a world without fossil fuel emissions
Fires destroyed homes, displaced tens of thousands and threatened ancient Alerce trees in a UNESCO-listed national park
Scientists say rising temperatures, drought, La Niña and flammable pine plantations intensified the fire risk
The drier-than-normal weather conditions that fuelled devastating wildfires earlier this year in Chile and Argentina — putting at risk some of the planet’s oldest trees — were made between 2.5 and three times more likely by global warming, according to an analysis by the World Weather Attribution (WWA) consortium.
WWA, a global network of climate scientists, conducts ‘attribution studies’ to understand and quantify the role of human-induced climate change in the occurrence, frequency and intensity of extreme weather events.
The researchers found that the affected regions are now experiencing “between 20-25 per cent less rainfall than they would have in a world without the burning of fossil fuels”. Weak La Niña conditions also contributed to the unusually dry weather, the study said.
In the first week of January 2026, wildfires broke out in Argentina’s Chubut province in Patagonia, engulfing parts of the Los Alerces National Park listed under the United Nations Educational, Scientific and Cultural Organisation (UNESCO). The park is home to ancient Alerce trees that can live for more than 3,000 years.
A few weeks later, between January 17 and 19, wildfires ignited in Chile’s Biobío and Ñuble regions. Around 1,000 homes were burned, about 52,000 people were forced to flee and 23 people were killed. By January 23, approximately 64,000 hectares had been consumed and a state of emergency was declared.
The fires were driven by maximum temperatures exceeding 37 degrees Celsius (°C) and wind speeds above 40 kilometres per hour, combined with months of drought. Parts of central-southern Chile have endured a prolonged drought since 2010 — and according to some estimates, since 2007.
In Argentina, fires intensified again around January 27, spreading through forested valleys and lake districts near Cholila, Puerto Patriada, El Hoyo, El Bolsón, Lago Puelo and Los Alerces National Park, according to the WWA. A state of emergency was declared on January 29 as another 45,000 hectares were burned.
As of the second week of February, some regions were still battling active fires. “At the time of writing, the fires were still ongoing, with new major events reported in the ancient forests of the UNESCO World Heritage site Los Alerces National Park,” the WWA said.
Scientists used the Hot-Dry-Windy Index (HDWI) to analyse the causes of the fire weather and their attribution to warming and consequent climate change. The HDWI combines data on wind speeds, temperatures and humidity to ascertain the probability of the occurrence of wildfires in any particular region.
“While not taking the build-up of fuel into account like other, more complex indices, it is an effective hazard metric for estimating threat to communities and difficulty of containment,” the authors wrote.
In Chile, the study region covered the area between the coast and the foothills of the Andes in the Biobío, Ñuble and La Araucanía regions. The HDWI was analysed over a two-day event. In Patagonia, near the Chile-Argentina border, the analysis covered five days.
Observational data suggested that the wildfires were roughly once-in-five-year events in today’s climate. When combined with climate modelling, researchers concluded that such events would have been significantly rarer in a world without greenhouse gas-driven warming.
The Chilean fires were made three times more likely by human-induced warming, while the Patagonia fires were made 2.5 times more likely, the study found.
The researchers also documented a marked decline in rainfall in the affected regions.
“Combining observation-based data products and climate models we find that fire-season rainfall intensity has decreased by about 25 per cent in the Chilean region and by about 20 per cent in the Patagonia region,” the study said.
At the same time, unusually high temperatures led to increased evapotranspiration, leaving vegetation drier and more combustible.
Natural climate variability also played a role in increasing the risk. La Niña, a cooling pattern in the equatorial Pacific Ocean, tends to shift rainfall away from the region. The Southern Annular Mode (SAM) — influenced by pressure differences between 40°S and Antarctica (65°S) — further contributed to the development of high-pressure systems, reinforcing hot and dry conditions in the region.
SAM affects the position and strength of southern westerly winds, which in turn shape weather patterns across much of the southern hemisphere.
The study also pointed to the role of vegetation type in aiding the blaze. “In both regions, non-native needleleaf trees contributed to elevated wildfire risk. Monocultural pine (Pinus radiata) plantations are highly flammable, due to uninterrupted similar fuel structure, dense tree stands, and species flammability,” the report noted.
“Early removal of invasive pines is therefore critical to prevent landscape-scale increases in fire hazard,” it added.
Juan Antonio Rivera, a WWA author from the Argentine Institute of Nivology, Glaciology and Environmental Sciences (IANIGLA), Scientific and Technological Center (CCT) — CONICET in Mendoza, in a statement, said the fires were striking at the heart of communities and natural heritage. “In Patagonia, we are seeing blazes threaten the Alerce trees — ancient giants that have stood undisturbed for thousands of years,” he said.
“For Chile and Argentina, the drying of our landscapes is no longer a projection, but a crisis that needs an urgent response to protect our unique biodiversity and the people of our region,” Rivera added.