Scientists warn that longer fire seasons in Australia and North America are overlapping due to climate change, challenging international emergency cooperation.
Fire risk rising with the climate
As global temperatures rise, wildfires are becoming more frequent, intense, and unpredictable. A new international study by scientists from Germany’s Helmholtz Centre for Environmental Research (UFZ) and Australia reveals that fire weather seasons in eastern Australia and western North America are increasingly overlapping largely due to climate change. This shift threatens the long-standing mutual aid system between fire services in Australia the United States and Canada. The findings were published in the journal Earth’s Future.
January 2025 LA wildfires past Australia bushfires show the cost
Recent disasters show the growing danger. In January 2025, wildfires in Los Angeles destroyed over 10,000 buildings and claimed 29 lives. Similarly between September 2019 and March 2020, eastern Australia witnessed one of its most devastating bushfires with more than 12 million hectares burned. Historically these regions have sent firefighters and equipment to each other during fire seasons. That may no longer be possible.
Tracking fire weather with science
To study the changing risk, researchers used the Canadian Fire Weather Index (FWI) a widely accepted system that calculates daily wildfire risk based on temperature, humidity, wind speed, and rainfall. From 1979 to today, the study found that the number of overlapping fire weather days has risen by one day per year. The greatest overlap about 75% occurs between July and December when both regions are vulnerable to large-scale fires.
Climate models predict worsening overlap
Lead author Dr. Andreia Ribeiro explained that the fire season in eastern Australia is starting earlier, now overlapping with the tail end of North America’s fire season. Using four climate models, researchers estimate that if warming continues, the number of overlapping fire weather days could rise by 4 to 29 days annually by mid-century.
What’s driving the change? El Niño, La Niña, and climate change
Typically El Niño brings drought and fire risk to Australia, while La Niña is linked to fires in western North America. Surprisingly, researchers found that during years of maximum overlap, El Niño conditions were unusually strong in the Central Pacific. Still, scientists say the long-term impact of climate change is surpassing natural climate cycles, making fire seasons longer, drier, and hotter.9
Firefighting alliances under threat
This overlap challenges the cooperation system between Australia the US, and Canada. These countries have historically shared personnel, aircraft, and resources, relying on seasonal gaps between fire periods. Now, those gaps are disappearing. “It’s narrowing the window for international cooperation,” said Dr. Doug Richardson, co-author from the University of New South Wales.
Conclusion: Rethinking fire strategies for a warming world
With climate change accelerating the overlap of fire weather seasons, the world’s firefighting strategies are due for urgent updates. Nations can no longer count on international help arriving just in time. As climate-driven fire risk intensifies, the study urges governments to strengthen domestic firefighting capacity, revise international agreements, and prepare for simultaneous large-scale wildfire emergencies.