A recent study highlights a troubling trend: the wildfire seasons in Australia and North America are increasingly overlapping due to climate change. Dr. Doug Richardson heads up the research that shows just how extreme this trend is by looking at days with fire weather warning since 1979. This trend has huge consequences for firefighting in both regions. The research was published in the American Geophysical Union’s journal Earth’s Future. It includes climate science contributions from Dr. Andreia Ribeiro and Prof. Dr. Jakob Zscheischler.
Together, our findings paint a disturbing picture. Areas that historically had clear summer and winter fire seasons—such as the west coast of North America and the east coast of Australia—are experiencing exacerbated fire risk during those extended months. This overlap presents complications for firefighting tactics and foreign assistance during wildfire emergencies.
Overlapping Fire Weather Seasons
In the past, fire seasons in North America and Australia were mirror images of one another, flaming up opposite sides of the globe. For the east and west coasts of North America, these transects afforded an extended fruiting season from June to October. By contrast, eastern Australia experienced its government’s fire season from October to March. This trend has changed completely in recent years.
Observational data indicate that the count of concurrent fire weather days across both of these regions has risen dramatically. In the past 40 years, it’s gone up a full day per year. Above, SEA staff scientist Dr. Andreia Ribeiro addresses a group on the earlier onset of fire season in Eastern Australia. This shift coincides with the conclusion of fire season on the west coast of North America.
“This is because the fire season in eastern Australia is starting earlier in spring and overlapping with the end of the fire season on the west coast of North America,” – Dr. Andreia Ribeiro
The highest chance of overlap occurs from July through December. During these months, the risk of wildfires is at its highest at about 75%. As the research shows, climate models predict an increase in fire weather days. By mid-century, that might jump to 4 to 29 more days per year, given where we end up on global warming temperature targets.
The Role of Climate Change and El Niño
According to the study, climate change is not a secondary cause, but rather the most important driver of these converging fire seasons. The first, prof. dr. Jakob Zscheischler, is claiming that El Niño events have always caused changes in weather. Yet, in the medium term, their beneficial effects will be completely eclipsed by larger-scale changes due to climate.
“Climate change is causing global temperature rises and increasing drought in some regions while the El Niño effect is expected to remain largely unchanged,” – Prof. Dr. Jakob Zscheischler
Fire weather in eastern Australia is usually associated with El Niño years, marked by abnormally warm sea surface temperatures. Fire weather in western North America is more often associated with the opposite — La Niña, which indicates cooler ocean temperatures. Dr. Ribeiro notes that high fire weather overlap tends to happen in years with pronounced El Niño conditions. That’s particularly true in the Central Pacific.
“Despite these generally opposing patterns, we found that during strong fire weather overlap, El Niño conditions are especially pronounced in the Central Pacific,” – Dr. Andreia Ribeiro
Implications for Firefighting Strategies
The consequences of this research go well beyond the ivory tower. They highlight the adaptation to climate change that firefighters require—yesterday. Australia and the United States need to strengthen their ground constituency for firefighting. This need is compounded at a time when international cooperation is becoming scarcer, due in part to cascading wildfire seasons.
Dr. Doug Richardson highlights this concern, stating that the increasingly overlapping fire weather seasons hinder effective international collaboration during large-scale wildfire incidents.
“But these increasingly overlapping fire weather seasons in the US and Australia are narrowing the window for international cooperation and making it harder to respond quickly to large-scale wildfires,” – Dr. Doug Richardson
We know climate change is already changing the world’s weather patterns. No matter the path forward, regions need to prepare for a future where the threat of wildfires is increasing. The research provides important information for public policy leaders and emergency management organizations. Most significantly, it underscores the critical need to adopt preemptive, forward-looking approaches that ensure better firefighting resources and strategies.