In the past 35 years, wildfire season duration has increased by almost 20% according to a study published in Nature Communications. The research finds that all vegetated continents except Australia are affected by this increase.

Wildfires burn approximately 350 million hectares each year, resulting in social disruption and substantial economic loss. Over the past decade, the USA has spent $1.7 billion dollars on wildfire suppression alone. A surge of extremely destructive wildfires in recent years has led to calls for a greater understanding of the drivers behind wildfire activity, with many proposing a link to climate change. William Jolly and colleagues analyse fire season length over the last 35 years using a novel ensemble of three widely used fire danger indices, formulated from three daily global climate datasets. These integrate the key drivers of fire: wind, humidity, temperature and precipitation. The authors’ find that combined surface weather changes have resulted in the duration of fire seasons increasing by 18.7%, so that it now affects more than a quarter of the globe’s vegetated land surface.