Climate change has increased the odds of extreme regional forest fire years globally

In the past decade, regions across the globe have experienced devastating fire years with far-reaching impacts including direct harm to communities, hazardous air quality, and high carbon emissions. We examine the role of antecedent and concurrent climate variability in enabling extreme regional fire years – herein defined as years with the highest forest burned area during 2002-2023 – across global forested lands. Extreme regional fire years typically coincided with years with extreme seasonal fire weather indices (FWI) and had an average four-fold increase in the number of very large fires emitted more than five-times the fire carbon emissions than non-extreme years. A majority of extreme regional fire years co-occurred with FWI metrics exceeding a 20-yr return period, whereas weaker FWI links were seen in the tropics where land-use and deforestation likely confound relationships. We show that the likelihood of FWI metrics exceeding a 20-yr return period is 50-150% higher for much of the globe under a contemporary (2011-2040) climate compared to a preindustrial (1861-1890) climate. These results suggest that human-caused climate change has augmented the odds of recent and near-term extreme climate-driven fire years across forested regions of the globe. While variability in fire years stems from the interplay of biophysical and societal factors, the exacerbating effect of climate change underscores the urgent need for proactive measures in mitigating risks and adapting to these extreme fire years.