Rapid warming has resulted in more wildfires in northeastern Australia

Wildfires, or bushfires, are one of the most destructive natural disasters in Australia, which can cause many deaths of stock, native animals, sometimes humans, and huge impacts on infrastructure. Reconstructing past wildfires and exploring the links between wildfires and climate are essential for understanding the dynamics of wildfires and for predicting future risks. In this study, the frequency of wildfires in northeastern Australia over the past 25,000 years was reconstructed from the charcoal records preserved in peat and lake sediments. The results showed that the frequency of wildfires were relatively low during the cool last glacial period and the warm mid Holocene, indicating that the stable mean climate conditions, whether cool or warm, would not independently initiate increased wildfires in northeastern Australia. The most frequent wildfires occurred during the last deglaciation period, when Earth's climate warmed and the warming rate was the highest over the last 25,000 years, before recent anthropogenic warming. It suggested that the rapid global warming may greatly increase the likelihood of dangerous wildfires in northeastern Australia during the last deglaciation. The wildfires reactivated over the most recent 4000 years, coinciding with amplified climate variability and probably an expansion of human activity. The rapid warming of global climate during the last deglaciation period is an ideal analogue for current anthropogenic global warming. The comparison between fire count and temperature changes in Australia since 2003 also showed that the fire frequency in Australia in recent years is more closely correlated with the warming amplitude, rather than mean temperature. Our results implied that the wildfire risk in northeastern Australia may increase further under the expected accelerating global warming, if human management systems does not intrude. Wildfire modeling could benefit greatly by considering the relationship of fires with climate variability rather than only with stable climate scenarios.