Climate Change Increases the Potential for Extreme Wildfires

Pyrocumulonimbus (pyroCb) wildfires cause devastation in many regions globally. Given that fire-atmosphere coupling is associated with pyroCbs, future changes in coincident high index values of atmospheric instability and dryness (C-Haines) and near-surface fire weather are assessed for southeastern Australia using a regional climate projection ensemble. We show that observed pyroCb events occur predominantly on forested, rugged landscapes during extreme C-Haines conditions, but over a wide range of surface fire weather conditions. Statistically significant increases in the number of days where both C-Haines and near-surface fire weather values are conducive to pyroCb development are projected across southeastern Australia, predominantly for November (spring), and less strongly for December (summer) in 2060-2079 versus 1990-2009, with future C-Haines increases linked to increased 850-hPa dewpoint depression. The increased future occurrence of conditions conducive to pyroCb development and their extension into spring have implications for mitigating these dangerous wildfires and urbanizing fire-prone landscapes.