Projected Increases in fire weather days even when the Paris Agreement targets are met: an exploration of fire risk uncertainty with a perturbed physics ensemble of climate models 

Large destructive fires can cause extensive damage to ecosystems, and infrastructure, and loss of life. Understanding how these ‘wildfires’ are likely to change as the world warms is vital for effective fire management planning. This study provides information on likely future change and associated uncertainty in fire weather, relevant for fire management planning, including periods and extent of extreme fire weather and length of control burn season.  We use the McArthur Forest Fire Danger Index (FFDI) to investigate the effect of human-caused climate change on fire weather. We use a large, perturbed physics ensemble to explore the uncertainty at three Global Warming Levels (GWLs); 1.5°C, 2.0°C and 4.0°C above pre-industrial temperatures, for two emissions scenarios, RCP2.6 (a mitigation scenario), and RCP8.5, (a high-end scenario). We look globally, and focus on three regions: Australia, Brazil and the USA.  The frequency and severity of fire weather increases at all GWLs. The amount of land with more fire weather days increases with GWL, as does the uncertainty. Limiting warming to 1.5°C limits increases in future fire weather. However, even at 1.5°C, there is still a 31% (25% – 36%) increase in the land surface with more fire weather.  Our analysis shows a substantial increase in fire weather and shortened control burn season even under the best-case scenario of meeting the 1.5°C Paris Agreement temperature target. However, exceeding the Paris Agreement target will see a much more substantial increase in both the fire season length and the amount of the land surface exposed to a greater risk of wildfires. These potential changes in fire weather have important implications for planning appropriate responses, such as the controlled burning season length, resourcing and training of fire managers and first responders, and the development of fire management plans.