Has the fire weather index emerged? Insights from global and regional climate models

Wildfires are expected to become more intense due to global warming. This change will significantly affect ecosystems and communities. We examine when and where fire weather conditions go beyond natural variability by using the Canadian Fire Weather Index (FWI). We analyze data from CORDEX-CORE and EURO-CORDEX regional simulations, along with CMIP5 and CMIP6 global models, under the RCP8.5 and SSP5-8.5 scenarios. The study spans from 1980 to 2099 and focuses on Global Warming Levels (GWLs) ranging from +1.5 to +4.0 °C compared to pre-industrial climate. When we evaluate against GEFF-ERA5 reanalysis, we find that the CORDEX ensemble better reflects historical FWI trends compared to CMIP5 and CMIP6. Projections show widespread increases in FWI, primarily due to higher temperatures and lower relative humidity, along with regional impacts from precipitation and wind. The danger class analyses indicate a shift toward Extreme and Very Extreme conditions in the Mediterranean, southern Africa, South America, and Australia, occurring already with 2–3 °C of warming. The Time of Emergence (ToE) analysis reveals that human influence is already detectable in 39% of the AR6 regions, to become 81% by 2030. The Global Temperature of Emergence (GToE) suggests that over 25% of burnable land areas will cross emergence thresholds at +1.5 °C, increasing to over 70% at +3.0 °C. The length of the fire season is also expected to increase in most regions. These findings highlight the urgent need for strategies to manage wildfire risk and adapt to these changes globally.