Climate-driven emergence of fire danger in South America under global warming

Abstract This study assesses the capability of ten Coordinated Regional Climate Downscaling Experiment regional climate models to simulate the components of the Canadian fire weather index (FWI) system across South America. Model performance for the historical period (1951–2005) is evaluated against the Copernicus Emergency Management Service ERA5 reanalysis using correlation, root mean square error, bias, and inter-model variability as validation metrics. Future projections are analyzed using the time of emergence and global temperature of emergence frameworks under two representative concentration pathways (RCP4.5 and RCP8.5), to identify when and under which global warming levels fire-conducive conditions emerge beyond natural variability. Results show that FWI and the fine fuel moisture code reproduce observed variability most accurately ( r > 0.70), while cumulative indices such as the drought code and Duff moisture code exhibit larger uncertainties linked to precipitation biases and long-term moisture processes. Projections indicate that extreme fire weather conditions (represented by the frequency of days exceeding the 95th percentile of FWI, FWI95d) emerge earliest and most extensively, particularly under the high-emission RCP8.5 scenario, with large areas of northern and central South America crossing emergence thresholds during the early years of the 2030s decade. In contrast, indices related to fire-season length (FWIfwsl) and seasonal severity (FWIfs) show delayed and spatially fragmented emergence patterns, reflecting their stronger dependence on persistent warming trends. A critical finding is that several regions, including southern Brazil, Paraguay, northern Argentina, and Bolivia, have already exceeded emergence thresholds during the historical period, signaling that shifts in fire-weather regimes are already underway. These results highlight the urgent need to strengthen fire management and adaptation strategies across South America, while emphasizing that limiting global warming below 2 °C would significantly delay and reduce the extent of emerging fire danger in the region.