The future of extreme meteorological fire danger under climate change scenarios for Iberia

Wildfires are disturbances that occur in ecosystems, both naturally and derived from anthropogenic factors, often caused by extreme meteorological conditions, and have recurrently destructive impacts on forests throughout the world. The complex nature of the interactions between wildfires, their dynamics, and human interference from a climate change perspective has motivated a growing number of researchers to address this topic. The fire weather index (FWI) has been extensively used to analyze the link between meteorological fire danger and its local to regional characteristics contributing to the severity of these events, as well as real-time operational monitoring at national and international levels. Recently, a new improved fire danger index that includes the effect of atmospheric instability has been developed, the so-called FWIe. The presence of instability in the atmosphere may be a boost to more energetic wildfires, such as the June 2017 extreme event in central Portugal, making it an important asset in risk monitoring and management. Here, a comprehensive examination of future fire risk on the Iberian Peninsula was performed. Additionally, a comparative analysis between FWI and FWIe was pursued in the context of climate change. We computed both FWI and FWIe using a multi-model ensemble composed of 13 Euro-CORDEX Regional Climate Model (RCM) simulations forced by different global climate models. The historical period (1971-2000) and three projected periods of 30 years (2011-2040, 2041-2070, and 2071-2 100), under three emission scenarios (RCP2.6, RCP4.5, and RCP8.5) were considered. When assessing modelled FWI and FWIe, results show that summer values tend to substantially increase in the future when assuming the historical period as the benchmark, with an expected extension of the danger period to June and, in a lower magnitude, to September. The north-western region of Iberia, including the north of Portugal and the northwestern-to-central Spain are the regions with larger increases in danger in the future, which may be critical since these are the regions with more fire-prone vegetation. This work also points to large differences in fire danger projections among scenarios, calling for a distinct set of adaptation needs that should be timely prepared by stakeholders and authorities.