Risk of forest fire in Sweden under historical and future climate projections from 1971 to 2100t fire in Sweden under historical and future climate projections from 1971 to 2100

With the large forest fire in Sala 2014 and the forest fires during summer 2018 in mind, evaluating the tendency of high-risk fire season (HRS) under a changing climate shows its importance for risk management.

This study focuses on exploring the behaviours of several user-defined fire-risk indicators concerning start, end, length, HRS and frequency of HRS, and impact of preconditions, e.g., snow cover and overwintering conditions. Here, we carry out the study by driving a Canadian forest fire model, the Fire Weather Index (FWI, Van Wagner,1987), using meteorological forcing from an ensemble of regional climate projections compiled from the Coupled Model Intercomparison Project Phase 5 (CMIP5, Taylor et al., 2012). The used CMIP5 data covers historical and representative concentration pathway projections (RCPs) from 1971 to 2100. The bias in the climate model projections is adjusted using the MultI-scale bias AdjuStment (MIdAS, Berg et al., 2022) with Copernicus regional reanalysis for Europe (CERRA, Schimankes et al., 2021) as a reference. The impact of climate change on the fire risk for three future periods (i.e., 2011–2040, 2041–2070 and 2071–2100) is explored under three RCPs (RCP2.6, 4.5 and 8.5).  The ensemble agreement is used to evaluate the robustness of the fire risk indicators. 

The results show that all robust changes are toward increasing risk. More specifically, the length of HRS increases in southern and eastern Sweden. The start of HRS shifts to earlier in the eastern coastal and northern regions of Sweden in RCP4.5 and 8.5. In all RCPs the end of HRS is delayed by a couple of weeks in the southern regions in the period after 2041. The HRS is likely to become more frequent in the regions along the east coast and in southern Sweden.