Attribution of the role of climate change in the forest fires in Sweden 2018

This is done by studying the Canadian Fire Weather Index (FWI) based on sub-daily data, both in reanalysis data sets (ERA-Interim, ERA5, the Japanese 55 year Reanalysis, JRA-55, and Modern-Era Retrospective analysis for Research and Applications version 2, MERRA-2) and three large-ensemble climate models (EC-Earth, weather@home, W@H, and Community Earth System Model, CESM) simulations.

The FWI, based on reanalysis, correlates well with the observed burnt area in summer (r = 0.6 to 0.8). We find that the maximum FWI in July 2018 had return times of similar to 24 years (90% CI, confidence interval, > 10 years) for southern and northern Sweden. Furthermore, we find a negative trend of the FWI for southern Sweden over the 1979 to 2017 time period in the reanalyses, yielding a non-significant reduced probability of such an event.