Preprints
https://doi.org/10.5194/nhess-2019-206
https://doi.org/10.5194/nhess-2019-206

  13 Aug 2019

13 Aug 2019

Review status: this preprint was under review for the journal NHESS. A revision for further review has not been submitted.

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

Folmer Krikken1, Flavio Lehner2, Karsten Haustein3, Igor Drobyshev4,5,6, and Geert Jan van Oldenborgh1 Folmer Krikken et al.
  • 1Royal Netherlands Meteorological Institute (KNMI), De Bilt, Netherlands
  • 2National Center for Atmospheric Research, Boulder, USA
  • 3Environmental Change Institute, University of Oxford, Oxford, United Kingdom
  • 4Centre for Forest Research, Montreal, Canada
  • 5NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management Universite du Quebec, Canada
  • 6Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Alnarp, Sweden

Abstract. In this study we analyse the role of climate change in the forest fires that raged through large parts of Sweden in the summer of 2018 from a meteorological perspective. This is done by studying the Canadian Fire Weather Index (FWI) based on sub-daily data, both in reanalysis datasets (ERA-Interim, ERA5, JMA55 and MERRA2) and three large ensemble climate models (EC-Earth, W@H and CESM) simulations. The FWI based on reanalysis correlates well with observed area burned in summer (r = 0.6 to 0.8). We find that the maximum forest fire risk in July 2018 had return times of ∼ 24 years for Southern and Northern Sweden. Further, we find a negative trend of the FWI for Southern Sweden over the 1979 to 2017 time period, yielding a decreasing risk of such an event solely based on reanalysis data. However, given the short observational record, large uncertainty between the reanalysis products and large natural variability of the FWI we cannot draw robust conclusions from reanalysis data.

The 3 large-ensembles with climate models on the other hand point to a roughly 1.1 times increased risk for such events in the current climate relative to pre-industrial climate. For a future climate (2C warming) we find a roughly 2 times increased risk for such events relative to pre-industrial climate. The increased fire weather risk is mainly attributed to the increase in temperature. The other main factor, precipitation during summer months, is projected to increase for Northern Sweden, and decrease for Southern Sweden. We however do not find a clear change of prolonged dry periods in summer months that could explain the increased fire weather risk.

In summary, we find a small but positive role of global warming up to now in the 2018 forest fires in Sweden, but a more robust increase in the risk for such events in the future.

Folmer Krikken et al.

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Folmer Krikken et al.

Folmer Krikken et al.

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Short summary
In this study we analyse the role of climate change in the forest fires that raged through large parts of Sweden in the summer of 2018 from a meteorological perspective. This is done by studying observational constrained data and multiple climate models. We find a small but positive role of climate change up to now in the 2018 forest fires in Sweden, but a more robust increase in the risk for such events in the future. This is mainly caused by the higher temperatures projected in future climate.
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