Sixty Years of Increasing Wind Storm Damages in European Forests

In Europe, studies of historical large scale storms, have often focused on the meteorological parameters such as wind, pressure and vorticity. However, studies using non-meteorological proxies, such as forest damage, describing for storm impacts, have been found to be valuable, as they are independent of meteorological measurements and models. In this study, we present analyses of forest losses caused by large scale windstorms in 1951-2010. We employ primary damage (PD) data from the European forest institute database comprising nearly 300 hundered reports. In addition, we use total growing stock (TGS) of European forests as well as the daily North Atlantic Oscillation (NAO) index to investigate the decadal variability and trends. The NCEP/NCAR reanalysis surface pressure, 850 hPa temperature and 500 hPa geopotential fields were further used to ensure that the PD reports were representative of large scale storms (diameter > 500 km). All of the storms included in the final analysis had caused at least 2 Mm³ PD. Removing the bias caused by and increase in TGS in our analyses, we focused on PD/TGS rather than PD as our primary indicator or damage. Climatic varibility and change were assessed analysing storm intensity as a function of NAO and as a function of time. Our main goal was to assess whether the storm intensity trends are significant relative to the ongoing climate change. Using the validated set of large scale storms, we found that the average decadal PD/TGS had risen from 0.46 % in 1951-1980 to 1.27 % in 1981-2010. Additionally we detected that the decadal storm intensity has increased. Both trends are highly positive and their statistical significance is over 95% (p=0.001). In accordance with earlier studies we found that DJF storms were correlated with the NAO index whereas autumn storms were not. Additionally, our analyses indicated that winter storm activity did not decrease as much in the 2000s, as could be inferred from the NAO index. We thus present our analyses to discussion about the possibility that impact of climate change on the North Atlantic storms hitting Europe has already started during the last two decades.