Projections of windstorms damages under changing climate and demography for Norway

Windstorms cause severe damages and are the dominant natural hazard responsible for insurance payouts in Norway. Using future wind speeds from twenty bias corrected regional climate model simulations from EURO-CORDEX and four damage functions, fitted on municipality level to observed insurance losses, we estimate storm related losses to increase in all Norwegian counties due to climate change. At national level, there is an increase in storm losses in the far future, but some counties and municipalities can still exhibit a decrease in losses. Under a changing climate, despite a decrease in the 98th percentile of the wind speed, the most extreme winds increase, and this drives an increase in the windstorm damages. We also show that the wind load design values may need to be re-evaluated to take into account the changing wind speeds. In addition to climate change, the impact of future exposure changes in the form of population changes using municipality-level population projections is shown to be important for determining the level of future windstorm damage risk. Overall, the loss projections show a large spread, highlighting their sensitivity to the choice of the storm-damage function and to the choice of the simulation.