Multidecadal forcing of European windstorm losses in CMIP6-DAMIP models

Abstract

Large variations of European storm activity at decadal and longer timescales have been found to be driven by major tropical volcanic eruptions, internal climate variability and anthropogenic aerosols (AA). The insurance industry have the ability to align with these slow fluctuations in windstorm risk, yet have not done so, due to uncertainty in how the climate diagnostics used by researchers relate to insured losses. A key aim of this study was to link past research findings to insurance applications by measuring the impacts of AA on European property damage. This was done by extracting the winds from a set of climate model experiments on AA forcing and converting them into European storm losses using an established technique. The multimodel mean result indicates AA boosted insured windstorm losses by 45% in the late 20th century relative to preindustrial times, though model changes range from zero to a doubling of losses and suggest large uncertainty in the size of the strengthening. Further analysis of individual model simulations suggested both AA and internal climate variability explain about half of the amplitude of the last peak, implying a significant role for volcanic eruptions. Looking ahead, we cannot be sure of the timing of the next peak since it may require at least one major volcanic eruption, but climate models provide encouraging signs that recent cuts in AA emissions from North America and Europe will act to reduce its severity.