A comprehensive reconstruction of intense precipitation events in the European Alps over a 2,500-year period suggests that periods with a high flooding frequency tend to coincide with cool summer temperatures. The research, published in Scientific Reports this week, could help to improve projections of weather extremes under climate change.

Mean summer temperatures in Central Europe are projected to increase under global climate change, while summer precipitation totals are expected to decrease. Potential enhanced flood occurrence could also increase the risk to settlements, infrastructure, and human lives in the affected regions, including in the Alps. However, the frequency of climate extremes, such as intense precipitation events, is harder to predict.

Lukas Glur and colleagues examined sediment deposits from ten lakes in the Swiss Alps, which they dated using radiocarbon analysis. Lake sediments offer an accurate reflection of past flood activity, as they record individual events as distinct sediment layers. The authors show that floods tend to occur more frequently during cool summers, and they suggest that this wet-cold co-occurrence may be triggered by latitudinal shifts of Atlantic and Mediterranean storm tracks. The palaeoclimate perspective offered by the study could contribute to a better understanding of how global climate change might affect extreme weather events and improve flood-risk assessment in a future warmer climate.