Changing climate both increases and decreases European river floods.

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere1. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe2. Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe3, because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results-arising from the most complete database of European flooding so far-suggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century4,5, suggesting that climate-driven changes are already happening and supporting calls for the consideration of climate change in flood risk management.

Identification of maladaptive behavioural patterns in response to extreme weather events.

Human behaviour has gained recognition as a critical factor in addressing climate change and its impacts. With extreme weather events posing risks to vulnerable communities, understanding cognitive processes driving behaviours becomes essential for effective risk communication. This study focuses on the 2018 "Vaia" storm, which brought unprecedented precipitation and wind velocity to the mountainous regions of North-eastern Italy. Drawing upon the Protection Motivation Theory (PMT) framework, we employ probabilistic models to identify distinct groups with similar behavioural profiles. By administering a web-based survey to 1500 residents affected by the event, we find that threat appraisal is more influential in shaping protective behaviours than coping appraisal. Our findings indicate that by enhancing coping appraisals and discouraging non-protective measures, we can actively mitigate maladaptive responses and promote the adoption of effective adaptation strategies.

The impact of glacier shrinkage on energy production from hydropower-solar complementarity in alpine river basins.

Variable energy sources such as solar and runoff sources are intermittent in time and space, following their driving hydro-meteorological processes. Recent research has shown that in mountainous areas the combination of solar and hydropower has large potential (termed complementarity) to cover the temporal variability of the energy load and, by this mean, to facilitate integration of renewables into the electricity network. Climate change is causing widespread glacier retreat, and much attention is devoted to negative impacts such as diminishing water resources and shifts in runoff seasonality. However, the effects of glacier shrinkage on complementarity between hydropower and solar energy sources have been disregarded so far. This research aims at filling this gap. Data from the Eastern Italian Alps are used for the analysis. The Decision Scaling approach is used to analyze the electric energy system sensitivity and vulnerability to change in precipitation, temperature and glacier coverage. With this method, the electric energy system is first subject to a scenario-independent climate stress test, while projections from Regional Climate Models (RCMs) are then used to infer the likelihood of the future climate states and subsequently changes in complementarity of energy production. Results show that glacier shrinkage and increasing temperatures induced by climate change lead to a marked shift of seasonal hydropower production. As a consequence, the complementarity between hydropower and solar photovoltaic increases in a marked way in the basin with the largest original glacier coverage. Changes in complementarity are less significant in larger basins characterized by less glacier contribution.

Changing climate shifts timing of European floods.

A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.