Probabilities of adverse weather affecting transport in Europe: Climatology and scenarios up to the 2050s

Adverse and extreme weather events, such as heavy rain, heavy snowfall, strong winds, extreme heat and cold, drought and reduced visibility, can have a negative impact on the transport sector, causing injuries and damages as well as other economic losses. Frequency and intensity of weather and climate extremes are likely to continue to change in the future due to the projected climate change; consequences of changes will be both negative and positive for transportation. The EWENT project (Extreme Weather impacts on European Networks of Transport) funded by the European Commission under the 7th Framework Programme (Transport, Horizontal Activities) has the objective of assessing extreme weather impacts on the European transport system. This report frames the findings of Work Package 2 (WP 2) of the EWENT project. The study provides the first comprehensive climatology of the adverse and extreme weather events affecting the European transport system by estimating the frequency (or probability) of phenomena for the present climate (1971-2000) and an overview of projected changes in some of these adverse and extreme phenomena in the future climate until 2070. The following phenomena are analyzed: wind, snow, blizzards, heavy precipitation, cold spells and heat waves. In addition, visibility conditions determined by fog and dust events, small-scale phenomena affecting transport systems, such as thunderstorms, lightning, large hail and tornadoes, and events that damaged the transport system infrastructure were considered. Frequency and probability analysis of past and present extremes were performed using observational and reanalysis data. Future changes in the probability of severe events were assessed based on six high-resolution regional climate model (RCM) simulations produced in the ENSEMBLES project. There are large differences in probabilities and intensity of extremes affecting transport systems across Europe. Northern Europe and the Alpine region are impacted most by winter extremes, such as snowfall, cold spells and winter storms, while the probability of extreme heatwaves is highest in Southern Europe. Extreme winds and blizzards are most common over the Atlantic and along its shores. Although heavy rainfall may impact the whole continent on a yearly basis, the very extreme rainfall events (over 100 mm/24 h) are relative sparse. Visibility conditions indicate a pan-European improvement over the decades studied; severe fog conditions becoming almost non-existent at some of the main European airports. The multi-model mean climate projections indicate robust changes in temperature extremes, but are less coherent with regard to extremes in recipitation and wind. Both cold extremes and snow events are likely to become rarer, especially in the north where the extreme cold might shorten by 30-40 days/year by the 2050s. On the other hand, heavy snowfalls (>10 cm/day) are not expected to decrease, instead models project a 1-5 days/year increase over Scandinavia. Extreme heat is likely to intensify over the entire continent, being more accentuated in the south (by 30-40 days/year). The analysis of the Baltic Sea ice cover indicates a decrease in the average maximum fast ice thickness of 30-40 cm by 2060. To facilitate the assessment of impacts and consequences of extreme phenomena at the continental level a regionalization of the European extreme phenomena is provided.