Winter 2023/24 Storms in Western Europe: Intensity, Impacts, and Climate Change Analysis

In the winter half-year of 2023/2024, western Europe was hit by a series of powerful storms that caused significant disruption and increased flood risks. These storms, typical for the autumn and winter months, are characterized by low-pressure systems originating from the North Atlantic Ocean and moving eastward.

Their intensity is influenced by the jet stream, a band of strong westerly winds high in the atmosphere. The 2023/24 season saw a stronger-than-usual jet stream, which likely intensified the storms. The risk of flooding was further compounded by already saturated soils from previous heavy rainfall.

The storm season of 2023/24 marked the ninth year since the Western Europe storm naming group was established. This initiative, initiated by the Met Office and Met Éireann in 2015 and expanded to include the Royal Netherlands Meteorological Institute (KNMI) in 2019, aims to identify and name storms that could have significant impacts. This season’s storms were analyzed using the Storm Severity Index (SSI), which measures wind strength and impact area, to assess their severity.

A collaborative study involving scientists from the UK, Ireland, the Netherlands, Sweden, and Germany focused on the influence of human-induced climate change and the North Atlantic Oscillation (NAO) on storm severity. The study examined storm severity, rainfall, and accumulated precipitation from October 2023 to March 2024. This period was noted for being one of the wettest on record for the UK and Ireland and the region south of 54N.

The 2023/24 storms had severe impacts, including fatalities, flooding, transport disruptions, and power outages. The repeated flooding affected agriculture, and housing, and had broad socioeconomic and psychological consequences, particularly for low-income communities. The cost-of-living crisis further exacerbated these issues, amplifying the effects of the storms.

Analysis revealed that stormy days with the intensity experienced in the 2023/24 season are now occurring approximately every four years, with associated precipitation events occurring every five years.

The seasonal precipitation levels during this period were extreme, expected to happen only once every 20 years. Observations and climate models suggest that human-induced climate change has increased precipitation on stormy days by about 20%, making such severe events approximately ten times more likely.

Future projections indicate continued increases in both average precipitation on stormy days and overall seasonal precipitation in a warmer climate. Despite some studies suggesting a decrease in storminess, the current analysis found that such severe storm seasons as 2023/24 have become less likely due to climate change.

This highlights the need for ongoing research and improved flood risk management strategies, incorporating both traditional engineering and nature-based solutions, to better prepare for and mitigate future impacts.