Changes in winds and storms in the context of climate change are much more difficult to record and calculate using climate models than changes in temperature. This is mainly because wind exhibits high variability on small spatial and temporal scales. Furthermore, unlike temperature, wind is not directly influenced by changes in the radiation balance, but arises indirectly from pressure differences that depend on numerous factors.

Pinto et al. (2024) provide a comprehensive overview of the state of research on wind in climate change in their review for the book “Climate Change in Germany”. They summarize various studies and conclude that previous wind trends in Germany are not clear. For the future, there are indications that cyclones over Western Europe could become less frequent overall, but that particularly strong cyclones could occur more frequently. [1]

Subproject ECCES II (C10, "Climate Change Impacts on Storm Surges in the North Sea") confirms this trend for the German Bight [2]. They describe that storm activity is also decreasing overall here, but that particularly extreme storms could occur more frequently or intensely in the future.

Mechanisms affecting storms in the context of climate change

Storms over Europe, during the development of which a great deal of energy is released through cloud formation, bring more precipitation and locally stronger gusts of wind. The subproject “Intensity and structural changes of extreme mid-latitude cyclones in a warming climate” (A6 CyclEx) compared 20 storms with an identical dynamic structure in today’s climate and in a climate that is 3°C warmer. Overall, the comparison shows no systematic change in intensity. In line with precipitation increase, the contribution of energy released by cloud formation increases, but is offset by other processes.Therefore, the changes in wind gusts are not clear. They intensify during some storms, while they weaken during others. Overall, findings suggest that these changes vary greatly from case to case and that wind changes can therefore only be described in general terms to a limited extent.

Extratropical cyclones often exhibit clustering behavior, characterized by multiple cyclones passing over a given location within a short period of time. As a result of ScaHa’s (B3.3, "Statistical modeling of spatio-temporal weather extremes") research, the inter-exceedance times between extratropical cyclones can be described by a fractional Poisson process with seasonal variation, addressing both temporal clustering and seasonality and improving classical models such as the Poisson process substantially. In a similar analysis, the subproject found the inter-exceedance times between heat days to be represented well by a zero-inflated discrete Weibull distribution with seasonality and a decreasing trend, suggesting longer and more frequent heatwaves over Europe.

Severe convective storm (SCS) hazardsare becoming an increasing threat to society and property in a warming world. Using a statistical framework and climate models, CHECC-II (C11, "Convective Hazard Evolution under Climate Change") developed future projections for lightning, hail > 2 cm, hail > 5 cm, and tornadoes > (E/I)F1 for different warming scenarios (+1.5°, +2.0°C, +3.0°C) according to the SSP58.5 scenario. In addition, the models were used to develop an event set spanning 7500 years of stochastically generated hail and tornado swaths across Germany, allowing the project to estimate the risk associated with extreme convective events beyond what has been observed historically.

Impacts

Within FORTEC (C09, "Risks and Uncertainties to Forests and Trees from Extreme Events in a Changing Climate"), statistical models were developed to predict and assess the risk of storm damage to buildings and trees falling onto railway tracks. In addition to the daily maximum wind speed, the duration of the storm and the gust factor influence the risk of both types of damage; the risk of trees falling also increases with precipitation and soil moisture. As a final step, the models are used to estimate future damage risks on the basis of climate model data.

Project ECCES II (C10, "Climate Change Impacts on Storm Surges in the North Sea") uses hydrodynamic tide-surge modeling and sensitivity experiments to evaluate regional sea level rise (SLR) effects on storm surges in the German Bight with a focus on the nonlinear processes and to quantify impacts of offshore wind farm development scenarios on wind, waves and surges. The results show that tide-surge interaction contributes largely to the uncertainties in water level simulations; nonlinear SLR effects are systematic but small (a few centimeters for 1 m SLR), supporting linear superposition for many practical applications, while highlighting that nonlinear interactions introduce process-based adjustments relevant to precise estimates of extremes. Offshore wind farms reduce wind forcing, leading to lower surge and wave heights, with an effect comparable in magnitude to climate-change-driven changes (excluding SLR).

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