Climate change unlikely to increase Dunkelflaute events in central Europe - weather service

Wind power output in Germany is not at risk of increasingly being decimated by so-called Dunkelflaute (dark doldrums) events, the country's meteorological service (DWD) has found in an analysis. So-called Dunkelflautes, which usually last several days, occur when weak wind conditions in autumn and winter coincide with minimum solar power output due to reduced daylight time. They usually happen when a high-pressure system in central Europe reduces wind strength in Germany and many neighbouring countries. “Below-average wind energy production is generally to be expected in Germany for the large-scale weather pattern ‘High Central Europe’,” said the DWD.

However, advancing climate change is not expected to increase the risk of the events, which periodically lead to debates about the state of Germany’s energy transition during the winter months. They pose a challenge to Germany’s ambitions to quickly convert its electricity system to 100 percent renewable power sources, as the country still lacks means to bridge a Dunkelflaute without fossil power plants.

The DWD meteorologists’ long-term analyses for the winter half-year “show no significant change” for this weather pattern in central Europe, meaning the expected incidence of low wind power output remains largely unchanged. The mean value for this weather pattern since 1950/51 was roughly 8.2 days per year, with the winter of 2011/12 being an outlier that saw 23 days of a ‘High Central Europe’ pattern.  

Less wind in Germany often means more wind in Scandinavia

The DWD also found that the high-pressure area in central Europe typically coincides with stronger winds in adjacent regions, including Scandinavia and the Balkans. During a longer Dunkelflaute between 2 and 7 November 2024, stronger winds were registered “especially in northern Sweden and in parts of Greece”, the DWD said, adding that this had led to a new monthly record share for wind power output in Sweden of more than 30 percent in the power mix.

This balancing effect of wind strength between central Europe and its fringes confirmed general assumptions on macro weather situations, the meteorologists added. Following a price spike on short-term wholesale power markets during a recent Dunkelflaute event, a member of the Swedish government had complained that demand for electricity imports from Sweden to Germany had greatly increased to compensate for weak turbine output in central Europe.

As Germany’s electricity system continues to increase its reliance on renewable power sources, weather forecasts and long-term macro weather pattern analyses become more important for planning and managing the country’s power grid. A 2018 analysis by the DWD on weather-related risks to renewable power output found that there are on average two cases throughout the year when weather conditions reduce renewable power output to less than ten percent of the nominal output for a duration of more than 48 hours. If viewed in an integrated European network, the incidence dropped to 0.2 cases, the DWD found, stressing the importance of managing renewable power production in a cross-border context.