As of: December 30, 2021 11:00 a.m.
The flood in Rhineland-Palatinate and North Rhine-Westphalia was probably the most defining weather event of the year. According to the German Weather Service, 2021 was sunny and warm overall – and so it fits in with the trend.
The year 2021 ends with record-breaking high temperatures – the 11th in a row to be too warm. The effects are extreme in some places. Physically it’s pretty easy, says Tim Staeger, meteorologist at ARD weather competence center in Frankfurt: “The temperature of an air mass determines how much water fits in.” The warmer, the more water it can bind. “Due to climate change, we are getting warmer air. When a heavy rain event takes place, it is more intense than it used to be.”
This summer there was heavy rainfall and deadly floods in North Rhine-Westphalia and Rhineland-Palatinate. Studies have shown that the likelihood of such weather conditions has increased by 20 percent, says Staeger. In 2021, the average temperature of 9.1 degrees was only about one degree above the reference value, the so-called long-term mean – assessed between 1961 and 1990. The past three years were on average more than two degrees too warm.
But meteorologist Staeger explains: Climate change takes place over many years. A new record cannot be set every year. There are of course fluctuations. This year La Nina pushes global temperatures – a cold water event in the Pacific. But that doesn’t break the trend. This is supported by a survey by Munich Reinsurance. According to this, there were 249 natural disasters with major losses worldwide in 1980. In 2020 there were 980. In particular, increasing heat and heavy rain are causing urban planners in Germany to rethink.
Sponge City is supposed to prevent floods
The trend is towards the sponge city: precipitation should be absorbed where it falls and the city should soak up like a sponge. The aim is to prevent overflowing sewers and flooding. This conversion can already be seen in Offenbach. Cherry trees grow on the roofs of the old harbor. Plants, soil and trees store up to 80 percent of heavy precipitation. A pleasant side effect: In summer, evaporating moisture cools the ambient temperature of green areas by up to five degrees, says Mayor Sabine Groß.
Offenbach is also relying on other measures: The rainwater from the roof of the new police headquarters is stored before it runs into a renatured stream. And: Citizens who unseal garage entrances, for example, are subsidized by the city with up to 50 euros per square meter. “More heat, more storms, more heavy rain. We have to react to that,” says the mayor.
Lots of sun, but also lots of rain
In 2021, like last year, the warmest place in Germany was Cologne – with an average temperature of around 11.4 degrees. According to the German Weather Service (DWD), there were most hours of sunshine in the Allgäu. With more than 2040 hours of sunshine, Leutkirch is currently just ahead of Kaufbeuren. This year there was an average of around 1650 hours of sunshine across Germany. The long-term mean is 1544 hours.
There were also slightly above average values in the rain. An average of 789 liters fall per square meter per year. There were around 805 in 2021. By way of comparison: in the previous year, only 710 liters fell. The forests in particular have suffered badly from the last few years that were too dry.
At least on the surface, that has now improved, says Sarah Liebelt, a forester in Nidda in Hesse. New plants would have got enough rain. “When you reach into the ground, you notice that it is much more humid than in previous years. But that is far from being enough to properly regenerate the forest.” As in many other places in Germany, she is currently converting her forest. “The days of the spruce are over. We are now relying on tree species such as oak and non-native species because they can cope better with drought stress.”
The weather summary for 2021 by Tobias Fuchs, Director Climate and Environment of the German Meteorological Service: “We are experiencing the consequences of climate change live. Extreme weather conditions can affect any of us. Those who protect the climate protect themselves.”