People influence the weather on a weekly basis

Climate change in miniature

Even on short time scales, humans are intervening in climate change: Scientists at the Forschungszentrum Karlsruhe have been able to show that human activities influence various meteorological parameters in Germany on a weekly basis. The average daily temperature on Wednesdays reaches a maximum and drops again for the weekend. © Institute of Meteorology and Climate Research of the Forschungszentrum Karlsruhe
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Now it is official: If you can not be happy about the sunshine on Monday and Tuesday, after the weekend was rainy, you're right. Scientists at the Forschungszentrum Karlsruhe have now been able to prove that humans influence the climate much more directly and more quickly than previously thought.


A study now published in the journal Geophysical Research Letters clearly shows that on Tuesdays the sun shines longer than on other days of the week, on Wednesdays it is on average 0.2 degrees Celsius warmer than Saturdays. It rains the most. According to the authors of the study, which evaluated about 6.3 million readings from 12 stations from the period from 1991 to 2005, a significant weekly trend can be identified. "This phenomenon occurs not only at stations in relatively densely populated regions such as Berlin, Frankfurt or Karlsruhe, but also at remote mountain stations such as on the Zugspitze, " notes Dr. med. Dominique Bäumer, who, together with his colleague Dr. Bernhard Vogel at the Institute for Meteorology and Climate Research of the Research Center and at the University of Karlsruhe.

Fine dust ensures clouds and rain

"As a trigger for this week's trend, we can only imagine aerosols, " said Dr. med. Bernhard Vogel. Aerosols are smallest particles, better known as fine dust. "We've known for a long time that aerosols play a big role in cloud formation and thus influence the weather, " explains Vogel. Through clouding and reflection from sunlight, aerosols can affect temperature, precipitation, and coverage. During the week, aerosol emissions are much higher than at the weekend. Traffic and industry are in full swing from Monday morning and the aerosol concentration is rising.

"We wanted to use the study to find out whether the uneven emission of aerosols - and thus the influence of humans - can be measurably reflected in short periods of time." The study has now proven that humans not only influence the climate over long periods, but also It also initiates short-term processes that have a direct impact on daily weather. display

Saturday is washing day

Saturday is the coolest and rainiest day of the week. Ten percent longer and fifteen percent more rain at the beginning of the weekend. With the rain, a large part of the aerosols released during the week fall to the ground the atmosphere is purified. But why then does not Sunday live up to its name and that it is the sunniest day, requires further investigation of the exact connections. Only at the beginning of the week does the sun shine more. On Mondays it is already much better, but the sunniest day is Tuesday. Then the sun shines on average fifteen minutes or six percent longer than on Saturday. Connections of this kind have already been shown for North America and even for the North Atlantic.

Why the weather lags behind the aerosol production, which is the lowest on Sunday, the researchers can only guess. "It will probably take a while for the aerosols to develop their full effect as condensation nuclei and thus stimulate cloud formation, " says Vogel. How strong the time delay is and which factors play a role is still uncertain. But the researchers want to get to the bottom of these and other questions with computer models.

Although we have not clearly demonstrated a cause-and-effect effect between aerosol emissions and weather, we can not imagine where else the weather might know which day of the week is . It is especially annoying that the effect is more pronounced in summer than in winter.

(Kirsten Achenbach, DFG Research Center Ocean Frontier, 02.03.2007 - DLO)