“The Climate in Germany Has Already Shifted into a New State”

How can the atlas specifically support policy decisions?

The atlas highlights where climate extremes are changing most dramatically and where regional hotspots are emerging. Local governments, authorities, and policymakers can use this information to prepare more effectively for the consequences of climate change. This applies, for example, to water management, agriculture, and forestry.

If regions experience heat and drought more frequently in the future, this can be taken into account, for example, when selecting climate-resilient tree species or planning long-term adaptation measures. The atlas is designed to help identify developments early on and better assess risks. That is precisely why it was important to us not only to present these developments at the national level but also to make them visible for each federal state (Bundesland). Furthermore, people are particularly interested in climate data when they relate to their own living environment.

We observed this in the initial feedback on the atlas as well. Many people first looked up the year they were born and used the maps to track how conditions have changed since then. This makes the atlas more personal and the changes more tangible. And for policymakers, who must organize regional adaptation measures, the atlas is particularly important.
 

Which trends are particularly evident?

We see the most pronounced changes in temperature and the associated extreme events. Heat waves are occurring more frequently, and the number of tropical nights is also increasing. We define a tropical night as one in which the temperature does not drop below 20 degrees Celsius. This puts a strain on the body because it can no longer recover adequately. Large cities such as Berlin, Frankfurt, Cologne, Hamburg, and Munich are particularly affected. There, impervious surfaces and additional waste heat cause temperatures to remain high for long periods even at night. We expect the sharpest increase in tropical nights in metropolitan areas and along the Upper Rhine Graben.

At the same time, we are observing a significant decline in snow cover. In some regions, significantly less snow falls now than it did just a few decades ago. Overall, Germany has warmed by about 1.9 degrees Celsius since the late 19th century. This trend is particularly pronounced in Saarland.

I am also concerned about developments in eastern Germany. There, dry conditions and drought are increasing particularly rapidly. Even periods of rainfall are often insufficient to replenish depleted soil moisture. Rising temperatures cause moisture to evaporate more quickly, leading to increasingly dry soils.

From a scientific perspective, at what point do individual extreme events become a long-term trend?

The longer the available data series, the better we can identify and statistically evaluate changes. Germany is in a very good position in this regard because we have access to measurement data dating back to the late 19th century.

The analyses for the atlas clearly demonstrate that we are no longer dealing merely with isolated extreme events. We are seeing long-term changes, particularly in temperature extremes. The data suggest that the climate in Germany has already shifted into a new state.

What do you hope people and policymakers will take away from the atlas?

Above all, we wanted the atlas to show just how much the climate in Germany has already changed. Many people react very strongly to the maps. For some, it was even a real visual shock because they were seeing the changes so clearly for the first time.

I hope the atlas helps people better understand these developments. Maps and graphics often make it easier to grasp what lies behind abstract numbers. People can see with their own eyes how temperatures, heat waves, or drought have changed over the decades and more easily recognize how important decisive action is, including in their own communities.

Of course, a book alone will not convince anyone. But if the atlas encourages people to think about these changes and grapple with the consequences of climate change, then we have already achieved a great deal. Our goal was to create a tool that offers guidance and provides a sound foundation for discussions and decisions.

A Compendium of Knowledge on Climate Change – New Atlas of Climate Extremes