Making Cities Fit for the Heat
Extreme heat is an increasingly posing challenge for our cities. Researchers at KIT are developing AI-assisted climate models to improve the planning of urban spaces and adapt them to climate change. The goal is to ensure that cities remain livable for everyone.
“Not all kinds of heat are equal,” explains Dr. Ferdinand Briegel from KIT’s Institute of Meteorology and Climate Research – Troposphere Research. The amount of strain caused by high temperatures depends on many factors: air humidity, wind, shadow, type of ground, and development intensity. The shapes of buildings and the materials used to construct them, street courses, green spots, and water surfaces all have an influence on the heat distribution within cities. These aspects contribute to the so-called “thermal index” – a characteristic Briegel’s team calculates with the aid of Artificial Intelligence (AI). Besides local measurement data, the model also uses meteorological information and data about the city structure.
Freiburg as a Role Model
The researchers used their method to investigate the city of Freiburg. The AI model is able to calculate its thermal index hourly – with a resolution of one meter. “We capture every tree and every shadow cast,” says Briegel. The differences between day and night are also considered. Surfaces that heat up heavily during the day can contribute to heat dissipation at night.
Issue 3/2025 of the research magazine lookKIT explores how urban life might evolve in the future.
To the MagazineThe simulations show that even within the same climate zone, great differences exist between urban quarters because of such factors as different vegetation or varying ages of built-up areas. The model also reveals that there are different hotspots during the day and at night. Additionally, it allows forecasts to be made up to the year 2100 and shows the impact of building and landscape development.
Systematic Creation of Green Areas
“A city is like a breathing mosaic”, says Briegel. Trees are important, but not useful everywhere. A dense canopy, for instance, can prevent the evacuation of heat and fine dust if there is no air circulation. The model can also contribute to the targeted planning of schoolyards: Shade, material used for facades, and greening have a considerable impact on the microclimate.
Another advantage of the model is its promptness. While conventional simulations require high-performance computers and several days for their calculations, this model works with a commercial home PC that has a good graphics adapter. Computations that formerly took hours now finish in seconds. Next, the researchers intend to analyze Paris and other cities in Germany – cities with very different structures.
Historical Cities in the Focus
Urban planners at KIT use digital models, too. Professor Markus Neppl and Dr. Peter Zeile from the Institute for Urban and Landscape Design, which is part of the KIT Department of Architecture, compute climate adaptation and climate actions not only for development areas, but also for historical cities.
In Landsberg (Bavaria), for example, they managed to identify suitable spaces for photovoltaics without violating preservation requirements. “Photovoltaics can also be introduced in historically grown areas,” says Neppl. “Sometimes, special and more expensive modules are required that blend with the structures optically.” The team also computes where standard modules can be used without ruining the cityscape.
Encouraging Rather Than Banning
“We recommend incentives instead of bans,” Neppl says. This is a way to also win over private owners for climate action. He states that this applies to solar energy systems in the same way as for heat protection measures. Zeile adds: “Climate adaptation is today being considered in every plan for a new building or for densification.”
However, there is often a gap between knowledge and actual implementation. For the site of the former Karlsruhe slaughterhouse, the team advised against densification. Instead, the researchers suggested greening, sun sails, greening of facades and roofs as well as water misting systems, although the latter were not adopted due to the operating costs.
Long-Term Thinking
Some measures can be implemented quickly, but the reconstruction of entire urban quarters or cities takes time – often decades. “For long-term plans, the new AI models are a major benefit,” says Neppl. They are setting the course today for a climate-resilient future. Whoever wants to do something for the urban climate in their own garden, on their balcony or at their front door can make a significant difference – even with small actions. “A well-groomed tree not only provides shadow but also improves the microclimate in a noticeable way.” recommends Zeile.
Brigitte Stahl-Busse, October 9, 2025
Translated by Fachübersetzungen Hunger/Altmann GbR
