Adapted heat warning system and recommendations for action

Parts of the team at DWD.
Parts of the team at DWD.

Urban areas are characterized by the heat island effect. Thus, they are exposed to increased thermal stress compared to more rural areas. According to the guidelines of the Sendai Framework for Disaster Risk Reduction 2015-2030, administrations should also be strengthened at the local level to minimize future risks, including exposure to heat. In the project GrüneLunge1.0 we have therefore investigated the heat island effect and the temperature differences within the cities of Karlsruhe and Rheinstetten. Now, with the help of the results of the first project phase, it is necessary to evaluate the heat stress and the risk of people living in urban areas, and to create a tool to make appropriate decisions.


The aim of the subproject is to implement a local specific heat warning system for the city of Karlsruhe under the influence of vegetation and urban structures. The thermal comfort of people is accessible through thermal indices such as felt temperature, which combine meteorological parameters (air temperature, vapor pressure, wind speed, wind direction and global radiation). The thermal indices, which also take into account people's thermo-physiology, provide a way to quantify the impact of people's thermal environments and will serve as a basis for setting thresholds in heat-related mortality. Urban morphology, as well as green infrastructure, alters meteorological parameters and thus human thermal comfort at the small-scale microscale. This is particularly important in the context of climate change and will be incorporated into the small-scale heat warning system. In addition, the risk factors of urban infrastructure, such as hospitals, retirement homes, nursing homes, schools and kindergartens, will be given special consideration.


The specific, small-scale heat warning system should take into account short- and long-term heat reduction measures and issue recommendations for action. If successfully implemented, the proposed method also offers the potential for implementation in other German/European cities with comparable northern latitudes.

Photo: Marcel Gangwisch/DWD