An urban climate analysis by the company Geo-Net Umweltconsulting from Hanover, commissioned by the city of Bonn, does not bode well for the future. If mankind does not radically reduce emissions of climate gases to zero and additionally remove greenhouse gases from the atmosphere, the year 2020 will almost become the average, the study authors judge. For this purpose, they converted the RCP 8.5 climate projection from the World Climate Report of 2014, which most likely describes a continuation of emissions, to Bonn conditions. In this case, a long-term average annual temperature of 12.3 degrees is to be expected in 2100.

Above all, however, the extremes will increase. In the relatively cool year 2021, there were already 26 summer days. The scientists expect 34 additional summer days above 25 degrees, 16 of them even above 30 degrees. I In addition, there will be eight additional tropical nights in 2100, which will not cool down below 20 degrees and will deprive many people of sleep. Since the calculation quadrants also include cool forest areas, the number of tropical nights in residential areas could actually also increase by 24 to 40 per year. The exception thus becomes the rule in summer.

Residents from the Rhine and Münster quarters in the city centre, from the Ellerviertel and around the goods station, from Beueler Osten or from Godesberg Nord and Godesberg Zentrum can already report what such circumstances feel like. They live on the 13 percent of the settlement area that, according to the small-scale data of the urban climate analysis, already have an unfavourable or very unfavourable bioclimate during the day. Twelve percent of the settlement area is affected at night. "The supply of cold air to the inner city at night is no longer given," the authors warn in principle. Further densification in these areas should be avoided. Since the wooded areas are not within walking distance for many, smaller parks should be created in a decentralised manner.

"The importance of a consistent heat adaptation of the city becomes obvious against this background," writes the city administration in this context in a current communication to the council. Nevertheless, concrete measures remain isolated cases, they admit, following a survey of the specialist departments. Activities for children and young people were moved from the open air to cooler indoor rooms, and fewer sports were offered in exchange for drinks and fruit. Water dispensers have been set up in the "Haus der Bonner Altenhilfe" and the outdoor facilities of the senior citizens' meeting places have been shaded.

A concrete heat action plan for the protection of vulnerable population groups, as suggested by the federal and state governments in 2017 with clear recommendations for action and demanded by the council majority of the Greens, SPD, Left Party and Volt in March, has been rejected by the administration for the time being. This could only be achieved with external expertise and an additional position (75 per cent) in 2024 at the earliest. In addition to the personnel costs, the administration expects costs of 100,000 euros, for which there are currently no funds from the state or federal government. They are in contact with municipalities such as Cologne and Mannheim, which already have such plans. But apparently the administration does not see itself in a position to independently transfer the measures collected there to Bonn conditions.

Clear demand for greening

Now that the urban climate analysis with clear demands, especially for the greening of dense inner city areas, has been on the table since 2019, the city administration retreats to the position vis-à-vis the council that there is a lack of "systematic recording and analysis" of the "adaptation activities" before further measures are taken. That is why they have now applied to the Federal Ministry for the Environment for funding for a "sustainable adaptation concept". An adaptation manager is to begin this two-year work in October. It is not yet known whether the application is eligible for funding.

The costs are expected to be 228,686 euros, with a funding rate of 90 per cent. The public is also to be involved. In June last year, the administration already started the research project "mutabor" as a "municipal lighthouse project", also with funds from the Federal Ministry for the Environment. This is a "micro-scale investigation and activation of the technical and planning adaptation capacity of the city of Bonn to reduce heat stress". Without prejudging the results, the few concrete steps already indicate that the adaptation capacity of the city administration may have narrow limits.

Original text: Martin Wein

Translation: Mareike Graepel