How exposure to (urban) heat changes in only three generations. a case study from Bern, Switzerland

More intense and extreme heatwaves are one of the key impacts of advancing climate change in Europe and in Switzerland. While complex climate models are often ineffective at communicating this impact to a broad public, measurements can illustrate it more effectively. In the city of Bern, a unique dataset of urban air temperature measurements for the summer 1973 exists. Using this dataset, a comparison with present day data (2018 to 2024) was conducted to analyze changing exposure to heat from the 1970s to the present day. Based on the latter dataset, air temperatures for future climate scenarios were estimated. The results show that exposure to heat was very low in the city of Bern in summer 1973, at both rural and urban locations. From 2018 to 2024, mainly urban areas are affected by heat, with nationally defined heat warning thresholds being exceeded for several days each summer. In the future, the level of global warming reached will be crucial for the exposure to heat that the citizens are facing. While adaptations measures might still help to reduce impacts in urban areas for a global warming of 1.5 °C or 2 °C, at a + 3 °C warming scenario, high levels of heat exposure are expected in rural areas too, which makes adaptation in this scenario less effective. To make these findings more accessible to a non- scientific audience, we have additionally created a storyline-based comic depicting three Bernese generations and how their exposure to heat is changing over time.