Anticipating Hot Summer Nights

Summer heat waves pose health threats to the general population, in particular, vulnerable groups. The skill for seasonal prediction of such heat waves has recently advanced. Yet, whether forecast information on this time scale, a time scale at which individual preparedness could still be improved, might be taken up by the general population, has—so far—not been investigated. Here, we present results from a large-scale online experiment with a general population sample in Germany (N = 4,251) to test how households respond to risk assessments for the number of heat events in their regions for the summer of 2024. Heat events are the number of tropical nights, i.e., with a temperature minimum of at least 20°C, during summer 2024 (June 1^st – August 31^st). As a risk assessment we use the 75percentile of an ensemble with 30 members originating from the operational seasonal forecasts with the German Climate Forecast System (GCFS2.1, Deutscher Wetterdienst, DWD). Participants were exposed in May 2024 to forecast information for the number of heat events in their region of residence, and in addition were provided with the typical summer in the absence of anthropogenic climate change. We present the consequential choices for self-interested and altruistic preventive adaptation measures, as well as for support for mitigation efforts participants demonstrated. Our results identify the impact of ’forward attribution’ to climate change, i.e., information on how the risk assessments would have differed for a world without anthropogenic climate change. We also check whether the perceived reliability of the seasonal prediction spills over to the perceived reliability of long-term climate predictions.