Urban heat vulnerability in a warming climate in Denmark: Projected temperature-related mortality for Copenhagen and the remaining areas

Objective We estimated future cold- and heat-related mortality for Copenhagen and remaining areas in Denmark under different warming scenarios. Methods We used nationwide historical and projected data on temperature, mortality, and population size. For 2000–2019, daily deaths were modelled using a Poisson regression of mortality rates as a function of daily mean temperature using distributed lag non-linear models, accounting for seasonality, weekday, and lags (up to 28 days). Future temperature-related mortality was estimated by applying historical associations to projected temperatures and population under RCP2.6, RCP4.5, and RCP8.5. Analyses were conducted separately for Copenhagen and remaining areas in Denmark. Results Copenhagen had a higher minimum mortality temperature (16.4 °C) than the remaining areas (15.0 °C). Mortality rates increased at higher and lower temperatures and rose more steeply in Copenhagen (±5 °C 8.4%/3.0%) than elsewhere (3.9%/1.0%). By 2099 (RCP8.5), excess heat-related mortality would increase by 0.62% (95% eCI 0.10; 1.34) in Copenhagen and 0.35% (0.08; 0.74) in the remaining areas, whereas excess cold-related mortality will decrease. Conclusion Temperature-mortality relationships differed between Copenhagen and the rest of Denmark, with Copenhagen exhibiting a higher minimum mortality temperature and stronger heat-related risks. As warming progresses, Copenhagen may experience greater relative impacts, underscoring the need for city-specific adaptation strategies.