Future Heat-Related Mortality in Türkiye: Projections Under CMIP6 Scenarios Towards National Climate Action Targets

Climate change associated with higher temperatures and more frequent/stronger heat waves has been causing adverse health effects and increasing vulnerability in the mega-city of İstanbul. To adapt to climate change and extreme heat, it is crucial to consider the associated health risks. This study aims to estimate current and future mortality risks associated with high summer temperatures in İstanbul. Using data from 2013 to 2017, mortality risks and total attributable mortalities during the summer period were predicted for mid-century (2053–2057) and end-century (2093–2097) under various SSP climate scenarios. Daily maximum temperatures were correlated with daily deaths using a distributed lag non-linear model to estimate relative risks. Future temperatures were projected using recent climate models (CMIP6-GCM), with an average taken from eight models using a multi-model ensemble approach. Statistical downscaling and calibration with observation data were applied, with quantile delta mapping (QDM) providing the most accurate bias-correction. Compared to the reference period, average extreme temperatures in summer months (June-July-August) are expected to remain almost constant (34 °C) until mid-century (over the entire period 2015–2050), while end-of-century extreme temperatures are projected to increase by 1.2 °C (-0.4–3.4 °C) under SSP1-1.9 and 6.6 °C (3.1–11 °C) under SSP5-8.5. Future attributable mortality rates in summer are projected to rise by 15.6% (95% CI: 0.4–37.2%) in 2053-57 and 38.0% (95% CI: 3.7–63.3%) in 2093-97 under SSP5-8.5. Achieving Türkiye’s net zero emission target by 2053 (SSP1-1.9) and implementing adaptive policies could reduce the expected attributable deaths for summer months in İstanbul by 39.7%, from 15,732 mid-century to 9,482 by end-century. By recognising these risks, policymakers can more effectively anticipate and mitigate the impacts of extreme heat on urban populations.