The effect of climate change on heat-related excess mortality in Hungary at different area levels

According to the 5th Assessment Report of IPCC, one of the greatest health impacts of climate change will be the heat-related excess mortality. In Hungary, the National Adaptation Geo-Information System (NAGiS) helps the adaptation process of climate change. Within CRIGiS project, which was initiated to extend the NAGiS, our special subtask was the assessment of heat-related excess mortality at different area levels in the present and for two predicted future periods. This assessment is described in this paper. The Hungarian Central Statistical Office provided the daily mortality data for the period of May 1 - Sep 30, 2005-2014. The observed daily mean temperature data for the same period at small area level (NUTS 4, Nomenclature of territorial units for statistics) were provided by the Hungarian Meteorological Service (HMS). The modeled daily mean temperature data at NUTS 4 level based on the ALADIN-Climate model for three periods, May 1 - Sep 30 of 1991-2020, 2021-2050, and 2071-2100, were also provided by HMS. The heatwave days were defined by the 90th percentile of the frequency distribution of daily mean temperatures at different area levels. The excess mortality was computed by extracting the mean daily mortality of cool days from the number of deaths on heatwave days. As we found a difference between the frequency distributions of observed and modeled present periods, a correction was done assuring that the yearly sums of excess mortality were the same in the observed and modeled present periods. Based on the corrected threshold values the changes in the future could be predicted. During 2005-2014, the range of daily threshold temperature was between 22.3 degrees C and 25.4 degrees C, the mean excess mortality was 15.8% on the heatwave days at NUTS 4 level. At national level, daily mortality was higher by 51 cases on heatwave days than on cool days, which corresponded to an excess of 783 death cases per year in average. According to the climate model, the number and intensity of heatwave days will increase in relation to the present situation. Assuming the same population and level of sensitivity, for 20212050 a 2.6-fold, for 2071-2100 a 7.4-fold increase of excess deaths is predicted causing 2030 and 5800 cases per year, respectively. The prediction of excess mortality at different area levels in the NAGiS database will help stakeholders to prepare adaptation measures to climate change.