Mortality during heatwaves 2003-2015 in Frankfurt-Main - the 2003 heatwave and its implications

Heatwaves have always occurred, but they are expected to intensify in frequency, duration and intensity due to climate change. Germany (like most European countries) experienced a distinct heatwave in 2003. Afterwards local heat health action plans (HHAP) were implemented in numerous regions (for example in Hesse). This analysis was designed to compare the heat wave of 2003 with the following ones in 2006, 2010 and 2015. We discuss whether measures from the Hessian HHAP were effective in reducing mortality and identify specific characteristics of the 2003 heatwave which did not allow direct comparison. Mortality and temperature data from the city of Frankfurt collected between 2003 and 2015 was used to answer the question of whether the implemented HHAP were effective, or if the mortality in 2003, pre-HHAP implementation, was especially high due to other factors. Excess mortality in 2003 was considerably higher for the overall population than in the heatwaves of the following years (2003: 77.8%, 2006:12%, 2010: 22.7%, 2015: 38.1%). Heatwaves did not result in a significant excess mortality at all in some years, e.g. in 2006. Aside from the mortality rate, the duration of the heatwave (2003: 12 days; 2006: 5 days; 2010: 5 days; 2015: 5 days) was the only differing characteristic, leading to the hypothesis that heatwave duration might be a better indicator of mortality during heatwaves, than other characteristics, alone or combined, hi summary regardmg the effectiveness of the HHAP remains inconclusive since the pre-HHAP heatwave of 2003 differed in certain characteristics (especially the longer duration). Furthermore, the activities representing the HHAP were diverse and were implemented stepwise over some years. The effects on mortality of individual activities cannot be evaluated. Further research should consider differences, e.g. between places (climate zones etc.) and heatwave definitions.