Impact of climate and population change on temperature-related mortality burden in Bavaria, Germany
Authors: Rai Masna , Breitner Susanne , Wolf Kathrin , Peters Annette , Schneider Alexandra , Chen Kai 
Published: November 2019

Background. Recent studies on temperature-related mortality burden generally found higher cold-related deaths than heat-related deaths. In the future, it is anticipated that global warming will, on one hand result in larger heat-related mortality but on the other hand lead to less cold-related mortality. Thus, it remains unclear whether the net change in temperature-related mortality burden will increase in the future under climate change.

Objectives. We aimed to quantify the impact of climate change on heat-, cold-, and the total temperature-related (net change) mortality burden taking into account the future demographic changes across five districts in Bavaria, Germany by the end of the 21st century.

Methods. We applied location-specific age-specific exposure-response functions (ERFs) to project the net change in temperature-related mortality burden during the future period 2083–2099 as compared to the baseline period 1990–2006. The projections were under different combinations of five climate change scenarios (assuming a constant climate, Representative Concentration Pathway [RCP] 2.6, RCP4.5, RCP6.0, and RCP8.5) and six population projection scenarios (assuming a constant population, Shared Socio-economic Pathway [SSP] 1, SSP2, SSP3, SSP4, and SSP5). Our projections were under the assumption of a constant vulnerability of the future population. We furthered compared the results with projections using location-specific overall all-age ERFs, i.e. not considering the age-effect and population aging.

Results. The net temperature-related mortality for the total population was found to increase significantly under all scenarios of climate and population change with the highest total increments under SSP5-RCP8.5 by 19.61% (95% empirical CI (eCI): 11.78, 30.91). Under the same scenario for age ≥ 75, the increment was by 30.46% (95% eCI: 18.60, 47.74) and for age <75, the increment was by 0.28% (95% eCI: −2.84, 3.24). Considering the combination SSP2-RCP2.6, the middle-of-the road population and the lowest climate change scenario, the net temperature-related mortality for the total population was found to still increase by 9.33% (95% eCI: 5.94, 12.76). Contrastingly, the mortality projection without consideration of an age-effect and population aging under the same scenario resulted in a decrease of temperature-related deaths by −0.23% (95% eCI −0.64, 0.14), thus showing an underestimation of temperature-related mortality. Furthermore, the results of climate-only effect showed no considerable changes, whereas, the population-only effect showed a high, up to 17.35% (95% eCI: 11.46, 22.70), increment in the net temperature-related deaths.

Conclusion. The elderly population (age ≥ 75), highly vulnerable to both heat and cold, is projected to be about four folds the younger population (age < 75) in the future. Thus, the combined effect of global warming and population aging results in an increase in both the heat- and the cold-related deaths. The population-effect dominates the climate-effect. Mitigation and age-specific adaptation strategies might greatly reduce the temperature-related mortality burden in the future.