Projected heat- and cold-related mortality impacts under various climate change scenarios in Switzerland: the role of population development

Abstract

Climate change and progressive ageing of the population is amplifying the heat-related mortality burden in Switzerland. However, limited quantitative evidence exist as to how future trends in heat- and cold-related mortality impacts will develop under various scenarios of warming and population demographics, as well as the contribution of each these two drivers combined. Therefore, we aim to project heat- and cold-related mortality under various climate change scenarios (RCPs) and scenarios of population development defined by Shared Socio-economic Pathways (SSPs), and to disentangle the contribution of each of these two drivers using high-resolution mortality and temperature data in Switzerland.To project future heat- and cold-related mortality impacts under RCP4.5/SSP2 and RCP8.5/SSP5, we estimated the temperature-mortality association using a two-stage time series analysis for each district and age group (<75 and ³75years) between 1990-2010 in Switzerland. Subsequently, we estimated the corresponding future cold- and heat-related mortality impacts for different warming levels (1.5°C, 2.0°C and 3.0°C) for RCP4.5/SSP2 and RCP8.5/SSP5 and disentangled the contribution of population development and change in climate (i.e., temperature).  We estimated that heat-related mortality will increase from 312 (95%CI:116; 510) annual deaths to 1,274 (95%CI:537; 2,284) deaths for RCP4.5/SSP2 under 2.0°C warming. This will further increase up to 1,871 (95%CI: 791; 3,284) for RCP8.5/SSP5 under 3.0°C warming, which is mostly driven by population ageing (53%) rather than temperature (47%). As a result of changes in population development, also cold-related mortality will substantially increase from 4,069 (95%CI:1,898; 6,016) annual deaths to 6,558 (95%CI:3,223; 9,589) annual deaths under 2.0°C of warming and to 5,997 (95%CI: 2,951; 8,759) annual deaths under 3.0°C of warming in RCP8.5/SSP5. In conclusion, both heat- and cold-related mortality will substantially increase under all scenarios of climate change and population development under all degrees of warming in Switzerland. Moreover, population development will reverse the reduction in cold-related mortality despite a warming climate, and further exacerbate heat-related mortality, leading to a substantial net-increase of non-optimal temperature impacts in Switzerland.