Population ageing determines changes in heat vulnerability to future warming

Chang-Eui Park,Sujong Jeong,Luke J Harrington,Myong-In Lee,Chunmiao Zheng

doi:10.1088/1748-9326/abbd60

Abstract

Population ageing, an increase in the older age group’s portion of the total population, worsens the heat tolerance of a society. However, impacts of ageing on the social exposure to projected unprecedented hot summers (UHSs) are uncertain. We show that a shifting of the population distribution towards older ages amplifies the vulnerability of a country to the increasing frequency of UHSs as a result of warming during 2040–2070, especially in most populated regions such as China, India, and sub-Saharan countries. The warming scenarios from Representative Concentration Pathway (RCP) 8.5 are combined with population scenarios from three Shared Socio-economic Pathways (SSPs) SSP2, SSP3, and SSP5 together to estimate the exposure to UHSs. The ageing-driven increase in the exposure of elderly to UHSs ranges 51–198, 91–261, and 47–156 million in China, India, and sub-Saharan countries, respectively, between population scenarios. In China, with decreasing total population, the exposure to UHSs will be increased by rapid population ageing. In India and sub-Saharan countries, the potential of ageing to raise the exposure to UHSs will be even larger than that of warming. In contrast, in aged societies with slow ageing trend, e.g. United States and Europe, the warming mainly increases the exposure to UHSs. Our results suggest the changing age structure could exacerbate a country’s heat vulnerability despite limiting warming to a certain level in the future.

Highlights

Population ageing is one of the most significant contributors to world population change (Baccini et al 2011, Basu 2009, World Health Organization (WHO) 2015a, Li et al 2016, United Nations 2019a)
We show that a shifting of the population distribution towards older ages amplifies the vulnerability of a country to the increasing frequency of unprecedented hot summers (UHSs) as a result of warming during 2040–2070, especially in most populated regions such as China, India, and sub-Saharan countries
This study aims to quantify the importance of ageing with reference to the increase in the exposure of older persons to unprecedented future heat in six regions with large populations, namely, China, India, sub-Saharan countries with low-incomes (SSA-L), Brazil, United States (US), and the 15 countries that joined the European Union prior to 2004 (EU15) during the mid-21st century

Summary

Introduction

Population ageing is one of the most significant contributors to world population change (Baccini et al 2011, Basu 2009, World Health Organization (WHO) 2015a, Li et al 2016, United Nations 2019a). In Germany, the share of the P65+ reached 21.1% of the total population in 2016, which was larger than that in 1996 by 5.5% (Statistical Office of the European communities 1990). The number of elderly will rapidly increase in highly populated countries with middle- and lowincomes (World Health Organization (WHO) 2011, United Nations 2019b). In China, the population aged 60 years and beyond (P60+) is projected to account for 28% of total population in 2040, which is more than twice the fraction in 2010 (World Health Organization (WHO) 2015b). The percentage of P60+ in India will exceed 10% of the total population in the 2020s, which will further increase by 10%

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Results