Global and cross-country analysis of exposure of vulnerable populations to heatwaves from 1980 to 2018

Jonathan Chambers

doi:10.1007/s10584-020-02884-2

Abstract

Heatwaves have become more frequent and intense due to anthropogenic global warming and have serious and potentially life-threatening impacts on human health, particularly for people over 65 years old. While a range of studies examine heatwave exposures, few cover the whole globe and very few cover key areas in Africa, South America, and East Asia. By using global gridded climate reanalysis, population, and demographic data, this work analyses trends in change in exposure of vulnerable populations to heatwaves, providing global and per-country aggregate statistics. The difference between the global mean of heatwave indexes and the mean weighted by vulnerable population found that these populations are experiencing up to five times the number of heatwave days relative to the global average. The total exposures, measured in person-days of heatwave, highlight the combined effect of increased heatwaves and aging populations. In China and India, heatwave exposure increased by an average of 508 million person-days per year in the last decade. Mapping of changes per country highlighted significant exposure increases, particularly in the Middle East and in South East Asia. Major disparities were found between the heatwave exposures, country income group, and country health system capacity, thus highlighting the significant inequalities in global warming impacts and response capacities with respect to health across countries. It is therefore of prime importance that health development and response are coordinated with climate change mitigation and adaptation work.

Highlights

Anthropogenic global warming is driving an observed increase in the frequency, intensity, and duration of global heatwaves and warm spells, with these trends projected to continue in the future (IPCC 2013a; Perkins-Kirkpatrick and Gibson 2017; Perkins et al 2012)
This study developed heatwave indexes from global climate reanalysis data and combined these with global population, demographic, and health data covering the period from 1980 to 2018
We demonstrated that there is a clear trend in increasing heatwave days globally, in accordance with climate model predictions for the effects of anthropogenic climate change

Summary

Introduction

Anthropogenic global warming is driving an observed increase in the frequency, intensity, and duration of global heatwaves and warm spells, with these trends projected to continue in the future (IPCC 2013a; Perkins-Kirkpatrick and Gibson 2017; Perkins et al 2012). Heatwaves have been shown to have serious and potentially life-threatening impacts on human health (Anderson and Bell 2009; Basu and Samet 2002; Campbell et al 2018; Hajat and Kosatky 2010; Krau 2013), with specific events noted as public health disasters such as in Chicago during July 1995 and in France during August 2003 (Krau 2013). It has been observed that health effects increase as temperatures rise above certain heatwave thresholds (Lin et al 2009). There is evidence of acclimatisation to local hot climates, all persons are negatively affected by temperatures in the extreme percentiles of their local climatologies (Anderson and Bell 2009), with statistically significant effects on mortality when temperatures surpass the 99th percentile even in locations which display evidence of adaptation to heatwaves (Gasparrini et al 2015a). It has been noted that high night-time (minimum) temperatures in particular have high health impacts because of a lack of night-time relief from excessive heat, which would allow the human body to rest and recover from heat stress (Smith and Levermore 2008; Watts et al 2015)

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