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

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.

Borderless Heat Hazards With Bordered Impacts

“…In addition, this study presents evidence that heat stress area has grown since the millennium in the month of August (Figure 2), which is consistent with trends seen in temperature and extreme heat by other studies (Chambers, 2020;Perkins-Kirkpatrick & Gibson, 2017;Vogel et al, 2019;Watts et al, 2018). This provides evidence for the need of a global heat hazard alert system, as heat is not simply impacting one area at a time but many regions simultaneously, even when only considering August as we present here.…”

“…Further, number of exposure hours to heat stress above 26°C is additionally calculated for the months (Nazarian & Lee, 2021). We focus on the Northern Hemisphere, the region with the largest area of land mass and the largest proportion of the global population (Chambers, 2020) and August was chosen because it historically has experienced notable heatwaves in both the Northern Hemisphere during the summer and the tropics where heat extremes do occur throughout the year (Perkins-Kirkpatrick & Gibson, 2017;Russo et al, 2016).…”

“…As exposure to heatwaves is known to be greater in more populated areas (Chambers, 2020;Watts et al, 2017), the gridded data is first masked to land area, excluding Antarctica, and then also masked to populated land area using grid cells with a population count of over 0 from the Land Scan data set for 2000-2019 provided by the Oak Ridge National Laboratory (Dobson et al, 2000;Vijayaraj et al, 2007), with 2020 being masked to 2019 population count. All grid cells are then summed, allowing for proportions to be calculated.…”

“…In addition, during a heatwave the population exposed to the risk of heat stress is increasing and as such populations are experiencing a rise in baseline levels of mortality and morbidity more often during August. Moreover, with an increase in nations with an aging population this risk is greater, as those over 65 are especially vulnerable to heat illnesses and mortality (Arbuthnott & Hajat, 2017;Chambers, 2020;Kovats & Hajat, 2008;WMO & WHO, 2015). We also show how regions with the highest heat stress levels also have the highest exposure time which is an important element when considering heat morbidity and indicates less time to recover from heat exposure (Chambers, 2020;WMO & WHO, 2015).…”

Heat Perception and Coping Strategies: A Structured Interview-Based Study of Elderly People in Cologne, Germany

“…Vulnerable populations experienced additional exposures to 475 million heatwave events, respectively 2.9 billion additional days of heatwaves globally in 2019 [ 8 ]. Heatwaves enhanced impacts to public health, especially for vulnerable groups like elderly people, are of additional significance, as the world’s population is aging rapidly [ 9 , 10 ]. Elderly people are the most vulnerable group because ageing brings about physiological changes that affect people’s thermal sensitivity and thermoregulation; moreover, there is a progressive increase of multimorbidity with increasing age [ 11 ].…”