Changes in Global and Regional Characteristics of Heat Stress Waves in the 21st Century

Abstract

Wet bulb globe temperature (WBGT), a combined measure of temperature and humidity effects on thermal comfort, is used to define heat stress waves (HSWs). While emerging research has raised concerns on future changes in heat stress, for the first time, this study examines spatiotemporal changes in multiple HSW characteristics (intensity, duration, frequency, and cumulative mean intensity) in the 21st century under three emissions scenarios. It is the sustained nature of HSWs that impose more adverse impacts than extreme heat on a single day. HSWs are expected to be more intense, persistent, frequent, and influential due to anthropogenic influence. Models project the largest increases in multiple HSW characteristics will occur over the tropics and subtropics. The exception is maximum intensity, which displays a relative uniform increase over most global land areas. Analysis of regional population exposure to HSWs under different climate and socioeconomic scenarios emphasizes the importance of aggressive mitigation to minimize the potential impacts of HSWs. We further investigate how different regional HSW characteristics are projected to change relative to increasing global mean surface temperature (GMST). Our results confirm the varying rates and different trajectories at which regional HSWs change, independent of forcing pathway, strongly related to GMST. On both globally aggregated and regional scales, the maximum intensity and GMST are highly linearly associated, with an approximately 1:1 increase. However, the other three HSW characteristics are projected to change at a nonlinear rate per degree of GMST increase in general and display large regional variation in the rates of their changes. Plain Language Summary Besides air temperature, air humidity is another important factor in determining the impact of heat waves on humans. High humidity will reduce the efficiency of evaporative cooling and, when combined with high temperature, could pose a serious threat to human health or even life safety. Heat stress indices, taking into account both temperature and humidity effects, are considered to be better indicators of environmental conditions conducive to heat stress on human health. We here employ a widely used heat stress index, wet bulb globe temperature, to define heat waves, namely, heat stress waves (HSWs). Heat waves can be considered through a number of characteristics, and it is their distinctive characteristics that result in the vast array of adverse impacts. This also applies to HSWs. Our results show that more intense, longer-lasting, frequent, and influential HSWs are anticipated during the 21st century, and anthropogenic warming substantially increases the occurrence of HSWs. Except intensity, tropical regions will generally witness the largest increases in multiple HSW characteristics and the number of people that may be exposed to HSWs. Changes in HSW characteristics are confirmed not to depend on whether a particular warming is reached sooner or later; they are strongly related to global mean sur...

Assessment of the Regional and Sectoral Economic Impacts of Heat‐Related Changes in Labor Productivity Under Climate Change in China

“…Both GCM data sets and reanalysis data sets are interpolated to 0.5° × 0.5° grids using bilinear interpolation. The detailed information is described elsewhere (Chen et al., 2020).…”

“…manuscript submitted to Earth's Future third of the world's population is exposed to deadly climate conditions for nearly one month of every year (Mora et al, 2017). Heat stress is occurring more frequently under climate change (Sherwood & Huber, 2010) (Luo & Lau, 2018) (Chen et al, 2020(Chen et al, ), and 2015(Chen et al, -2019 were the five hottest years on record (Watts et al, 2020). Since climate change-related indicators show a trend of accelerating deterioration (Perkins-Kirkpatrick & Lewis, 2020), most researchers use the wet bulb globe temperature (WBGT), which has a wide range of applications in occupational safety and health (Epstein & Moran, 2006) (Lemke & Kjellstrom, 2012), as an indicator of heat stress to estimate future labor productivity by quantifying its relationship with WBGTs (Kjellstrom et al, 2009) (Dunne et al, 2013) (Flouris et al, 2018).…”

“…Heat stress is occurring more frequently under climate change (Chen et al., 2020; Luo & Lau, 2018; Sherwood & Huber, 2010), and 2015–2019 were the five hottest years on record (Watts et al., 2020). Since climate change‐related indicators show a trend of accelerating deterioration (Perkins‐Kirkpatrick & Lewis, 2020), most researchers use the wet bulb globe temperature (WBGT), which has a wide range of applications in occupational safety and health (Epstein & Moran, 2006; Lemke & Kjellstrom, 2012), as an indicator of heat stress to estimate future labor productivity by quantifying its relationship with WBGTs (Dunne et al., 2013; Flouris et al., 2018; Kjellstrom et al., 2009).…”

Tropical deforestation accelerates local warming and loss of safe outdoor working hours

“…Specifically, humid heat exposure, as measured by HI or wet bulb globe temperature (WBGT), is expected to increase as the globe warms, 46,51 which will have implications for productivity of both agricultural workers, crops, 77 and livestock, 78 as well as the intensity of heat waves and associated heat stress in the tropics and subtropics. 79 There is an urgent need to bolster the climate resilience of rural populations in tropical low-and middle-income countries whose populations are often identified as contributing the least to climate change, but are expected to bear a disproportionate burden of its negative effects. 80,81 Activities that drive deforestation, such as the expansion of agriculture or logging, are relatively predictable and can be mitigated by proactive land use planning that takes into account the cooling services provided by trees.…”

On the Controlling Factors for Globally Extreme Humid Heat

“…Extreme humid heat—the combination of high temperatures and specific humidity—is rapidly intensifying globally and poses a threat to societies in multiple climate zones through its impacts on human health, energy demand, and economic productivity (Buzan & Huber, 2020; Chen et al., 2020; Dunne et al., 2013; Li et al., 2020; Mora et al., 2017; Raymond et al., 2020). It is only recently that climate studies have treated moisture as an important dimension for understanding location and timing of impactful regional heat extremes, both presently and for future climate change (Buzan & Huber, 2020; Coffel et al., 2019; Fischer & Knutti, 2013; Mishra et al., 2020).…”