Recent Increases in Exposure to Extreme Humid‐Heat Events Disproportionately Affect Populated Regions

Rogers, Cassandra Denise Wilks; Ting, Mingfang; Li, Cuihua; Kornhuber, Kai; Coffel, Ethan; Horton, Radley M.; Raymond, Colin; Singh, Deepti

doi:10.1029/2021gl094183

Cited by 56 publications

(54 citation statements)

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“…Our findings of warming extreme TW values in many of the AR6 regions extend previous results indicating increases in humid heat extremes across the world (Raymond et al, 2020;Rogers et al, 2021) and in parts of Asia, Europe, and North America (C. Li, et al, 2017;Freychet et al, 2020;Mishra et al, 2020;X.-X. Li, 2020).…”

Section: Discussionsupporting

confidence: 88%

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Concentrated and Intensifying Humid Heat Extremes in the IPCC AR6 Regions

Speizer

Raymond

Ivanovich

et al. 2022

Geophysical Research Letters

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Extreme heat can have substantial consequences for human health, especially when paired with humidity Di Napoli et al., 2019;Foster et al., 2021). The majority of heat dissipation necessary for human thermoregulation occurs through evaporative cooling via sweating (Gagnon & Crandall, 2018), rendering extreme humid heat more physiologically stressful than extreme temperature alone (Vanos & Grundstein, 2020). Humid heat extremes are rapidly increasing in frequency (Raymond et al., 2020;Rogers et al., 2021), and are projected to continue to intensify in the warming climate (Coffel et al., 2018), significantly increasing exposure to dangerous levels of humid heat.Various indices are used to quantify the combined impact of temperature and humidity. Wet-bulb temperature (TW) is a particularly useful metric, as it establishes a maximum tolerable intensity of humid heat at about 35°C (Sherwood & Huber, 2010). This survivability limit applies to healthy individuals under optimal external conditions (e.g., in full shade, with access to unlimited drinking water) (Raymond et al., 2020;Sherwood & Huber, 2010). Thus, substantial health effects-including mortality-occur at far lower TW values Raymond et al., 2020;Vecellio et al., 2022). Even less extreme magnitudes of humid heat can cause a variety of societal impacts, such as decreased economic productivity associated with limitations on outdoor labor or increased energy demand due to the need for artificial cooling (e.g.

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Section: Discussionsupporting

confidence: 88%

“…Extending those analyses, we use ERA5 reanalysis data to calculate trends in the intensity of extreme TW values for the land regions in the IPCC AR6 report (Iturbide et al, 2020). These regional-level results complement prior global-scale analyses and more process-oriented work (e.g., Freychet et al, 2020;Mishra et al, 2020;Rogers et al, 2021).…”

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confidence: 90%

Concentrated and Intensifying Humid Heat Extremes in the IPCC AR6 Regions

Speizer

Raymond

Ivanovich

et al. 2022

Geophysical Research Letters

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“…This highlights that the threshold for deadly heat used here is rather extreme, and much lower thresholds are already considered as dangerous. On a daily timescales, TW has rarely exceeded 31 • C in the historical records [14], although some places have experienced hourly peaks above this value [15,16]. Previous studies have also shown that places such as South and East Asia could reach deadly TW conditions in the future under a 'business as usual' greenhouse gas emissions scenario [17].…”

Section: Introductionmentioning

confidence: 99%

Robust increase in population exposure to heat stress with increasing global warming

Freychet

Hegerl

Lord

et al. 2022

Environ. Res. Lett.

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Extreme heat, particularly if combined with humidity, poses a severe risk to human health. To estimate future global risk of extreme heat with humidity on health, we calculate indicators of heat stress that have been commonly used; the Heat Index, the Wet-Bulb Globe Temperature and the Wet-Bulb Temperature, from the latest Climate Model Intercomparison Project (CMIP6) projections. We analyze how and where different levels of heat stress hazards will change, from severe to deadly, and how results are sensitive to the choice of the index used. We evaluate this risk at country-level and use population and GDP growth scenario to estimate the vulnerability of each nation. Consistent with previous studies, we find that South and East Asia, and the Middle-East, are highly exposed to heat stress hazards, and that this exposure increases by 20\% to 60\% with global mean temperature change from 1.5 to 3 degrees Celsius. However, we also find substantial increases in heat health risk for some vulnerable countries with less adaptive capacity, such as West Africa, and Central and South America. For these regions, about 20 to more than 50\% of the population could be exposed to severe heat stress each year on average, independent of the index used. For global warming of 3 degrees, European countries and the USA will also be exposed several times per year to conditions with daily mean heat stress level equal to the maximum heat stress of the 2003 heat wave.

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“…Extreme events are of special importance in the study of heat stress because of their severe impacts. For example, some studies attempt to identify extremely rare, short‐term heat stress events in the past 30 years (Raymond et al., 2020; Rogers et al., 2021) and going into the future (Casanueva et al., 2020; Chen et al., 2020; Coffel et al., 2018; Im et al., 2017; Li et al., 2017; Pal & Eltahir, 2016). In order to quantify sWBGT/ESI biases in measuring extreme heat stress, we fit a generalized extreme value (GEV) model to the time series of annual maximum WBGT, sWBGT, and ESI (calculated from hourly frequency) during 1990–2019 using ERA5 reanalysis data.…”

Section: Methodsmentioning

confidence: 99%

Explicit Calculations of Wet‐Bulb Globe Temperature Compared With Approximations and Why It Matters for Labor Productivity

Kong

Huber

2022

Earth's Future

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Wet‐bulb globe temperature (WBGT) is a widely applied heat stress index. However, most applications of WBGT within the heat stress impact literature that do not use WBGT at all, but use one of the ad hoc approximations, typically the simplified WBGT (sWBGT) or the environmental stress index (ESI). Surprisingly, little is known about how well these approximations work for the global climate and climate change settings that they are being applied to. Here, we assess the bias distribution as a function of temperature, humidity, wind speed, and radiative conditions of both sWBGT and ESI relative to a well‐validated, explicit physical model for WBGT developed by Liljegren, within an idealized context and the more realistic setting of ERA5 reanalysis data. sWBGT greatly overestimates heat stress in hot‐humid areas. ESI has much smaller biases in the range of standard climatological conditions. Over subtropical dry regions, both metrics can substantially underestimate extreme heat. We show systematic overestimation of labor loss by sWBGT over much of the world today. We recommend discontinuing the use of sWBGT. ESI may be acceptable for assessing average heat stress or integrated impact over a long period like a year, but less suitable for health applications, extreme heat stress analysis, or as an operational index for heat warning, heatwave forecasting, or guiding activity modification at the workplace. Nevertheless, Liljegren's approach should be preferred over these ad hoc approximations and we provide a fast Python implementation to encourage its widespread use.

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Recent Increases in Exposure to Extreme Humid‐Heat Events Disproportionately Affect Populated Regions

Abstract: Extreme heat can have devastating impacts on built and natural environments including crop losses, wildfire risk, infrastructure damage, and wildlife mortality (e.g.,

Cited by 56 publications

References 60 publications

Concentrated and Intensifying Humid Heat Extremes in the IPCC AR6 Regions

Concentrated and Intensifying Humid Heat Extremes in the IPCC AR6 Regions

Robust increase in population exposure to heat stress with increasing global warming

Explicit Calculations of Wet‐Bulb Globe Temperature Compared With Approximations and Why It Matters for Labor Productivity

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