Exceedance of heat index thresholds for 15 regions under a warming climate using the wet‐bulb globe temperature

Abstract

Thermal comfort is quantified in 15 regions using the wet-bulb globe temperature (WBGT), examining past and future rates of thresholds exceedance corresponding to moderate, high, and extreme heat (28, 32, and 35°C, respectively). As recent changes to thermal comfort appear to be dominated by temperature and humidity, a WBGT approximation based only on these is used. A new homogenised dataset from 1973 to 2003 is developed which provides WBGT daily means, daily maximums averaged over 5-day periods, and the highest extreme for each 5-day period; recent trends are positive for all regions except northeast USA and northeast Australia. A simple model for predicting summertime threshold exceedance rates, with a fixed distribution of anomalies about the seasonal mean, is found to adequately predict changes for the above quantities given seasonal mean values. This model is used to predict the impact of regional 1-5°C temperature increases on WBGT exceedance rates with no change in relative humidity. Results show that heat events may worsen as much, or more, in humid tropical and mid-latitude regions even if they warm less than the global average, due to greater absolute humidity increases. A further 2°C warming from the present is sufficient to push peak WBGT above 35°C, an extreme heat event, in all regions except the UK.An ensemble of HadCM3 climate model simulations is used to investigate likely regional changes in mean summertime temperature, relative humidity and WBGT under an A1B scenario for the 2020s and 2050s. Unsurprisingly, simulated regional changes often depart significantly from the global average, and the impact of regional changes in relative humidity is not always negligible. Increases in WBGT are nonetheless expected in all regions, and are more predictable than increases in temperature at least in mid-latitude regions owing to the compensating effects of humidity. 

Detection of anthropogenic influence on a summertime heat stress index

“…Sherwood and Huber (2010) proposed that heat stress imposes an upper bound on how much global warming humans can adapt to, since with large global warming, T w in some regions can approach levels (35°C) that should induce hyperthermia in humans. Willett and Sherwood (2012), in a study of past and future-projected WBGT trends in 15 regions, found positive historical trends in almost all regions studied. Their statistical model suggested that, assuming a uniform 2°C warming above present levels, a 35°C WBGT threshold would be exceeded during at least some extreme events in almost all 15 regions.…”

Effects of Heat Stress on Working Populations when Facing Climate Change

“…The continuous rise of absolute humidity in the lower troposphere has also been reported in many regions which add substantial implications for human thermal comfort and heat-related mortality and morbidity. In particular, this may add substantial risk in already humid countries, where a small increase in temperature can have profound consequences on heat stress 9) .…”

Analytical study of land surface temperature with NDVI and NDBI using Landsat 8 OLI and TIRS data in Florence and Naples city, Italy

“…temperature humidity index, physiological equivalent temperature, wet-bulb globe temperature and urban thermal field variance index (UTFVI). (Kakon, Nobuo, Kojima, & Yoko, 2010;Matzarakis, Mayer, & Iziomon, 1999;Willett & Sherwood, 2012;Zhang, 2006). Among these indices, UTFVI is the most widely used index for the ecological evaluation of urban environment due to its direct relation to LST (Alfraihat, Mulugeta, & Gala, 2016;Li et al, 2013;Liu & Zhang, 2011;Mackey, Lee, & Smith, 2012;Nichol, 2005).…”