Fig. 2: Model validation using chamber experimental data.
From: Widespread outdoor exposure to uncompensable heat stress with warming
The solid points and triangles represent two sets of experiments from the PSU-HEAT project25: MinAct (mean M = 83 W m−2) and LightAmb (mean M = 133 W m−2), respectively. Each experiment includes six trials with either (1) constant Ta and progressively increasing vapor pressure (ea) or (2) constant ea and increasing Ta until the core temperature (Tc) inflection point was observed. These twelve combinations of critical Ta and ea and two levels of metabolic heat (83 and 133 W m−2) are used as inputs to our energy balance model ((Eqs. (1)–(8), model parameters are summarized in Supplementary Table 1), which accurately predicts G around zero for all experiments. The solid lines denote the G = 0 isopleths, indicating the Tc inflection point and the uncompensable heat stress threshold from our model for each level of M in the MinAct and LightAmb experiments. Each point or triangle symbol represents the mean of multiple human subjects, and the error bar represents the standard deviation (vertical bars for fixed Ta trials, horizontal bars for fixed ea trials). Dashed contours are the isopleths of wet-bulb temperature. See Supplementary Fig. 9 for relative humidity (RH) on the Y-axis. More details are provided in the “Methods” subsection “Model validation and cross-comparison”.
