Year: 2024
Type: article
Abstract: The heat index (HI), based on Steadman’s model of thermoregulation, estimates heat stress on the human body from ambient temperature and humidity. It has been used widely both in applications, such as the issuance of heat advisories by the National Weather Service (NWS) and for research on possible changes in the future due to climate change. However, temperature/humidity combinations that exceed the applicable range of the model are becoming more common due to climate warming. Recent work by Lu and Romps has produced an extended heat index (EHI), which is valid for values outside the range of the original HI. For these values, the HI can underestimate the EHI by a considerable amount. This work utilizes observed data from 15 U.S. weather stations along with bias-adjusted output from a climate model to explore the spatial and temporal aspects of the disparity between the HI and the EHI from the recent past out to the end of the twenty-first century. The underestimate of human heat stress by the HI is found to be the largest for the most extreme cases (5°–10°C), which are also the most impactful. Conditions warranting NWS excessive heat warnings are found to increase dramatically from less than 5% of days historically at most stations to more than 90% in the future at some stations. Although, by design, the scope of this work is limited, it demonstrates the need for the adoption of the EHI for both applications and research. Significance Statement An index based on temperature and humidity was developed over 40 years ago to estimate human heat stress. It has been used to issue heat advisories as well as to study possible changes in heat stress due to climate change. However, since this index was not intended to handle higher temperatures that are becoming more common due to global warming, a new version was recently developed. This study uses past U.S. weather data, as well as future climate projections to study the differences between the original and updated indices. It demonstrates that during heat waves, the original version can underestimate heat stress by a considerable amount and urges the adoption of the new index.
Author: John R. Lanzante
Institution: NOAA Geophysical Fluid Dynamics Laboratory
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4403318822