The True Cost of Heat: Evaluating Heat-Related Mortality Estimation Methods in Texas

Abstract

Different ways of counting heat-related deaths (HRD) can give you very different numbers. This study examines HRD in Texas using three different definitions: The Optimal Temperature Method (OTM) estimates mortality based on deviations from a community's optimal temperature, capturing the effects of both moderate and extreme heat exposure. This method finds that 2.2% of summertime Texas mortality were heat related over the period 2010–2023. The Extreme Heat Method (XHM) counts deaths associated with extreme temperatures; we find that temperatures exceeding the 95th percentile were responsible for 0.5% of summertime Texas mortality over this same period. This means that moderate heat is responsible for 77% of HRD, with extreme temperatures responsible for the rest. The Excess Death Method (EDM) approach quantifies the mortality burden as the increase in mortality compared to what would have occurred with the climate of a baseline period; we find that summertime Texas mortality over this period was 1.7% higher than with the climate of the mid-20th century. When comparing these estimates to official HRD values from the State of Texas, which are based on an official determination that heat contributed to the death, we find that official State HRD numbers appear to substantially underreport HRD, attributing just 0.3% of summertime deaths to heat, with the XHM method being the closest.