Code from: Analysis of observed warming trends at U.S. basic combat training installations and consideration of implications for future recruit training

Introduction: Army recruits conducting basic combat training (BCT) are among the most susceptible population of military personnel to experience exertional; heat illness, a concern expected to become increasingly urgent due to steadily rising temperatures. In this study, we provide an empirical analysis of wet bulb globe temperature (WBGT) trends at U.S. Army basic combat training installations and quantify the magnitude of these trends. Assuming these warming trends continue, the anticipated effects of increasing temperature trends are discussed in relation to potential impacts to recruit heat illness incidence and potential training disruption.

Materials and Methods: We obtained weather data beginning in the early 1960s, including wet bulb globe temperature measurements derived by the U.S. Air Force 14th Weather Squadron. We apply these datasets to two classifications for high WBGT days, including one classification accounting for heat illness susceptibility based on prior day heat exposure, to determine when recruits are most at risk of heat illness. The daily likelihood of extreme WBGTs are described at each installation using a thirty-year climatological average. Trends in WBGT are evaluated quantitatively during the warm season (May 1st -September 30th) and full year and compared between decades and by individual BCT classes.

Results: Trends in WBGT have increased at all four basic combat training installations. The average (mean) WBGT is increasing fastest at Ft Jackson, SC (0.272°C, CI: 0.255-0.289) and slowest at Ft Moore, GA (0.190°C, CI: 0.170 – 0.210). Ft Moore experiences the highest heat burden, with the likelihood of experiencing a “black flag” temperature event peaking at nearly 50% in late July, while Ft Leonard Wood, MO, experiences the least. Heat burden is spread unevenly across installations and dependent on class start date. Recruits beginning in mid-June will experience approximately 200 hours of hazardous heat if training at Ft Moore, GA, 100 hours and 80 hours at Ft Jackson, SC, and Ft Sill, OK, respectively, and 61 hours at Ft Leonard Wood, MO.

Conclusions: In the future, adaptation to the basic combat training program will be required to maintain rigorous standards without incurring unacceptable risk of recruit heat illness. The trends and analysis provided by this study can help inform medical, training, and policy implementations needed to ensure continued basic combat training in a warming world.