Climate change impacts on the U.S. Army basic combat training program

Abstract

Heat illness in the U.S. Army recruit training population is a significant risk leading tolost training time, hospitalization, failure to graduate basic training, or death. To protect this population, the wet bulb globe temperature (WBGT) thermal index is recorded during periods of hot weather and a five-tiered activity modification scale is applied. While activity modification is protective for the recruit population, during extended periods of high WBGT anticipated in the near future, such activity modification will disrupt the tightly scheduled basic training program. There are four U.S. Army basic training installations. At each, climate change is increasing the frequency and duration when WBGT exceeds the top two activity modification thresholds, but impacts are variable across each installation. Understanding the local impacts of climate change on WBGT is necessary to assess how future basic training classes will be affected. The limited number of prior studies projecting future WBGT trends suffer from spatiotemporal resolution challenges or make assumptions that limit their applicability to the type of localized impact-assessment study required to understand climate change’s impact on basic training programs. This dissertation presents a climate change impact assessment for the US Army basic training program by considering how WBGT changes affect each installation where training is conducted. I first analyze historical WBGT trends at basic training installations using statistical methods to quantify trends according to the WBGT thermal index. I then develop a novel method to project future WBGT trends using a combination of historical records and high-resolution climate model output from a NASA database. A subset of climate models for each location is selected based on skill at recreating historical WBGT distributions and then bias adjusting the outputs. The resulting WBGT projections are at high spatial and temporal resolution and suitable v for use in assessing impacts to basic training installations. I apply these projections to evaluate how the reoccurrence of hot WBGT extremes changes at each installation between 2025-2100 according to several metrics and provide an assessment of how specific attributes of the recruit training program will be affected by mid-century. Finally, I conclude with an expanded assessment of how temperature extremes will affect future Army training and operations in the coming decades more generally. The findings of this dissertation have implications for the U.S. Army but can be broadly applied to any outdoor labor program that regulates activity modification according to the WBGT index, particularly programs that are highly scheduled and sequenced. For example, construction, agricultural, public safety, and athletics programs will find this method useful in evaluating location-specific impacts of climate change. Through the main chapters of this dissertation, recommendations are made to mitigate the effects of increasing extreme WBGT, providing a starting point for implementing adaptations that will be required in coming decades.