If I were to tell you that there were nearly 2,800 cases of heat-related illness among active-duty members of the US military last year, you might not be surprised. After all, we have troops deployed throughout the Middle East, where some of the world’s hottest places are found. But what if I were to tell you that of those thousands of cases, only 67 occurred among troops deployed in Iraq and Afghanistan? It turns out that right here at home in the US, thousands of servicepeople suffer from heat-related illnesses like heat exhaustion and heat stroke every year, and the problem is set to grow much worse.
We used data from our recent Killer Heat report to analyze how the frequency of days with dangerous heat at sizable Air Force, Army, Marine Corps, and Navy installations in the contiguous US is projected to change in the coming decades. Our results show that with no action to reduce global heat-trapping emissions, on average, by midcentury US installations would experience nearly five times as many days with a heat index above 100°F as they have historically. These results imply that living, working, and training at US military bases is poised to become increasingly risky for servicepeople and their families over the course of the next few decades and in every branch of the armed forces.
The overall rate of heat stroke among servicepeople (red line) has nearly doubled for the Armed Forces as a whole. The increase has particularly affected the Marine Corps and Army.
Heat-related illness rates on the rise in the military
The military maintains detailed records of the incidence of heat illness and publishes those statistics in an annual report. This year’s report, summarizing data from 2014 through 2018, notes that the number and rate of heat-related illnesses has risen substantially over the last five years and concludes that “heat illnesses are a significant and persistent threat to both the health of U.S. military members and the effectiveness of military operations.” Moreover, it notes that roughly 40% of heat illness cases over the last five years have occurred on just five populous US military bases, all located in the Southeast region: Fort Benning, GA; Fort Bragg, NC; Marine Corps Base Camp Lejeune/Cherry Point, NC; Fort Campbell, KY; and Fort Polk, LA.
Statistics reported by the military in April, 2019, show that the number of cases of heat-related illness has risen by about 50% over the past five years.
With some excellent reporting this past summer, NBC and InsideClimate News extended the military’s data back to 2007, which puts the increase over the last few years into perspective and makes clear that the Army and Marines have experienced the biggest increases.
Detailed statistics for 2018 and 2017 paint a picture of very uneven risk among different military demographics. The rate of heat-related illness among recruits–the newest and typically youngest members of the military–for example, is six times higher than the rate for enlisted members. Servicemembers under the age of 20 experience three times as much heat illness as those ages 20-24. This likely reflects a lack of acclimation to heat conditions among newer members of the military. An older data set similarly indicates that recruits from northern states suffer higher rates of heat illness than recruits from southern states.
Racial and ethnic demographics also define subgroups with elevated rates of heat-related illness: Asian and Pacific Islander and, to a lesser extent, non-Hispanic black servicemembers also experience higher rates of heat-related illness than their white or Hispanic colleagues. While the 2017 and 2018 data reports don’t offer any clues as to why this might be, it is well-documented that non-whites in the general population are more likely to experience extreme heat and related health impacts as a result of generations of systematic racism that have left them with fewer resources–both physical and financial–to cope with heat.
Our analysis of extreme heat at military bases
The data underlying our analysis of how the frequency of extreme heat is projected to change at US military bases comes from our Killer Heat report, published earlier this year. For that report, we used data from 18 high-resolution climate models to calculate how often the heat index, also known as the “feels like” temperature, would exceed 90°F, 100°F, or 105°F in the future in response to changes in human emissions of heat-trapping gases. Given the relative fitness of military servicepeople and the fact that their training can involve intense physical exertion, we focus on days that exceed a heat index threshold of 100°F for this analysis.
Using geographic information on the location of military installations from the Census Bureau, we extracted that frequency data for every installation in the contiguous US–roughly 760 in all. We then narrowed our analysis to the roughly 170 installations with a population of 1,000 or more active duty servicemembers based on 2015 statistics from the Department of Defense’s Base Structure Report. (Note that no Coast Guard installations have a population of 1,000 or more; they are thus excluded from this analysis.)
We found that by midcentury, with no action to reduce global emissions, sizable military installations in the US would, on average, experience an additional 33 days per year with a heat index above 100°F. For some bases, however, the increase is much larger. Fort Sill in Oklahoma, for instance, is projected to experience an additional 53 days per year of dangerous heat by midcentury. And in cases like Luke Air Force Base in Arizona, the heat would be much more extreme: an additional 17 days per year with a heat index above a scorching 120°F.
Historically, only nine major military installations in the US have experienced 30 or more days per year with a heat index above 100°F. By midcentury, with no action to reduce emissions, 100 installations would experience such conditions.
| Installation | Historical | Midcentury | Increase |
| Homestead Air Reserve Base, FL | 13 | 115 | 102 |
| MacDill Air Force Base, FL | 20 | 116 | 96 |
| Naval Air Station Pensacola (Corry Station), FL | 6 | 84 | 78 |
| Naval Air Station Pensacola (Outlying Field Bronson), FL | 6 | 83 | 77 |
| Naval Air Station Joint Reserve Base New Orleans, LA | 23 | 97 | 74 |
| Hurlburt Field, FL | 7 | 80 | 73 |
| Keesler Air Force Base, MS | 13 | 86 | 73 |
| Naval Construction Battalion Center Gulfport, MS | 19 | 91 | 72 |
| Fort Sam Houston, TX | 31 | 101 | 70 |
| Lackland Air Force Base, TX | 36 | 105 | 69 |
Dangerous heat at basic training installations
Across all of the branches of the Armed Services–excluding the Coast Guard–there are just eight installations where basic training happens. These installations serve between 6,000 and 22,000 troops, and the majority are located in places that are already relatively hot. By midcentury, with no action to reduce global carbon emissions, basic training facilities are projected to experience an average of an additional six weeks per year with a heat index above 100°F.
By midcentury, six of the eight basic training facilities in the nation would experience at least 30 days with a heat index above 100°F.
| Installation | Historical | Midcentury | Increase |
| Lackland Air Force Base, TX | 36 | 105 | 69 |
| Marine Corps Recruit Depot Parris Island, SC | 16 | 73 | 57 |
| Fort Benning, GA | 16 | 73 | 57 |
| Fort Sill, OK | 20 | 73 | 53 |
| Fort Jackson, SC | 13 | 59 | 46 |
| Fort Leonard Wood, MO | 8 | 53 | 45 |
| Naval Station Great Lakes, IL | 2 | 16 | 14 |
| Marine Corps Recruit Depot San Diego, CA | 0 | 0 | 0 |
Dangerous heat at Air Force installations
On average, with no action to reduce emissions, the Air Force installations we analyzed would experience an additional 34 days per year with a heat index above 100°F by midcentury. More than half of the Air Force bases we analyzed (43 of 77 total) would experience the equivalent of a month or more of these dangerous conditions by midcentury compared with just six historically. Five installations–including Lackland Air Force Base, the branch’s only basic training facility–are projected to experience 100 or more days per year with a heat index above 100°F.
By midcentury, more than half of sizable Air Force installations in the nation would experience 30 or more days with a heat index above 100°F if we take no action to reduce global carbon emissions.
| Installation | Historical | Midcentury | Increase |
| Homestead Air Reserve Base, FL | 13 | 115 | 102 |
| MacDill Air Force Base, FL | 20 | 116 | 96 |
| Hurlburt Field, FL | 7 | 80 | 73 |
| Keesler Air Force Base, FL | 13 | 86 | 73 |
| Lackland Air Force Base, TX | 36 | 105 | 69 |
| Laughlin Air Force Base, TX | 30 | 99 | 69 |
| Randolph Air Force Base, TX | 31 | 100 | 69 |
| Patrick Air Force Base, FL | 4 | 72 | 68 |
| Tyndall Air Force Base, FL | 8 | 76 | 68 |
Dangerous heat at Army installations
Of the 169 installations we analyzed, 36 are Army bases. Historically, only two of those installations have experienced 30 or more days with a heat index above 100°F in an average year. But by midcentury, 27 of those installations would experience such heat if we take no action to reduce global emissions.
With no action to reduce emissions, by midcentury three-quarters of the sizable Army installations in the contiguous US would experience 30 or more days per year with a heat index above 100°F.
| Installation | Historical | Midcentury | Increase |
| Fort Sam Houston, TX | 31 | 101 | 70 |
| Camp Swift, TX | 37 | 104 | 67 |
| Fort Polk, LA | 27 | 94 | 67 |
| Fort Hood, TX | 25 | 90 | 65 |
| Fort Stewart, GA | 28 | 92 | 64 |
| Fort Rucker, AL | 15 | 75 | 60 |
| Fort Benning, GA | 16 | 73 | 57 |
| Camp Joseph T. Robinson, AR | 25 | 79 | 54 |
| Fort Sill, OK | 20 | 73 | 53 |
| Fort Campbell, KY | 10 | 61 | 51 |
Many of the Army’s most populous installations would face significantly more than 30 days per year of these dangerously hot conditions. For example, Forts Benning and Stewart in Georgia, which each have populations of more than 22,000, are projected to experience the equivalent of two to three months’ worth of days with a heat index above 100°F by midcentury compared with less than one month per year historically.
Dangerous heat at Marine Corps installations
Just ten Marine Corps installations have a population of at least 1,000 troops, so only ten were included in our analysis. Historically, only one Marine Corps installation–Marine Corps Air Station Yuma in Arizona–has experienced more than 30 days with a heat index above 100°F in an average year. By midcentury, six of those ten installations would experience such heat if we take no action to reduce global emissions.
Overall, Marine Corps installations would face an average of an additional 32 days per year with a heat index above 100°F by midcentury with no action to reduce emissions. But in many cases, the increase is much steeper. For example, with just 11 days per year with a heat index above 100°F historically, Camp Lejeune already has among the highest number of heat-related illness cases. By midcentury, with no action to reduce emissions and assuming no population change, the 40,000 troops stationed at Lejeune would be subject to the equivalent of more than seven weeks per year with a heat index above 100°F.
With no action to reduce global emissions, six of the ten sizable Marine Corps installations in the contiguous US would experience 30 or more days per year with a heat index above 100°F.
| Installation | Historical | Midcentury | Increase |
| Marine Corps Recruit Depot Parris Island, SC | 12 | 73 | 61 |
| Marine Corps Air Station Beaufort, SC | 15 | 74 | 59 |
| Marine Corps Base Camp Lejeune, NC | 11 | 57 | 46 |
| Marine Corps Air Station Cherry Point, NC | 8 | 52 | 44 |
| Marine Corps Air Station Yuma, AZ | 76 | 117 | 41 |
| Marine Corps Base Quantico, VA | 5 | 38 | 33 |
| Marine Corps Air Ground Combat Center Twentynine Palms, CA | 1 | 26 | 25 |
| Marine Corps Air Station Miramar, CA | 0 | 5 | 5 |
| Marine Corps Recruit Depot San Diego, CA | 0 | 0 | 0 |
Dangerous heat at Navy installations
Of the 169 installations we analyzed, 31 are Navy bases. Historically, none of those installations have experienced 30 or more days with a heat index above 100°F in an average year. By midcentury, more than half of those installations (17) would experience such heat if we take no action to reduce global emissions.
Many of the Navy’s most populous installations, such as Naval Air Station and Joint Reserve Base Fort Worth in Texas (population: 7,575) would face the equivalent of two months per year with these dangerously hot conditions.
By midcentury, with no action to reduce global emissions, more than half of the sizable Navy installations in the contiguous US would experience 30 or more days with a heat index above 100°F.
| Installation | Historical | Midcentury | Increase |
| Naval Air Station Pensacola (Corry Station), FL | 6 | 84 | 78 |
| Naval Air Station Pensacola (Outlying Field Bronson), FL | 6 | 83 | 77 |
| Naval Air Station Joint Reserve Base New Orleans, LA | 23 | 97 | 74 |
| Naval Construction Battalion Center Gulfport, MS | 19 | 91 | 72 |
| Naval Station Mayport, FL | 8 | 74 | 66 |
| Whiting Pines Off Base Military Housing, FL | 15 | 79 | 64 |
| Naval Air Station and Joint Reserve Base Fort Worth, TX | 29 | 90 | 61 |
| Naval Submarine Base Kings Bay, GA | 12 | 73 | 61 |
| Naval Air Station Lemoore, CA | 14 | 56 | 42 |
| Norfolk Naval Shipyard, VA | 9 | 42 | 33 |
How does the military currently keep troops safe from extreme heat?
The Air Force, Army, Marine Corps, and Navy all have rigorous heat protection standards in place. These standards vary somewhat from branch to branch, but generally they rely on assessments of both the physical workload and the Wet Bulb Globe Temperature–a metric similar to the heat index that incorporates temperature, humidity, wind speed, and exposure to direct sun–to categorize conditions. Work/rest schedules and hydration requirements then follow from those categories.
Noting the rise in heat illness among US troops despite those rigorous standards, the Army recently announced a “Heat Center” initiative at Fort Benning, Georgia, that is intensely focused on managing, preventing, and researching heat illness. Since the center’s inception, Fort Benning, which had in recent years led the nation’s installations in the number of heat illness cases, has not had any heat-related deaths–an encouraging sign of progress.
How can we prevent heat illness in the military in the future?
With troops deployed around the world in a wide range of environments, our troops need to be sufficiently prepared to operate under extreme climate conditions. Yet thousands of servicepeople suffering from heat illness on our home soil is clearly a problem, and it’s one the military is well aware of.
In light of the growing risks our analysis identifies, heat-related health guidelines across all branches of the Armed Services should be reviewed and updated to reflect current risks and projections of worsening heat. Military personnel, especially those in command, should be trained to be more fully aware of the dangers of heat-related illnesses, and safeguards around work/rest cycles should be diligently enforced to prevent over-exertion on dangerously hot days. Relatively inexperienced recruits, who may be particularly at risk because they may not recognize warning signs or may feel that they have to “push through” tough conditions, should be carefully monitored. Medical protocols and best practices can help ensure that personnel who fall ill due to extreme heat quickly get the care they need. Innovations in clothing, equipment, and other technologies may also help keep servicepeople cooler. Even with these measures, the military may need to adjust the times of day or times of year when it is safe to conduct training activities requiring serious exertion.
Extreme heat will also affect military families living on bases. Housing, schools, clinics, and community centers will also need to be upgraded to keep people safe during dangerously hot days.
Climate change will increasingly threaten our national security military readiness in many ways, from threatening our coastal infrastructure to the growing incidence of extreme heat here and around the world. By swiftly and aggressively reducing our carbon emissions and contributing to global efforts to limit climate change, and by strengthening the military’s protocols for preventing and addressing heat-related illness, we can ensure that our troops are positioned to meet this threat rather than fall victim to it.