A new study led by Ryan Thombs of Penn State University reveals that the U.S. Department of Defense (DoD) is the largest institutional emitter of greenhouse gases globally, underscoring the military’s outsized role in driving climate change. Published in PLOS Climate on July 2, the research links the DoD’s vast global operations—ranging from base maintenance and training exercises to weapons transport and R&D—with significant energy consumption and carbon output.
The study comes amid growing acknowledgment from military leaders themselves that climate change is a critical threat to national and international security. Yet, the emissions footprint of military activity has remained understudied in climate policy circles.
Using publicly available data from 1975 to 2022, Thombs and his team conducted a comprehensive analysis of U.S. military spending and corresponding energy use. Their findings show a clear pattern: reductions in defense spending consistently lead to reductions in energy consumption—particularly in jet fuel, vehicles, equipment, and facility operations.
Notably, the study found that cutting military spending has a more substantial impact on reducing energy use than increases in spending have on raising it, suggesting an asymmetric relationship. In other words, even modest defense budget cuts could yield disproportionately large climate benefits.
The researchers also projected various scenarios from 2023 to 2032. If the U.S. were to implement sustained cuts to military spending, the resulting energy savings by 2032 could match the entire annual energy consumption of the U.S. state of Delaware or the country of Slovenia.
Despite the size and scope of the military’s carbon footprint, few previous studies have directly analyzed how defense budgets correlate with energy usage. This research helps fill that gap and calls for deeper exploration into how military policy and climate action intersect.
“Our findings suggest that curbing U.S. military spending offers a practical and impactful way to reduce fossil fuel consumption and combat climate change,” the authors concluded.
