A new study has unveiled the significant carbon footprint of the US military, indicating that even modest budget cuts can lead to substantial reductions in emissions.

Published in the journal PLOS Climate, the study reveals a strong correlation between spending by the US Department of Defense (DOD) and energy consumption, along with greenhouse gas emissions. The authors assert that lowering military expenditures could result in considerable environmental benefits.

The US military stands as the largest emitter of greenhouse gases globally, with an estimated output of 636 million tonnes of CO2 equivalents (a standard measure for greenhouse gas emissions) recorded between 2010 and 2019.

In fact, if the military were classified as a country, its emissions would surpass those of nations like Sweden and Portugal.

Moreover, this data only considers scope 1 and 2 emissions, which are the direct emissions from fuel combustion and purchased electricity. Indirect emissions (scope 3) from factors such as employee travel, waste disposal, and supply chains are not included, indicating that the military’s actual carbon footprint is even larger.

Utilizing public data from 1975 to 2022, Professor Ryan Tomb of Penn State University has examined the relationship between military spending, energy consumption, and consequently greenhouse gas emissions.

As expected, increased military spending leads to higher energy usage, while budget cuts result in decreased consumption. Interestingly, the study found that the reduction in spending had a more pronounced effect on energy consumption than increases did.

“Our findings show that spending reductions correlate with lower energy use, particularly from military facilities, vehicles, equipment, and jet fuel,” Thombs stated in an interview with BBC Science Focus.

“Although further research is required to explore specific mechanisms, these results imply that cutting spending may compel the military to diminish the scale, distance, and frequency of operations more than increased spending would push for expansion,” he added.

Another potential reason for this trend could be that budget cuts may disproportionately limit aviation activities.

Globally, military jets rank among the most energy-intensive machines. In the US military, jet fuel has accounted for 55% of total energy usage over the last fifty years.

“Given the substantial share of energy consumption, prioritizing a reduction in aviation activities is critical,” Thombs commented. “Aviation is highly energy-intensive, and serious efforts to lessen military emissions should target this area.”

It is widely acknowledged that controlling aviation emissions is challenging. Both military and commercial aviation are often described as “hard-to-abate” sectors that cannot yet transition away from fossil fuels at the scale and energy density currently required.

This suggests that curtailing aviation operations is essential for achieving emissions reductions, according to Thombs.

The research team also outlined projections for various future budget scenarios. They discovered that if military spending were to decrease by 6.59% annually from 2023 to 2032, the DOD could save energy equivalent to the entire energy usage of Slovenia or Delaware. This represents a feasible reduction rate observed over the last 50 years, making it a plausible target.

While the scientific rationale is evident, the political landscape tells a different story. Governments worldwide are increasingly escalating their defense budgets amid a climate fraught with conflict and instability.

On June 26th, President Trump’s administration proposed a $1.01 trillion National Defense Budget for the upcoming fiscal year, marking a 13.4% increase from the previous year.

Despite this trend, Thombs remains hopeful. He believes that with the right framing, it is possible to achieve spending reductions. He pointed to previous proposals by Senators Edward Markey and Bernie Sanders to cut military spending by 10%, redirecting those funds toward jobs, healthcare, and education.

“Framing these reductions in such a manner could be an effective strategy, as reinvesting these resources could significantly enhance people’s lives,” Thombs remarked. “Ultimately, the most effective way to mitigate the social and environmental costs associated with the military is to scale it back.”

Researchers are currently planning to explore why spending cuts yield such exceptional energy savings and whether this trend holds for other major military forces.

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About our experts

Ryan Tomb serves as an assistant professor of rural sociology in the Faculty of Agricultural Economics, Sociology, and Education at Penn State University in the United States. His published research appears in American Sociological Review, Sociological Methodology, Journal of Health and Social Behavior, and Society, along with interdisciplinary journals such as Changes in the Global Environment, Energy Research and Social Sciences, Climate Change, and Environmental Survey Letters.