Militaries, like civilian industries, have a profound capacity to pollute the air, land, and water. In the 2010s, U.S. bases in Iraq and Afghanistan disposed of waste in burn pits, resulting in smoke-inhalation-related illnesses among soldiers and civilians.1 In late 2021, a fuel spill at a Hawaiian Naval facility contaminated drinking water, leading to the evacuation of over 90,000 people.2 Incidents like these underscore that military activities can create environmental harm. But how much do global militaries impact the environment, and to what extent are these incidents worsening climate change?
To address these questions, the American Academy of Arts and Sciences convened a roundtable online - “Conflict’s Carbon Footprint: The Hidden Impacts of Modern Wars” - in July 2025. Chaired by Tanisha M. Fazal (University of Minnesota), the event brought together international relations scholars, climate scientists, and policy experts to explore how military operations and installations are contributing to the climate crisis. Speakers described how conflicts amplify emissions and how collaborative research, in partnership with more robust global governance, can improve military emissions reporting and, eventually, decrease pollution.
Estimating Military Emissions
Military emissions must be estimated by researchers because unlike civilian industries, militaries are not legally required to report their emissions, a reporting loophole shaped in large part by U.S. efforts at the 1997 Kyoto and 2015 Paris climate negotiations. During the roundtable, Neta Crawford (University of Oxford), Stuart Parkinson (Scientists for Global Responsibility), and Mykola Shlapak (Initiative on GHG Accounting of War) underscored the imperative of estimating and understanding the massive quantity of greenhouse gases emitted by militaries.
The amount of carbon emitted by militaries is not insignificant. The U.S. military alone emits more carbon annually than any other global military.3, 4 And the U.S. military carbon output is only a portion of all carbon emitted by militaries across the globe. The Conflict and Environment Observatory (CEOBS) estimates that, if all the world’s militaries were a country, they would be the fourth-highest emitter of greenhouse gasses—that’s more emissions than all of Russia.5
Panelists described two categories of military emissions. The first includes direct emissions, like those generated by aircraft fuel use and energy consumption on military bases. The second includes emissions from indirect sources, which can be more difficult to quantify and include things like supply chain logistics, weapons manufacturing, and other contractor activity. The GHG Accounting of War project estimates emissions in both categories using economic modeling of military and contractor spending. Wartime emissions are more complex, as they include additional indirect emissions, like those resulting from post-conflict infrastructure reconstruction, conflict-related fires, displacement and migration, increased healthcare demands, and the re-routing of civilian air traffic around conflict zones.
Speakers noted that military emissions decreased after the Cold War, but recent increases in defense budgets and global geopolitical tensions have reversed this trend. Emissions from war-related activity are now increasing globally. Participants cited predictions that increases in military spending, like NATO’s goal to increase spending by 3.5%, will generate 2,330 million tons of carbon dioxide equivalent (MtCO2e) by 2030, over three times Canada’s annual carbon output, setting back global decarbonization efforts.6, 7
Military Emissions Reporting
While some militaries—including Germany, Norway, the United Kingdom, and the U.S.—have begun to report some of their military emissions, speakers emphasized that reporting is incomplete and inconsistent at best.8 Most militaries report partial emissions associated with day-to-day operations, and few track emissions from their supply chains, contractors, and war-related activity. No military publicizes estimated emissions associated with post-war reconstruction, war-related fires, and survivor health care.9 Most of the world’s highest-spending militaries; including India, Israel, and Saudi Arabia; do not report any emissions data.
Wartime Emissions
Speakers highlighted armed conflict as a major generator of military greenhouse gas emissions, noting that war-related emissions far exceed those generated during non-wartime. They discussed estimated emissions from the ongoing wars in Palestine and Ukraine. A comprehensive February 2025 assessment conducted by the Initiative on GHG Accounting for War estimated that Russia’s war in Ukraine has generated 230 MtCO2e, more than Spain’s annual greenhouse gas output.10 Researchers also estimate that at least 32 MtCO2e, the equivalent of Croatia’s annual emissions, have resulted from the first fifteen months of Israel’s bombardment of Gaza.11 These estimates do not account for the emissions that will result from rebuilding infrastructure that was destroyed during the relevant timeframes.
While discussing strategies to decrease military emissions, participants raised the question of whether increased use of less carbon-intensive military technologies, like drones and cyberattacks, may ultimately reduce the carbon footprint of modern conflicts. Discussants suggested that, while new technologies may emit less carbon, more frequent use of these technologies and the reconstruction that will be required after they are deployed will likely offset any potential emissions improvements.
Governance and Accountability
Speakers emphasized that shifts in military doctrine away from offensive, forward-based strategies and toward more defensive postures will meaningfully reduce emissions and decrease escalatory risks. This would mean fewer training exercises, fewer personnel stationed on overseas bases, and a larger emphasis on strengthening relationships with allies. Participants also emphasized the importance of the international legal system in recognizing, addressing, and deterring war crimes. They expressed hope that prosecuting attacks on civilian oil refineries and power plants as war crimes could help deter such actions, which may protect civilians and prevent the large-scale emissions that such attacks generate.
Participants stressed the importance of integrating military emissions into global emissions reporting and climate policy discussions, including Conference of the Parties (COP) negotiations. Discussants urged one another to apply pressure to international organizations, climate scientists, and political leaders to advocate for improved military emissions monitoring, reporting, and mitigation strategies. They expressed concern that, without a concentrated and coordinated effort, current military spending trajectories will only further intensify, exacerbating an already dire emissions landscape.
The roundtable underscored the value of understanding and decreasing military emissions to both address the global climate crisis and encourage a more transparent and peaceful world.12 Until militaries disclose their greenhouse gas emissions, we will fall short of our climate goals, regardless of civilian environmental efforts. Progress to alleviate the climate crisis will not be possible until the carbon footprint of militaries and their suppliers is addressed.
For more information on the Academy’s climate and security work, contact globalsecurity@amacad.org.