US Defense Secretary Lloyd J. Austin III calls climate change a security issue and an existential threat. He's been clear that "Today, no nation can find lasting security without addressing the climate crisis. We face all kinds of threats in our line of work, but few of them truly deserve to be called existential. The climate crisis does."

According to Brown University's Costs of War Project, the US military is not only threatened by climate change, but it’s also inadvertently contributing to it -- possibly the largest institutional source of greenhouse gas (GHG) emissions in the world. However, it has yet to actually disclose its precise emissions levels due to a design feature of the Paris Agreement that protects sensitive national security information and allows governments to choose what emissions data they want to report.

Why This Matters

The military casts a wide net, encompassing a number of “hard to abate sectors,” like heavy manufacturing, shipping, aluminum, chemicals, steel, cement, and aviation making it even less clear and undisclosed how much the world's largest military actually contributes to GHG emissions.

Scientists for Global Responsibility found that the world's militaries are responsible for about 6% of global GHG emissions. The Costs of War Project hypothesized that the US military emitted 51 million tons of carbon dioxide in 2020, which exceeds the emissions of most countries.

Doug Weir, research and policy director of the UK-based Conflict and Environment Observatory told Nexus Media News: "They're way behind on their shift towards carbon neutrality because they’ve enjoyed this kind of exceptionalism for so long."

Moving Militaries To Decarbonize

Environmental advocacy groups and veterans’ associations alike are calling on militaries to be more transparent about their emissions and start to reduce them more drastically. The Conflict and Environment Observatory released a petition urging governments to do just that, and over 100 international organizations have signed on. At a discussion in June, NATO officials considered setting a target of net-zero emissions for armed forces by 2050.

This year’s budget called for the Pentagon to report on the past 10 years of GHG emissions, but the department missed its July deadline.

Neta Crawford, a political scientist at Boston University and co-director of the Costs of War Project, told Nexus Media News: "we should have information with which to make informed decisions...which could feed into a better outcome."

Not An Army Of One

Secretary Austin is hardly alone. A number of military circles see climate change as a national security threat of huge importance to the Pentagon. Eleven retired military leaders constituting the military advisory board at CNA, a naval think tank in Arlington, described climate change in 2007 as "a threat multiplier for instability." Seven years later, 16 retired flag officers representing all branches of the military implored Americans to understand the severity of "a salient national security concern" because "time and tide wait for no one." Then-Defense Secretary Jim Mattis told the Armed Services Committee in 2017: "Climate change is impacting stability in areas of the world where our troops are operating today."

The American Security Project (ASP) is an organization of retired admirals and generals, who said climate change "is what we call a 'ring road' issue; meaning that climate change affects all of these other threats.... It will change disease vectors. It will drive migration. These changes, in turn, could affect state stability and harm global security."

Some of the defense threats are especially clear. Naval Station Norfolk is the biggest naval installation in the world, and the land that houses it is literally sinking, thanks to uneven ocean temperatures and geology. Sea level rise could be devastating for this base or for the US Navy fleet, 20% of which is home-ported nearby.