Come Hell or High Water: The Pentagon’s Posture toward Climate Change


By now, most people have heard much about the implications of President Donald Trump’s decision to withdraw from the Paris Agreement. They have heard critics denounce the dismissive message this sends about a global crisis and the implications for U.S. global leadership at international fora addressing the issue. They have heard Trump say it was a bad deal and that it was going to have a negative impact on American jobs (despite being non-binding).

But are there any implications of this move for the Department of Defense? Not directly, though there will be indirect consequences as it engages international partners.

Trump’s decision creates more tension across the international environment in which the United States must work. Our allies in militaries across the world are likely to be able to compartmentalize the fact that Washington isn’t the partner it could be in addressing this global crisis, but they will also be aware that Trump thumbed his nose at them. This snub may make America’s allies less willing to cooperate with or trust the United States, which in turn makes the Defense Department’s job harder than it needs to be. Trump’s decision will create a leadership void in the international community that could provide an opportunity for nations like China to gain more global influence. In sum, the strategic environment is now more challenging, and that will make the Defense Department’s mission more challenging as well.

Beyond these serious strategic concerns, however, withdrawal from this agreement should not change the Defense Department’s posture toward climate change.

I was acting as the assistant secretary of defense for energy, installations, and environment when the Paris Agreement was signed in 2015, and the Pentagon neither took nor was required to take any action in response. Accordingly, there are no actions the department would have to reverse upon withdrawal from the agreement. In my experience, the department is driven by mission and adaptation. Regarding emissions reductions, the Pentagon’s approach has been more focused on energy efficiency and renewable energy efforts that save the department money and make the U.S. military more effective.

Secretary Jim Mattis has been very clear that climate change affects his department’s mission, and to the extent that it does, it must be considered. Specifically, he responded to Congressional questions for the record following his confirmation hearing, stating:

I agree that the effects of a changing climate — such as increased maritime access to the Arctic, rising sea levels, desertification, among others — impact our security situation. I will ensure that the department continues to be prepared to conduct operations today and in the future, and that we are prepared to address the effects of a changing climate on our threat assessments, resources, and readiness.

Speaking about the direct implications for our troops in the field, he said:

Climate change is impacting stability in areas of the world where our troops are operating today. It is appropriate for the Combatant Commands to incorporate drivers of instability that impact the security environment in their areas into their planning … Climate change can be a driver of instability and the Department of Defense must pay attention to potential adverse impacts generated by this phenomenon.

In other words, the Department of Defense cares about climate change because it affects its mission, and the DoD is committed to being able to carry out that mission. This is a distinctly apolitical and pragmatic perspective.

So if, according to Mattis, the Department of Defense must pay attention to the potential adverse impacts of climate change, then it must consider the impacts of food and water scarcity and how they drive instability in the Middle East. It must consider how the melting of Arctic ice thaws Russian ports, clears northern sea lanes, and drives increased resource extraction activity. And it must consider plans responding to climate-driven disasters and the instability they may cause.

In addition to planning for impacts to missions around the world, the Department of Defense has been assessing the vulnerability of its installations to climate changes. With more than 500 major installations spread around the world, the Department of Defense faces challenges rooted in climate change. These include recurrent flooding driven by sea-level rise, erosion near critical surveillance stations in the Arctic accelerated by the disappearance of coastal ice and snow, drought at its bases in the southwest, and the need to improve resilience to power outages driven by intense storms. Moreover, droughts and wildfire risk affect training and readiness by restricting the use of live munitions. High heat days impose limits on the exertion one can require of troops. As the Department of Defense prioritizes readiness, it is being forced to adapt to these changes as well.

So despite Trump’s predictable fulfillment of a campaign pledge to withdraw from the Paris Agreement, the Department of Defense will continue to take climate risks into account as it contemplates current and future missions. Mission requirements will drive the Pentagon to pursue energy efficiency or to leverage renewables to improve energy resiliency, even if there are no emissions goals. Mattis will continue to support the enhancement of his force’s readiness in the face of flooding, drought, storm resilience and increased instability.

The bottom line for the Department of Defense is that it has a job to do, and it is going to accomplish it come hell, high water, or any other change in the climate.


John Conger is a Member of the Advisory Board of the Center for Climate and Security.  He is the former Principal Deputy Under Secretary of Defense (Comptroller) and the former Acting Assistant Secretary of Defense (Energy, Installations & Environment).