How the Defense Department Can Move from Abstraction to Action on Climate Change

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One week after he was sworn in as president, Joe Biden directed his secretary of defense to make climate change a central priority. The president’s executive order instructed the Department of Defense to work with an interagency group over the next 120 days to create a first-of-its-kind joint “Climate Risk Analysis,” and determine the implications of that analysis for the “National Defense Strategy, Defense Planning Guidance, Chairman’s Risk Assessment, and other relevant strategy, planning, and programming documents and processes.” Secretary of Defense Lloyd Austin affirmed the department’s intent to execute those orders, and to report back annually to the National Security Council on its progress. He also announced a new Department of Defense Climate Working Group chaired by a special assistant to the secretary of defense. After joining the first meeting of that working group, Deputy Secretary of Defense Kathleen Hicks publicly stated that “confronting climate challenges is mission critical,” which carries substantial weight given her central role in directing the Defense Department’s internal processes.

The Defense Department and the broader U.S. national security apparatus have since at least the early 1990s recognized climate change as a primary strategic threat shaping the security environment. However, relatively little has been done to address the overall implications of climate change through changes in strategy, planning, and resources.



Senior defense officials need to translate the abstraction of the climate threat into decisions that meaningfully address cascading risks. The best way to do that on an accelerated basis is to convene a high-level tabletop exercise in order to make an abstract concept like climate change seem more concrete. Tabletop exercises have proven utility in generating a common picture of the future among leaders to inform decisions and highlight tradeoffs. These exercises also highlight new perspectives across the defense enterprise that can inform overall strategy. Moreover, they are a low-risk learning opportunity for participants to understand gaps in existing knowledge and institutional capacities.

Enduring Obstacles

The two key challenges to climate action at the Defense Department are the complexity of accurately modeling future risks and the deteriorated state of the department’s strategic foresight capabilities. The department will need to translate complex forecasts on the environmental impacts of climate change to issues that affect the Department of Defense mission set, such as regional conflicts, force readiness, and humanitarian and disaster relief at home and abroad.

While the scientific forecasts surrounding the planetary consequences of climate change are increasingly precise and data-informed, explaining how the changing climate will lead to changes in international security is extremely difficult. Understanding the second- and third-order effects of climate change — where much of its damage will be wrought from a defense standpoint — becomes a highly complex endeavor and demands a fundamentally different way of understanding risks, especially for military planners. The Defense Department can expect to receive support from the intelligence community in thinking through these problems. However, Erin Sikorsky — a former deputy director of the Strategic Futures Group on the National Intelligence Council — recently argued that the intelligence community’s inadequate organization and resourcing to analyze the threat makes this task more challenging.

For more than a decade, the Defense Department has studied how climate will affect the viability of military installations and the military’s carbon footprint. Climate was elevated as a strategic priority under the Obama administration, with detailed mentions in both the 2010 and 2014 Quadrennial Defense Reviews, the 2014 Climate Change Adaptation Roadmap, and the creation of the Office of the Assistant Secretary of Defense for Operational Energy. Even during the climate-denial era of the Donald Trump administration, some limited progress was made. Despite a National Defense Strategy that made no mention of “climate change,” there was continued recognition across the Department of Defense that it would need to manage the threat to military installations and operational readiness posed by the threat. Congress also has been increasingly active on the topic, with explicit reference to climate change threats in the past three National Defense Authorization Acts and directed studies. None of these efforts, however, tackle the sprawling complexity of the climate challenge.

Now, the White House is pushing the department to go further by focusing on how climate change will affect everything the joint force needs to prepare for. The good news for Defense Department leaders is that while they may be scrambling to answer the novel guidance they’ve been given, important and serious work has been done on this topic for more than a decade by the broader policy community. For example, CNA’s 2007 and 2014 Military Advisory Board — under the direction of former Deputy Undersecretary of Defense (Environmental Security) Sherri Goodman — identified a range of concrete potential considerations. These included accelerating preparations for military operations in the arctic, integrating climate impacts into the National Infrastructure Protection Plan, and conducting comprehensive assessments of climate impacts on mission and operational resilience.

However, climate action in the Defense Department could become mired in its bureaucracies’ underperforming strategic foresight process, including the fragmented Analytic Agenda and Defense Planning Scenarios and its suboptimal use of wargames. This will take some time to fix. Embedding considerations of climate change from the 120-day review into this process will be an even tougher task. A tabletop exercise (or series of exercises) can serve as a bridge while these slower processes catch up with an increasingly urgent problem.

Lessons From Climate Change Tabletop Exercises

The Defense Department should host a series of tabletop exercises to explore implications of climate change for future force readiness, contingency operations, and resilience. The series should be designed around a single, compelling scenario and ideally run on a repeat basis with multiple audiences. However, the first exercise should be optimized for the high-level members of the Climate Working Group.

The tabletop exercises would help senior leaders build a common, more concrete understanding of how climate challenges will affect the Department of Defense and its particular responsibilities within the enterprise. For busy leaders coping with multiple issues, a tabletop exercise can afford an immersive, uninterrupted learning experience. Certainly, it is not meant to substitute for the years of work ahead to implement the intent of the Biden administration’s guidance on addressing climate change as a national security threat. And it ought to be taken in tandem with the ongoing 120-day assessment of climate risks as a foundation for the department’s overall climate efforts.

We speak from firsthand experience. The Center for Strategic and International Studies used tabletop exercises at its annual Global Security Forum this past September. One of the three scenarios considered by participants was the effects of runaway climate change using the tabletop exercise format. We posited a very challenging future scenario of compounding first- and second-order consequences of climate change, and asked questions about the interests at stake, the tools the United States and its allies and partners had to meet the challenges at hand, and how to take actions today that could reduce future risks. The tabletop exercise proved immediately useful in helping illuminate future uncertainty through structured dialogue without the need to toil endlessly in “exactly” forecasting the future.

The “2030 scenario” used at the event — a once-in-a-1,000-year drought precipitating shortages in key agricultural commodities and a migration crisis on the southern border, with much of the rest of the world similarly reeling — helped illustrate, quite vividly, the complexities of climate change as a national security threat. It also revealed several weaknesses in U.S. government and international coordination mechanisms and in existing security paradigms.

The broader benefit from this exercise was its effect on participants’ imaginations. Back-casting from a scenario — that is, positing a potential future and asking what specific steps would have to be taken today to create or avoid that future — helped shift from an understanding in the abstract that climate change is a “threat multiplier” to understanding how it might strain future force readiness for overlapping contingency operations.

The scenario used during the exercise was far from a worst-case scenario, yet its deep and broad consequences took several experts by surprise. The multidimensional nature of cascading crises was particularly challenging for participants to take on all at once. The many unprecedented ways in which climate change is likely to affect the national security environment and Department of Defense capabilities requires imaginative thinking and exercises that push analysts and leaders alike out of their comfort zones and frames of reference.

The first clear takeaway from the tabletop was how no single participant was an expert in the overlapping and interconnected issues raised by the exercise. Challenges of migration, global food security, and border security cut across different areas of expertise and made prediction of consequences more difficult. Many climate experts have devoted their attention to mitigation alone, while few resilience experts were sufficiently versed in global food security issues, for example, to be able to predict the consequences of a wheat shortage in North America. Where the phrase “whole-of-government” is thrown around a lot in climate conversations, the exercise painted a vivid portrait of why greater bureaucratic collaboration has to be a strategic priority.

Second, in a world of increasingly dire and compounding climate change effects, environmental issues shift from being moral concerns in developed nations to national security issues with global consequences. A drought of Dust Bowl proportions would likely create a humanitarian as well an ecological crisis in the United States, and could open windows of opportunity for adversaries and non-state actors to “weaponize” natural resources like water and agricultural staples like wheat. In our scenario, Russia withheld wheat from global markets to drive a wedge between U.S. allies, transforming an environmental disaster into a geopolitical crisis.

Next, issues of significant national security consequence in the future are in the hands of slow-moving international discussions such as the U.N. Climate Change Conference. For example, in the scenario we considered, millions of displaced persons raised the likelihood of conflict around the world by 2030. This was partly a result of countries’ failure to negotiate robust global frameworks for climate migrants and refugees over the preceding decade. By and large, the national security establishment has paid scant attention to these issues, and many of these negotiations languish in semi-permanent limbo without the heightened attention and political consensus that a security focus can bring.

Similarly, the imperative of economic development in low-income countries, particularly in Latin America, takes on even greater strategic implications for the United States in a world of regular natural disasters, resource scarcity, and other vectors of instability. The scenario considered in our tabletop exercise clearly illustrated the dangers of failing to invest in Mexico’s adaptation capacity, for example, with local authorities essentially ceding control of its northern border to organized crime syndicates. Development has long been cast as a national security issue, though the links between conflict and economic security are often fuzzy at best. Over time, climate change will cast these links into sharper relief.

Our tabletop exercise also made clear that the United States would depend heavily on our allies’ preparedness and resilience as much as our own. Countries that planned for and built capacity to deal with the migration, food security, or physical infrastructure threats posed in the scenario were likely to be in a position of strength and valued alliances. The back-casting portion of our exercise illuminated the value of seeking those types of capacity-building preparations in our alliances.

Finally, the tabletop exercise exposed many U.S. limitations when considering the accumulating impacts of climate change. In reality, there is no 2030 scenario per se. Rather, we are already witnessing the steady erosion of the resources and institutions underpinning stability and security, particularly in the Global South. On the one hand, there is likely 1.5 Celsius of warming worth of greenhouse gases already emitted into the atmosphere, meaning many of the environmental impacts are inevitable. On the other, the extent to which these impacts “multiply” the drivers of conflict and insecurity will be determined by each and every policy decision between now and 2030, or 2050, or 2100. The White House and Congress will be key drivers of U.S. climate policy, yet it will be the Department of Defense that has to deal with the consequences of a deteriorating climate.

Looking Ahead

Running tabletop exercises on the consequences of climate change in the Defense Department (beginning with the newly mandated Climate Working Group), other U.S. government departments and agencies, and with allies and partners would be relatively low cost and offer high returns. Doing so would help stakeholders across the government gain immediate insights about where the Defense Department might be underprepared or under-resourced. The most important lesson from the tabletop exercise, based on our experience, would likely be the vast scale and resource challenge that climate instability poses to the Department of Defense mission in the next five to 10 years. We also believe it could help drive an intellectual breakthrough for leaders that takes the threat from the abstract to the imaginable, allowing them to begin to make decisions today to understand risk. A tabletop exercise can help leaders quickly understand what they don’t know about the climate challenge. It can provide insights as to how they may need to transform their own organizations and bring new expertise on board.

While it may seem hard to believe now, in time climate change may be the most formidable and unpredictable adversary the Department of Defense has ever faced. U.S. adversaries typically have motivations that can be scrutinized and resource limitations that can be exploited. Their actions can be deterred. Runaway climate change would be merciless. The planet has no regard for borders or conventions or theaters of war. The changing climate will affect every aspect of life on Earth, and by extension, every facet of America’s strategic operating environment. In some instances, it will amplify existing security risks, while in others it will force the national security apparatus to consider new risks entirely. It will drain resources from military readiness and modernization within Defense Department budgets and as tradeoffs are made to fund other federal priorities in response to climate change.

Protecting the nation’s interests means proactively building a long-term climate action strategy with other branches of government, segments of society, and global partners — a theme ably picked up on by the newly released Interim National Security Strategic Guidance. It means more than hardening assets and bolstering resilience but building strategies to prevail in this new and uncertain future. Like many other entities in both the public and private sectors, the Department of Defense has been thinking about climate change as one item in a long list of global challenges, but not as the dominant global trend that will frame all other issues. The Biden administration’s early charge to make climate change a central priority gives the Department of Defense an opportunity to better understand a future that will create compounding stresses and challenges affecting its future as much if not more than a rising China.



Samuel Brannen leads the Risk and Foresight Group and is a senior fellow in the International Security Program at the Center for Strategic and International Studies in Washington, D.C.

Sarah Ladislaw is senior vice president and director of the Energy Security and Climate Change Program at Center for Strategic and International Studies. 

Lachlan Carey is an associate fellow with the Energy Security and Climate Change Program at Center for Strategic and International Studies.

Image: U.S. Air Force (Photo by Tech. Sgt. Darnell T. Cannady)

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