Climate Change as a National Security Threat and What to Do About It

Naval Station Norfolk_edited

The second volume of the Fourth National Climate Assessment was released by the White House last Friday. Much ink has already been spilled on the significant potential economic impacts of climate change identified in the report, but another significant takeaway has drawn less attention: During this administration, concerns about the national security implications of climate change have grown, rather than decreased. This is consistent with assessments from the U.S. military and the intelligence community over the past two years, and is based on one simple truth: We are already seeing the effects of climate change on national security, and it isn’t pretty. And if not enough is done, it will only get much worse.

Climate and U.S. National Security in Context

The report assesses a range of ways that climate change could impact the United States directly, as well as international implications that could affect the United States indirectly. The study seeks to help decision-makers better identify risks that should be avoided and reduced. Embedded within this congressionally mandated quadrennial assessment from 13 different federal agencies, including the Department of Defense, is an increased attention to the national security risks associated with a changing climate. The security warnings are in part a response to the last National Climate Assessment’s call for increased consideration of these issues, but also a reaction to facts on the ground.

Since the last report in 2014, assessments of climate impacts on national security have become more numerous and more granular, including during this administration. The last two Worldwide Threat Assessments released by Director of National Intelligence Dan Coats identify climate change as a national security threat. At least 19 senior military officials, including Secretary of Defense James Mattis and Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, have spoken publicly about the security implications of climate change since President Donald Trump took office. This was often in response to growing risks to military assets and operations, ranging from the sea level rise threat to Marine Corps training grounds in coastal South Carolina, to a rapidly-expanding Sahel in Africa Command’s area of responsibility. These public statements from serving senior military leaders, in particular, seem to mark an increase in warnings that have persisted across multiple administrations, both Republican and Democrat. You can find a full listing of the U.S. government policy documents that address climate and security issues at our Climate Security Resource Hub.

This new report reflects the perspectives of an increasingly worried national security community. It includes a broad look at climate change impacts across the United States, and a comprehensive assessment of what some of those impacts mean for national security. These include both direct and indirect impacts. Directly, climate change is increasing risks like storm surge, droughts, and wildfires, that can and have already been impacting military and critical infrastructure. Indirectly, climate change acts as a “threat multiplier,” increasing stress on water, food, and energy systems, that can then increase the likelihood of conflict and state fragility, both domestically and internationally.

Have You Ever Seen the Rain?

The new report affirms that the national security implications of climate change are already happening and are likely to become increasingly significant under plausible climate change trajectories, exacerbating impacts both directly on America’ military and critical infrastructure, and indirectly in the global operating environment. This is exacerbated by another important observation in the report: these direct and indirect risks are not likely to occur in isolation — they are increasingly interconnected and happening simultaneously, raising the scale and complexity of these risks, and increasing the danger to U.S. national security writ large.

The report’s findings on the direct impacts of climate change on our national security is all about risks to the critical, hard infrastructure that helps sustain our national strength, and the military personnel who support it. These threats are explored in detail across a range of thematic sections in the 29-chapter report, including those on energy, the coastline, human health, adaption, and in the chapters dedicated to individual regions of the United States .

Chapter four on energy, for example, notes that climate change and extreme weather events are affecting the U.S. energy system and are projected to drive “more frequent and longer-lasting power outages affecting critical energy infrastructure and creating fuel availability and demand imbalances.” The authors state that such events can have “cascading impacts on other critical sectors, potentially affecting the Nation’s economic and national security.” The assessment of coastal effects highlights the Hampton Roads area of southwest Virginia, which former Secretary of Defense Leon Panetta called the “greatest concentration of military might in the world.” It is also one of the regions in the country most vulnerable to climate change. The report also highlights Naval Station Norfolk, a critical military base that sits in a region that is both subject to some of the greatest levels of sea level rise in the country (the station is less than ten feet above sea level), and is sinking due to subsidence. Naval Station Norfolk is home to “multiple aircraft carrier groups and is the duty station for thousands of employees.”

If you’re wondering what health could possibly have to do with national security, the report has that covered as well. As the climate change and health section highlights, an increase in the transboundary transmission of infectious diseases due to regional climatic changes could have a significant impact on the U.S. military, especially on the health of the force. Force health protection is critically important for maintaining U.S military readiness, and this is being challenged by changing and unpredictable disease vectors. One example is the Zika virus, whose spread may have been facilitated by warming conditions that expanded the geographic range of carrier mosquitoes, and by one of the strongest El Niños on record in 2015–2016.

It’s not just threats to U.S. territory itself that pose a risk to U.S. national security. The Asia-Pacific is experiencing climate change in very unambiguous ways, from island nations and territories facing daily flooding and saltwater intrusion, to natural disasters driven by increasingly severe storms. This has major implications for the U.S. military. Former head of what was then called U.S. Pacific Command, Adm. Samuel J. Locklear (full disclosure, he’s now on our advisory board) once noted that while troops serving under his command may not participate in a war-fighting mission during their time with Pacific Command, they would certainly participate in a disaster-relief mission. The report’s chapter on Hawai‘i and U.S.-Affiliated Pacific Islands highlights increased pressures on critical military capabilities, noting: “though the islands are small, they are seats for key military commands, with forces stationed and deployed throughout the region providing strategic defense capabilities to the United States.” For example, under a 3.2-foot sea level rise scenario, the authors assert that “highly impacted areas at risk of large economic losses include the U.S. Pacific Command and military infrastructure concentrated in Pearl Harbor.”

The report’s findings on the indirect impacts of climate change on national security are extensive, and not easily broken down. These involve how climate change is a “threat multiplier” — exacerbating those human security challenges, and potentially driving them to scale up into higher-order security problems like political unrest, conflict and mass migration.

Chapter 11, for example, describes how climate change can contribute to a reduced supply of critical provisioning services (food, fiber, and shelter)” and that this “has clear consequences for the U.S. economy and national security[.]” The chapter titled “Climate Effects on U.S. International Interests” includes the most extensive exploration of climate change’s threat multiplier effect, with a focus on its relationship to conflict. The report claims that while direct causal relationships between climate change and conflict are “unclear,” the “potential for conflict increases where there is a history of civil violence, conflict elsewhere in the region, low GDP or economic growth, economic shocks, weak governance, and lack of access to basic needs.” This is consistent with a 2016 study of global data sets which concluded that climate change already increases the likelihood of conflict in “ethnically fractionalized” countries. If the climate scenarios portrayed in this assessment occur, that likelihood will significantly increase across a wide range of vulnerable regions.

Specifically, the assessment points to the links between climate-exacerbated extreme weather events around the world and political unrest in the Middle East and Africa. A cascading and global series of extreme droughts in 2010, for example, “contributed to a doubling of global wheat prices in 2011 and a tripling of bread prices in Egypt.” The text continues: “This and other factors, including national trade policy and poverty, contributed to the civil unrest that ultimately resulted in the 2011 Egyptian revolution.” The section also includes a reference to Somalia, where drought “has forced herders to sell livestock they could not provide for, reducing their incomes and leading some to join armed groups.”

The report noted that climate change and human migration is “another potential national security issue,” but with the caveat that “whether migration in response to climate change will generally cause or exacerbate violent conflict is still uncertain.” The assessment did not, however, address the question of how climate-exacerbated migration might affect political dynamics in host (or potential host) countries, such as contributing to a rise in ethno-nationalist political forces, and what the security implications of those dynamics might be. A pressing question for the next NCA, perhaps.

Here Comes the Sun?

Lest the reader spiral into despair, the report does include some solutions — both proposed and already underway. In the adaptation chapter, Naval Station Norfolk comes up again. This time, there’s a positive lesson to learn. In response to a rise in sea level and increases in problem flooding, Naval Station Norfolk has “replaced existing piers with double-decker piers that are elevated by several more feet and thus more resilient to rising sea levels and extreme weather events.” These are the kinds of investments that will be increasingly necessary to deal with climate impacts to critical infrastructure, and they’re not going to be cheap.

Chapter 17 also includes some illustrative solutions from the military realm, identifying the Department of Defense’s integrated approach to dealing with climate change risks to its mission. Given its global reach, the assessment reads, the Defense Departmentintegrates consideration for the implications of climate change and variability for food, water, energy, human migration, supply chains, conflict, and disasters into decision-making and operations around the world.” That isn’t just rhetoric, either. That integration has driven the Pentagon to explicitly include climate change factors in its “planning processes” and facilitated public and private partnerships. In the International chapter, the authors highlight a couple examples of that integration into planning, including “a comprehensive scenario-driven examination of climate risks from sea level rise to all of its coastal military sites” and “strategies [by the U.S. Coast Guard and Navy] to respond to the changing geopolitical significance resulting from the projected absence of summer sea ice [in the Arctic] in the next few decades.

That said, the full report implies quite strongly that under a number of plausible warming scenarios, climate change risks to national security could prove difficult to manage and adapt to. In that context, this National Climate Assessment offers another compelling national security rationale for reducing the scale and scope of climate change, and not just adjusting to the inevitable.

Not Just for Tree-Huggers

Ultimately, it’s important to understand that this assessment was not just written by climate scientists. It includes input from 13 different departments and agencies across the U.S. government, including the Department of Defense. These departments and agencies were tasked with conducting an assessment of climate change and its impacts on the nation’s broad array of critical human systems, and not just on the nation’s environment. When it comes to the national security component of that assessment, if we take the judgment of our military seriously when it relates to other national security challenges, such as the proliferation of nuclear weapons and terrorism, why would we ignore their judgment on climate change?

This fourth National Climate Assessment demonstrates that the people and institutions responsible for our national security are increasingly worried about climate change, and increasingly doing something about it. It’s time U.S. political leaders heeded their warnings, and followed their examples.


Caitlin Werrell and Francesco Femia are CEOs of the Council on Strategic Risks and Co-Founders of the Center for Climate and Security, a DC-based think tank with an advisory board of senior national security and defense leaders. They are co-authors of “Did We See It Coming?: State Fragility, Climate Vulnerability, and the Uprisings in Syria and Egypt.”

Image: Aerial view of Naval Station Norfolk, U.S. Navy photo by Mass Communication Specialist 1st Class Christopher B. Stoltz.