The ongoing United Nations Environmental Assembly meeting in Nairobi, Kenya, has revealed sharp splits among countries over the risks of geoengineering projects. Energy from renewable sources is set to increase rapidly, putting downward pressure on energy prices and affecting major producers. Anger is growing within the developing world over climate change and what they see as the grossly inadequate response of wealthy countries that account for the majority of the causes of climate change. The early signs of how climate change is driving widespread shifts in the international system are clearly visible.

Yet in U.S. policy discussions, attention to the national security implications of climate change remains incomplete. Over the past three years, the U.S. government, and the Department of Defense (DoD) in particular, have developed strategies and assessments regarding the national security risks of climate change and how to adapt to them. These documents have been informed by substantial research in the broader U.S. policy community on issues such as the threats to military installations and operations from extreme weather events, and to a lesser extent the potential for shifts in climate to drive migration or resource conflicts. These topics are certainly important, but they are primarily examples of research into direct reactions to extreme weather events. There have been some thoughtful assessments of the broader risks to U.S. national security from climate change, but implications from this work do not yet seem to be driving government policy.

This is concerning, because the risks from direct reactions to extreme weather events may be only the tip of the (rapidly-melting) iceberg. As we argue in our newly-released report, climate change has at least two characteristics that are likely to drive second- and third-order political and social reactions whose effects on U.S. strategic interests may be substantially greater than those that occur in direct reaction to individual extreme weather events.

First, because climate change is set to produce a durable, long-term shift in the environment, it is likely to drive States and societies to take increasingly strong steps to mitigate and adapt to it. In earlier eras, a bad hurricane season would not prompt serious interest in the possibility of dimming the sun, but the threat of sustained increases in the frequency and severity of extreme weather events is driving those conversations now. As the effects of climate change accelerate in the years to come, we will need to revisit our assumptions about the types of actions states may be willing to take in response, particularly as the risks that climate change poses for many states will be existential.

Second, the fact that climate change – unlike historical storms, droughts, or floods – is caused by human activity, and by the activity of some humans quite a bit more than others, has the potential to generate more explosive political and social reactions as the costs it imposes on some, but not others, escalate. That is, unlike with historical natural disasters, climate change-driven disasters come with someone to blame. The United States is the largest single historical contributor to carbon dioxide emissions, at roughly 25 percent of the historic global total. While China has surpassed the United States as the largest annual emitter of carbon dioxide, the United States remains one of the current world leaders in emissions.

The fact that climate change can be attributed to specific actors is likely to charge reactions to it with a political and emotional salience that has been lacking in prior responses to natural disasters. Anger, resentment, and frustration towards major polluting nations or corporations may affect geopolitical alignments, remaking alliances around climate considerations in addition to traditional security threats, or drive societal-level reactions such as boycotts and divestments of companies associated with emissions. It may even spur increased ecoterrorism.

The extent of these risks and their implications for U.S. national security remains uncertain. In part, this is because the success of international efforts to reduce greenhouse gas emissions, which would in turn reduce the extent of climate change, is also unclear. But the degree of risk posed to U.S. national security by these changes has also been understudied, likely obscuring the risks that may accompany policy decisions on both climate and non-climate related issues today.

The areas where further research is needed are wide-ranging. Some allies and partners that are considered vital for U.S. basing and access in the Indo-Pacific in particular might be disproportionately likely to be negatively affected by climate change, and, as a result, the politics regarding partnering with the United States or appearing to oppose China might shift. Long-term plans for deterring PRC aggression may not reflect how Chinese development of alternative energy sources could reduce the effectiveness of some tools of statecraft, such as blockades, that could be used to deter armed aggression. Adaptation needs will vary, which may drive apart countries in multilateral institutions, such as the European Union, as they face very different investment needs for adaptation in the future.

In short, climate change may cause additional and more fundamental changes to the future strategic environment that may, in turn, require more fundamental shifts in U.S. policy to address. To better understand these and many other potential changes and how they should inform U.S. policy choices, it will be important to both widen the scope of issues under investigation and deepen the attention paid to them.

IMAGE: Snow geese fly near Controlled Thermal Resources’ Hell’s Kitchen lithium and renewable power plant, the first of several to be built despite the threat of a lawsuit to stall or stop it on February 15, 2024 near Niland, California. (Photo by David McNew/Getty Images)