Thanks to some comments by Bernie Sanders in the last Democratic debate, the question of whether climate change is a national security threat has once again bubbled to the surface. One day, perhaps, US politics will host an informed and intelligent discussion of this issue. But it hasn't happened yet. Instead, we're asking, "Which is worse, climate change or terrorism?" Oy.
I highly recommend Brad Plumer's lucid explainer, but I think it's helpful to pull back a bit from the empirical questions and focus on clearing the conceptual underbrush, as it were. This is one of many discussions around climate change that strikes me as a fight over meaning masquerading as a debate over facts.
We're trying to figure out how to think about, and talk about, climate change, and most of our familiar mental and linguistic categories fall short; they distort some aspects of climate change even as they illuminate others. It's a bumpy process, unpretty, but it could not be more important. How we think about climate change will help determine how we address it.
So let's take a few steps back and think about what we mean when we call climate change a national security threat.
We approach climate change through metaphors
Let's start with a metaphor. Or rather, a word about metaphors and then a metaphor.
As a phenomenon, climate change is so enormous, complex, and far-reaching that it's very difficult to grasp directly. We ease that cognitive work with metaphors, which liken climate change to other, more familiar phenomena. And climate change has been clothed in many metaphors: It's a pollution problem, an economic opportunity, a global hoax, a UN scheme, a spiritual crisis, a moral/religious call to arms, a national security threat.
None of them entirely fit. Climate change reminds me of Mr. Snuffleupagus, the old Sesame Street character who could never quite pass as anything but his idiosyncratic self. (Though the other characters on the show finally acknowledged Snuffy in 1985, so I guess he's a step ahead of climate.)
The national security metaphor is just as ill-fitting as the others in many ways. Global warming is unlike other things we think of as national security threats in important ways. It has no face, invades no territories, directly hurts no one. Yet in the aggregate, it degrades US security and threatens to degrade it much more. We just don't have great ways of talking about stuff like that.
So here's my attempt at a metaphor.
Say there's an evil scientist, and from the safety of his satellite fortress, he figures out how to crank up gravity on Earth by 1 percent.
It might take people a while to even notice. Everything would weigh ever so slightly more, but still the same relative to everything else. People would feel basically the same. Yet globally, on average, the number of people tripping and falling would rise relative to baseline. Maybe just by a little bit. But the effect would definitely register.
Now you're jogging along during your first week in this new world. A bike cuts a little close to you, you try to hop a curb, your foot catches, and you fall.
Did the evil scientist cause you to fall? Well, not really. There was the bike; you were distracted; your muscles weren't limbered up; there was uneven pavement, wind. These "proximate causes" are all far more salient to an explanation of your fall than anything the evil scientist did.
How much of a role, if any, did the change in gravity play? It's impossible to know that for certain, but we can make an educated guess. The question is whether the proximate causes were sufficient — whether falling was a typical response to those conditions — or whether it was unusual to fall in those conditions, indicating that some further explanatory variable is needed.
This is a highly approximate business, though; if you look closely enough, any incident of tripping and falling is almost infinitely complex. (Think of all the neural activity.) Picking out the background signal of extra gravity from all the more proximate noise is extremely difficult. It's rarely possible to untangle all the causal chains in an entirely satisfactory way.
And yet! If gravity rose by 1 percent and then the global number of tripping-and-falling incidents rose, it would be peculiar not to conclude that the change in gravity was responsible in some way.
How do we talk about that responsibility? Does the extra gravity cause people to fall? That doesn't seem quite right. Does it cause the increase in people falling? That seems a little better. Or maybe you don't like "cause" at all, and you'd say extra gravity "leads to" more falling or "increases the probability" of falling.
It's helpful to hash that out, but it's also important to remember that it's not really a disagreement about the underlying facts: Gravity went up; tripping went up; the latter happened because of the former. The disagreement is about how to capture those facts in everyday language, which is inevitably freighted with moral and political implications. (Is the evil scientist culpable for anything in particular? Can he be convicted of a crime?)
The carbon causal chain is long and tangled
So in case the belabored metaphor is not clear, the increase in atmospheric greenhouse gases is the 1 percent gravity boost in this situation.
And here, a quick terminological nitpick: Climate change doesn't technically cause anything. Climate change is an effect, namely a set of changes in climate caused by increased greenhouse gas concentrations in the atmosphere. Greenhouse gases are the causal agents here. Or, if you prefer, human beings are.
Here's the chain: We dig carbon out of the ground, burn it, and release carbon dioxide. It accumulates in the atmosphere, trapping more heat energy close to the planet's surface. That energy increases global average temperature but also has a host of more specific effects on various biophysical systems, differing region to region.
In many places, those biophysical changes will increase the probability of disruptions in socioeconomic systems. Seas will rise. Agriculture will suffer. Storms will grow harsher. Inter- and intranational migrations will become more common. Hunger, dislocation, and ideology will mix and lead to violence in some places, simple suffering in others. In the aggregate, there will be more instability; US resources, military and otherwise, will be called upon more often.
That's the causal chain from carbon combustion to national security threats. As you can see, it is extremely long and tenuous. In some ways, the climate science is the easiest part to figure out. We can get a decent sense of whether a drought is unusually hot or long relative to historical records. But trying to untangle the causes of a particular episode of human violence is devilishly difficult. Would events in Syria have unfolded differently if the recent droughts there had been, say, 15 percent less severe? We have no idea.
Much like we can never definitively say exactly what role the rise in gravity played in your jogging accident, we cannot definitively isolate the role of increased atmospheric carbon dioxide in the unrest in Syria.
Nonetheless! We can say that rising atmospheric GHGs have made situations such as Syria more likely at the margins, and that they will send an increasingly clear signal in the future. We can say that, in aggregate, there will be more such situations in coming decades. We are collectively cranking up gravity and can expect to trip and fall more.
(Incidentally: The reasoning above is true about anything allegedly "caused" by climate change — not just social unrest but, say, individual storms, droughts, or fires. In all such cases, the causal chain is long and indirect, but salient nonetheless.)
What the national security metaphor does and doesn't mean for strategy
If we think of climate change as a national security threat, we are then confronted with the question of how to reduce that threat. And this is where we must be careful not to let our metaphors mislead us.
The very strong implication of "climate change increases terrorism" is that mitigating climate change, by reducing greenhouse gas emissions, will reduce terrorism.
And it might. But not in our lifetimes.
Climate change works on longer time scales than humans are accustomed to. The carbon we emit today has an incremental effect on the temperature in three to five decades. Similarly, carbon we don't emit today will avoid some incremental effect on the atmosphere (and thus some incremental boost to the chances of violence) in three to five decades.
Neither — emitting or avoiding carbon — will have any material effect on national security threats as they exist today or in the next several decades. That's just physics. Whatever climate phenomena might shape those threats are already "baked into the cake" by previous emissions.
Greens are going to yell at me for this, so I want to be very clear: We absolutely should reduce carbon emissions, for a million reasons. One of those reasons is that reducing emissions today will make our children and grandchildren more secure (or rather, less insecure, relative to baseline) than they otherwise would have been.
But greens should not claim, or be seen to claim, that mitigation efforts are going to materially affect the fortunes of, for example, ISIS within the careers of today's policymakers or military officials or the political horizons of an impatient public. The causal chain is just too diffuse and temporally extended for that. As a national security strategy to counter terrorism, carbon mitigation is a terribly inefficient.
Insofar as climate change is accelerating today's national security threats, the proper response by the military is adaptation, or, to use a more familiar word, preparation. The disruptions and dislocations of the next 30 to 50 years must be accounted for in planning and spending — that's what the Pentagon means when it stresses the climate-security connection. The national security community takes that obligation very seriously, as the long, bipartisan list of signees to this statement makes clear.
Mitigation and preparation are both important. But for the purposes of military planning, it is primarily the latter that will matter.
How to think clearly about climate and security
Carbon pollution is a driver that accelerates instability and the social dysfunctions that come along with it. It is only one driver among many, and today, in the early stages of climate change, its effect is generally marginal compared with more immediate demographic, economic, and social forces.
Nonetheless, the impacts of increased atmospheric greenhouse gases are already detectable around the globe, and we know from scientific research that they are only going to get worse. Eventually the carbon signal will get louder and stand out more clearly. That's going to happen no matter what we do; we're living with the emissions of our forebears.
A more unstable globe is a threat to US national security. But it is utterly daft to compare climate change (background) and terrorism (foreground) and ask which is "worse." It would be like asking which is the worse threat, extra gravity or tripping. It's a category mistake; they are not separate. The threat of climate change expresses itself through terrorism, through hunger and migration, through faltering and failed states.
The threat will grow no matter how fast civil society reduces emissions (though emission reductions can ensure it grows less than it otherwise would). So the military must prepare. The Pentagon gets this; it's the rest of the political class having trouble with it.
We're just not used to thinking in terms of responsibility for conditions that lie that far in the background. We're not used to the Anthropocene, an era in which the very global preconditions of human existence are starting to shift in response to human behavior. That's is why conservatives like Jeb Bush call it "arrogant" to think humans shape the climate. It is a degree of power, of agency, that is terrifying to contemplate — especially if you know some humans.
Nonetheless, He no longer has the whole world in His hands. We do. In one sense, greenhouse gases sit awkwardly beside the other things we think of as national security threats. But in another sense, of course they are a national security threat — they are a threat to all of humanity, of which the US, despite its occasional pretensions, is still a part.