Published September 05, 2017 by Tom Porter

Could War Ever Be Justified to Fight Climate Change?

Jonathan Atticus Carnell ’18 has spent much of the summer tackling an interesting ethical question: Could a group of people ever be justified in going to war against another group of people to defend itself or another group of people from the effects of climate change?
Jonathan Atticus Carnell ’18
Jonathan Atticus Carnell ’18

Carnell is writing a 10,000-word thesis on the topic, thanks to a Hughes Family Summer Research Fellowship in Environmental Studies. As well as environmental issues, his research delves into ethics, in particular “just war theory.”

“Suppose a small developing nation is very seriously threatened by the effects of climate change, in particular by the actions of large developed nations and the corporations therein. This nation has tried using diplomacy to get these developed nations to curb their emissions and to help them adapt to climate change, but the developed nations continue on as usual, indifferent to the smaller nation’s plight. In this case, would the small nation have a ‘just cause’ to go to war to force any of the developed nations to stop emitting and to help it adapt?”

It’s a question likely to be of increasing relevance to nations like The Maldives and Micronesia, for whom climate change and sea level rise represent an existential threat, and also to countries like Bangladesh, where large portions of land could disappear underwater.

St. Thomas Aquinas
St. Thomas Aquinas

Just War Theory—Old and New

The concept of a ‘just war’ is as old as war itself, but perhaps the most influential exponent from the western Christian perspective was the thirteenth-century philosopher Saint Thomas Aquinas. He laid out a number of conditions under which war could be justified: it had to be a last resort, and for a good purpose rather than self-gain. War must also be declared by a proper authority, such as a state.

Aquinas’s ideas have formed the basis for later ideas. In his paper, Carnell relies heavily on the work of contemporary theorist Jeff McMahan, who has been on the forefront of many recent shifts in just war theory. “Traditionally, aggression—specifically a violation of borders or sovereignty—by one state against another was the only just cause for war. McMahan argues that more than aggression can be just cause for war. Any severe-enough violation of one group of people’s rights by another can constitute a just cause. If this is the case, things get a lot trickier.”

In particular, said Carnell, there is a convenient relationship between those who pose a threat and those who fight a war, that seems to break down when using this model. “When military aggression is the threat that justifies war, soldiers pose the threat and are usually morally responsible for doing so—this is why they can permissibly be targets of violence in war. When some other, nonmilitary threat justifies war, others are morally responsible. Does this mean that those who are morally responsible for climate change can be targeted? And who, anyway, is actually morally responsible for the threat of climate change?”


Carnell is adamant that, despite these complexities, rectifying or preventing the harms of climate change can in theory be a just cause for war. “Nations are formed to protect their citizens,” he stressed, “and this includes against externally originating environmental threats.”

While there may be a just cause for war in Carnell’s mind, this does not mean it should happen. “To be clear, I’m not advocating military action, largely because I don’t think it would succeed—remember, a war must have a ‘reasonable chance of success’ to be morally permissible under just war theory. It ought to be with a sigh when we acknowledge that small, poor nations might not be permitted to go to war, despite their having just cause to do so, simply because they could not succeed against the large, affluent nations that do them harm.”

Climate War

Another factor at play is a deeply personal one for Carnell: “I’m actually a Quaker, so I generally find pacifism morally compelling. But, unlike most Quakers, I do think there are some instances when violence is morally permitted, even required.

“Obviously, it is preferable for people in the developed world to do what they are morally required to do: stop contributing to grave harms to others by curbing personal emissions, support alternative energy initiatives, and so on. But, when we fail to do these things, we violate the rights of others.” Carnell said a quote from Simon Caney, a political theorist at Oxford University, sums up his motivations for writing this paper: “… in debates surrounding global justice… the emphasis has been on [the duties of the affluent and powerful] to comply with the principles of justice,” * but not on how the victims of injustice are permitted to respond when the affluent and powerful do not. “I hope my paper helps combat this trend,” said Carnell.

* Caney, Simon. “Responding to Global Injustice: On the Right of Resistance.” Social Philosophy and Policy​ 32 (1): 51 (2015)