My piece on how libertarians should think about liability for damages from climate change has drawn a thoughtful response from Jordan McGillis at The Institute for Energy Research (IER). McGillis agrees with me that to frame issues involving pollution in terms of property rights is a valid approach, but raises several objections to this approach as a basis for making businesses liable for global warming.

I want to address each of those objections in turn, but before I do I need to clear up a possible area of confusion. In my previous post, I laid out two different libertarian responses to property rights violations caused by pollution. The first, represented by Milton Friedman, says that the proper response when third parties are harmed by pollution is to impose a tax that makes the pollution bear the cost of the harm. This approach has been the basis for R Street’s own longstanding support for a revenue neutral carbon tax.

The second approach, represented by Murray Rothbard, takes a harder line. Rothbard would not have supported a carbon tax because doing so would allow emitters to continue to harm property holders as long as they paid the tax. Instead, Rothbard favored an absolute ban on harmful pollution, enforced by the courts.

Now Rothbard does require a plaintiff to prove that they have or will be harmed by the emissions they are trying to get enjoined. It is reasonable to question whether a plaintiff would be able to do that in the case of climate change. It is also an important question, since under a Rothbardian system, a plaintiff who can prove harm from greenhouse gas emission caused global warming could have the great majority of emissions shut down, irrespective of the costs this would impose on business or on society as a whole.

McGillis argues that a plaintiff would not be able to meet their burden of proof in the case of climate change, for several reasons. First, McGillis argues that “[w]hereas a compound emitted by the factory of A, like sulfur dioxide, can infiltrate the property and person of B and adversely affect his respiratory function, greenhouse gasses (within the range of real-world emissions) cause no such direct harm.”

It is true that the harms caused by greenhouse gas emissions are indirect. For example, a person harmed by climate change is not harmed because he gets sick from breathing carbon dioxide. Instead, he might be harmed because carbon dioxide emissions trap more heat in the atmosphere, raising temperatures, which causes melting icecaps, which leads to his house being flooded. In many cases the causal connection between the emissions and the damage to property may be even more complicated. But does the fact that the harms are caused indirectly mean that there can be no liability? No. Suppose I am setting off dynamite on my property (as one does) and the shock wave from the blast sets off an avalanche that destroys your house. Can I escape liability on the grounds that it was not the explosion itself but the avalanche triggered by the explosion that caused the damage? Certainly not.

Second, McGillis says that a plaintiff cannot succeed in a climate liability case because he cannot prove that the damage to his property was caused by greenhouse gas emissions, rather than natural factors:

As Rothbard writes, “a strict causal connection must exist between an aggressor and a victim, and this connection must be provable beyond a reasonable doubt. It must be causality in the commonsense concept of strict proof of the ‘A hit B’ variety, not mere probability or statistical correlation.”

Claims of climate-related damage lack, and will continue to lack, such particularity. Even accepting [Intergovernmental Panel on Climate Change] climate projections, it is not possible to attribute particular phenomena, such as a river flooding and detrimentally inundating cropland, to climate change as opposed to meteorological variability.

It is true that it is not always possible to prove strict causality in cases of harm. For example, suppose I leave some radioactive waste piled up in my backyard, and the resulting radiation exposure doubles the odds of my neighbor developing thyroid cancer. Even if my neighbor does later develop thyroid cancer, it will be unclear whether this was due to my actions or to natural causes. Many instances of climate-related damage will be like this in that it will be impossible to tell whether they are the result of human or natural causes.

However, there are experts who are willing to attribute specific events to human-caused climate change, and for some of the future projections (like Miami ending up underwater) the cause and effect link would be even stronger. Whether causality can be proven in a specific case is not a matter of libertarian principle; it is a factual question that would have to be decided by the courts. Additionally, I would add that if libertarian theory allowed for potentially trillions of dollars in damages to be inflicted on property owners without recourse, that would seem to be a large blind spot for the theory.

McGillis also argues that trying to enjoin emissions from particular sources would be futile because there are simply too many emitters to make a difference: “The U.S. already contributes less than 15 percent of annual global emissions—and that figure will continue to decline. As a result, even if we take the alleged domestic harms of climate change as given, the question of redress is still left unanswered.”

It is true that stopping emissions from a single emitter, or even a single country, will not stop all or even most of the damage from global warming. It does not follow, however, that because many different people are violating my property rights I cannot stop any of them from doing so. Suppose that you and my neighbor, enraged by my actions in the prior hypothetical examples, both independently slip poison into my coffee, sending me to the hospital. When brought before the court, you make the ingenious argument that since I would have been hospitalized even if you had not poisoned my coffee, you cannot be held liable. My neighbor, of course, then makes the same argument for why he cannot be held liable. Will the court buy into this line of thinking? Should it? I certainly hope not.

Finally, McGillis asks why, if what I am saying about Rothbard is right, there are not any actual living, breathing Rothbardian libertarians advocating for litigation against greenhouse gas emitters? To this I have two responses. First, as far as I know this is not an issue that many Rothbardians have considered, but where they have, they have at least conditionally suggested that the approach I ascribe to Rothbard is correct. Take, for example, McGillis’ colleague at IER, Bob Murphy. When asked about the proper libertarian response to climate change (assuming it really was a problem), Murphy responded as follows:

Ultimately the solution would be to have property rights in the integrity of the atmosphere and that you’re not allowed as a business – just as you can’t dump chemicals in the river – you’re not allowed to emit tons of CO2 into the atmosphere if that really is causing physical demonstrable harm to everyone else on the planet. So that would be a property rights violation… And people who were being harmed could go to a libertarian judge and say ‘hey that power plant is emitting all sorts of CO2 and here’s the science and see they’re directly causing us property damage.’ And so then they could get an injunction or they could have some kind of agreement where they work out with the owner some kind of compensation scheme.

I do not know if Murphy would actually favor court injunctions against greenhouse gas emitters based on their violation of property rights or–– if he did not–– the reason why. Which leads me to my second response. It is not uncommon for people to fail to advocate what is implied by their principles, not because of hypocrisy, but because the world is a complicated place. Rothbard himself only became an anarcho-capitalist when it was pointed out to him by liberals that this was required by his principles. If I am right that Rothbardian principles require taking a strict line against greenhouse gas emissions and Rothbardians do not do this, then that is a problem for them, not for me.

In closing, I would like to thank McGillis for engaging me on this issue, and would also like to thank the three readers who actually made it to the end (hi Mom!).