In a recent study, geography professor Justin Mankin and Stanford postdoctoral fellow Christopher Callahan found that the emissions of 111 fossil fuel companies have cost the global economy an estimated $28 trillion. The study, which was published on April 23 in the journal “Nature,” uses emissions data from 1991 to 2020 to model the Earth’s climate with and without the pollution of major companies. The Dartmouth sat down with Callahan and Mankin to discuss the findings of their research, the study’s framework and the future of climate policy.
What prompted you to look into the cost of fossil fuel companies’ emissions?
CC: This has partly been motivated by these legal cases and “polluters pay” bills that have been emerging both in the United States and around the world. There is an emerging push for emitters to pay the costs of their emissions, and so one of the goals for the study was to evaluate the scientific support for that idea.
Your study covers the period 1991 to 2020. How did you determine this time frame? What challenges did you encounter in attributing long term economic impacts to specific emission sources?
CC: This is in many ways a data issue. We wanted to assess the global economic implications of extreme heat, and we were able to put together income data around the world for that period, starting in the early 1990s to the present. It would have been a significant challenge to extend that back further in time, because our data on local economic output is not that good the farther back you go in time.
JM: We think of climate science as kind of representative of this era of big data, but there are a lot of places where we are lacking data that we require in order to track the impacts of climate change, or the magnitude and pace of climate change itself.
What was the most challenging part of your study?
CC: It’s not only data gaps in general, but it’s data gaps precisely in the places where we think impacts are most severe. We had to do some work to overcome that by actually putting together a new data set of long-term economic growth.
JM: There were analytical challenges, to be sure, but I think a lot of the challenges around this paper were getting a handle on where the legal and policy landscapes were. And then the limits of science to be meaningful in that context.
How do you think your findings could be used to hold fossil fuel companies accountable for their emissions? How realistic is it that these companies would successfully be sued on this matter?
JM: There are some scales at which accountability is being pursued. Do I think that liability cases and that holding polluters accountable is going to be the means by which we transition our global economy away from fossil fuels, or that we actually recoup that which we’ve already lost? I can’t really imagine a world where that’s the case.
I can imagine that this science is going to be essential to informing the implementation of the superfund laws and the legal challenges that they sustain. I can imagine that this is going to be essential for liability cases going forward. But I think this broader question of, what is a true societal reckoning with the harms wrought from emissions? That’s the province of civil society.
Have you encountered any resistance or interests from policy makers so far? How are you planning to navigate attempts to possibly undermine your findings?
CC: The primary pushback, it’s more about the conceptual framework. In our approach, if you’re driving a car, buy gasoline and burn that gasoline that was produced by ExxonMobil, we link those emissions back to ExxonMobil. But it might be equally reasonable to say that those emissions should belong to you and not to the producer. On the other hand, given that these producers knew about the harms of climate change and actively engaged in campaigns of disinformation and delay to prevent climate action, I don’t think it’s that unreasonable to locate responsibility with them.
JM: Even though this was a tailored analysis for a particular set of liability questions, I think it actually is really important to the broader accountability conversation, because it removes any ambiguity about the potential to draw very specific causation, which before had plagued attribution science.
This interview has been edited for clarity and length.
