We are virtually certain that climate change is a human-induced phenomenon, and, more specifically the product of GHG emissions-generating activities. We also know that those who suffer climate change-related harms or are most vulnerable are the least responsible for this phenomenon. There is a wide-spread agreement that these two facts constitute a moral asymmetry.

Some philosophers seek to develop principles of climate justice that integrate this asymmetry in our normative framework. The most straightforward one is the well-known Polluter Pays Principle (PPP). This principle states that polluters should bear the burdens of repairing the negative effects of their emissions, that is, the harm caused to others. This is akin to the principle underlying climate litigation for losses and damages. An example of this is the popular Lluiya case, where a Peruvian farmer has claimed compensation to the German energy company RWE for the protective measures he has implemented to protect his community in Peru’s northern Ancash region.

However, such a principle faces multiple challenges that need to be overcome if we were to implement it in our climate justice normative framework. In this short piece, I address one of those challenges, namely, the attribution questions. Moreover, I show some of the ways in which our normative framework could incorporate scientific developments to operationalize such a principle.

The attribution question concerns the causal link between climate change as a general phenomenon and the specific manifestations of climate change. Although we know that climate change as a general phenomenon has been caused by GHG emissions, we do not know whether a particular extreme weather event (EWE) – such as a storm, extreme rainfall, a heatwave, etc.— has been caused by the accumulation of GHG emissions. We don’t know this because even in the absence of climate change, extreme weather events could result of natural variability.  That is, those events could have occurred for other forces than anthropogenic ones.

In the last decades, scientists have been trying to answer the attribution question. They have used, at least, two different methodologies: the risk-based approach and the storyline approach. The risk-based approach can deliver results about changes in probabilities and magnitude of EWE due to the effects of GHG emissions.  That is, it can deliver results such as ‘climate change has increased the risk of this type of heatwave happening by 60%’. The story-line approach poses a different question. This methodology takes the dynamical factors of an EWE (wind speed, precipitation, etc.) as a given and asks how much climate change has contributed to the increase in the magnitude of the event. Thus, the type of answers provided by the story-line approach are of this sort: ‘climate change has made this storm two times more severe than it would have been otherwise’. As we can see, the two approaches differ in the type of research questions they pose and the answers they provide. Whereas one approach asks about the increases in the likelihood of the occurrence of an EWE, the other one takes certain features of the event as given and asks about the increases in the magnitude of the event.

The story-line approach emerged as a reaction to the uncertainties present in climate models concerning the dynamically-driven climate variables of an EWE. Proponents of this approach believe that those uncertainties do not allow us to rely on the results provided by the risk-based approach. This is the reason why they propose an alternative methodology that take the dynamical factors as a given. Proponents of the risk-based approach may complain that the story-line approach does not ask the kind of questions required in liability contexts and, thus, can hardly provide the answers required for settling justice-related questions. For in liability context, we seek to establish whether a certain event has been caused (probabilistically or otherwise) by another, and we usually do not make conditional assumptions, such as the ones made in the story-line approach.

As normative theorists, we need to decide whether the science of attribution is in a well-developed state already to provide the kind of answer we need to establish a normative significant connection between EWE and GHG emissions. If we believe so, then the next question is which approach can provide better insights for liability contexts. From a legal perspective, whether the science of attribution is developed enough or not may depend upon the requirements of our legal systems to prove causation. If attribution studies cannot provide the kind of answers required in our legal systems as proves of causation, then the answer is no. Whether there is a plausible interpretation of the legal texts that may accommodate the statements provided by the science is something open for legal debate.

From a philosophical perspective, things might be a bit easier, for we can turn the question around. That is, we may have reasons to believe that basing our normative systems in the kind of moral asymmetry that I pointed out at the beginning is relevant for the system to be just. Then, the question is not whether the science of attribution is well-enough developed to provide significant proofs of causation. Rather, the question is what is the best way of making sense of that causation and incorporate it into our policy systems. That is, we first decide (according to moral reasons) that causation is relevant, and then we seek to find out the most accurate way of establishing that causation and use it for the purposes of settling justice questions. Here, I will operate with a conditional statement. Imagine that we believe, as some do, that our policy framework should be responsive to the anthropogenic origins of climate change-related damages because that is important for the moral standing of victims.  The question is which is the best methodology for doing that.

I believe that the debate between the risk-based and the story-line approach needs to be presented in a less confrontative way. It may well be that both approaches are adequate for different purposes, and that they can operate together as best or second-best ways of providing causation in different contexts. I agree with the proponents of the risk-based that their methodology is better suited for liability contexts, for in those contexts we want a ‘yes or no’ answer to the question about whether someone is responsible for an event.  We do not make assumptions on certain elements of the situation to, then, establish certain conditional connections. However, this has the problem that, in events driven mostly by dynamical aspects of climate change, we cannot be sufficiently certain about the results, as changes in parameters within climate models can deliver very different results. This might, indeed, be a reason to switch to the story-line approach when the results of the risk-based approach are not reliable enough.

Notice that this switch is justified even if we do not believe that the story-line approach is pressing the kind of questions that we take as relevant in liability contexts. For all what we want is the best possible approximation to the role of GHG emissions on the negative effects that people suffer as a consequence of climate change. This is probably the most important thing to bear in mind when making use of scientific findings for climate justice-related purposes: many decisions are based on epistemic approximations to the truth about the real effects of climate change, but they might be nonetheless justified if we consider them against the background of the virtual certainty we have regarding the anthropogenic origins of climate change as a general phenomenon.