In the absence of an enforceable set of commitments to reduce greenhouse gas emissions, concerned citizens may want to supplement international agreements on climate change. We suggest that litigation could have an important role to play.
Many avenues exist for bringing behaviour that drives climate change before the courts. Options include the exploration of fiduciary duties of company officers and directors, as well as those of pension fund trustees. Cases that seek to block state aid to carbon-intensive projects and cases to reform energy markets are also anticipated. The holy grail of climate-related litigation, however, is a determination of liability that some entity, such as an energy corporation or a coal power plant, is responsible to a claimant for climate change damage.
This theory of action falls into the area of tort law, which is concerned with providing remedies for provable harms. Success in such an action revolves around proving causality between someone's actions or negligence and a given damage. These cases will therefore depend in large part on the science that demonstrates this causality. We argue that, if science and the law join forces, there is a good chance of achieving court orders for the restriction of greenhouse gas emissions in the not-too-distant future.
Two aspects of causation
A claimant in such a case of damage from climate change will have to convince the court of two distinct aspects of causation.
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The second aspect of causation that the court will have to accept is more complicated to prove. The claimant needs to convince the court that anthropogenic emissions are the cause of the particular climate event that the claimant alleges to have caused a specific harm.
To understand the challenges of winning such a case, consider two hypothetical cases that are simple to claim but difficult to prove. In the first case, a woman claims that her mother's death was caused by an extreme heatwave in Australia, which in turn was caused by climate change. In the second case, a man claims property damage from a storm surge along the coast of Devon.
Assume we can get past the first causation hurdle: that an English or Australian court would agree with the Urgenda ruling that anthropogenic emissions of greenhouse gases into the atmosphere cause, or at least contribute to, climate change.
Then we have to identify a defendant. Say it is a coal burning utility. Its emissions, according to our assumption above, contribute to climate change. Under tort law, the crucial question then is whether the utility has a duty of care to the claimant. This duty of care depends on what a reasonable person would have thought in the position of the defendant. We would need to decide at what point in time the knowledge that they were contributing to climate change and its damages should be imputed to the utility. Assume that we can convince the court that 2007, the date of the first IPCC report that found a 90%-or-higher confidence level for human-induced warming, is the point in time at which a reasonable person should have known.
The second aspect of causation evaluates whether this defendant caused this harm to this claimant. In the case of climate change, a defendant or group of defendants contributed to the harm in a way that can potentially be quantified with reasonable certainty; however, they were not the only contributors.
Epidemiology analogues
To have a clear example of how a court might approach this issue, let us look at the English courts. We will examine the closest useful parallel to climate change provided by the jurisprudence of this court system: how epidemiological evidence has been used in health cases. In these cases there is a clear harm, but difficulty in showing that the harm was caused by a specific defendant.
Let us start with a relatively simple case from the point of view of damage attribution. In XYZ versus Schering Health Care, the claimants argued that oral contraceptives that they had been prescribed caused them to suffer from deep vein thrombosis. The trial court considered extensive epidemiological evidence. Though it was troubled by the conflicts in the testimony, the court came to a numerical conclusion on risk. It decided that the contraceptives in question increased the risk by 1.7 times. The court determined that this was not enough for the claimants to win. An increase in risk of at least two times would, however, have been enough.
Simply stated, the English courts appear comfortable holding a defendant liable in health cases if the defendant's products or actions have more than doubled the risk of a medical condition.
A more complicated case, with multiple potential defendants whose individual contributions are uncertain, involves asbestos. Malignant mesothelioma is caused by asbestos fibres. In Fairchild versus Glenhaven Funeral Services Ltd, the House of Lords carved out an exception to the 'risk-doubling' rule. Malignant mesothelioma is not dose-related, and may be caused by a single fibre of asbestos lodging in the lung. A claimant may have worked for multiple companies who exposed him but will never be able to prove where he inhaled the deadly fibre. The Court therefore decided to hold the employers joint and severally liable and allow apportionment of the damages among them.
In a more recent UK Supreme Court case, Lord Mance's observations on epidemiological evidence indicate a generally cautious approach: “That epidemiological evidence used with proper caution, can be admissible and relevant in conjunction with specific evidence related to the individual circumstances and parties is, however, common ground and clearly right... Whether, and if so when, epidemiological evidence can by itself prove a case is a question best considered not in the abstract but in a particular case, when and if that question arises. If it can, I would hope and expect that this would only occur in the rarest of cases.”
In the latest Supreme Court case looking at epidemiological evidence, the Court decided not to extend the Fairchild exception to the risk-doubling rule beyond mesothelioma cases. In Ministry of Defence versus AB and others, the Court reviewed claims by men who had served in the British Armed Forces, and who argued that exposure to fallout from nuclear testing had increased the risk of illnesses they suffered. The claimants argued that the radiation materially increased the risk of their diseases, but the Court declined to extend the Fairchild exemption to their medical conditions.
The case for climate litigation
With those waymarks of the English courts' views on statistical evidence to guide us, let us look at what the science of climate attribution can say about causation.
Storm surges and heatwaves are the events that the science is most comfortable in attributing to anthropogenic change. The interesting point from the forensic perspective is how surprisingly the odds have shifted in recent years.
For example, the record-breaking seasonal temperatures seen during the 2003 and 2012 heatwaves in Europe would have been at least a 1 in 1,000 years event in background climate conditions without anthropogenic greenhouse gas emissions, but are now about a 1 in 5 years event. However, is this huge statistical shift enough to convince a court?
In the heatwave case, the risk of the event that gives rise to the harm far more than doubled, an increase in risk that the court was comfortable with in the contraceptives case. However, in the latter there was a single defendant responsible for the harm. Even though the total probability for a heatwave has much more than doubled with climate change, it is a large group of actors who are responsible. None of them individually has come close to doubling the risk.
The multiple contributors to the increase in atmospheric greenhouse gas concentrations and their consequent damage makes the heatwave case somewhat more comparable to the mesothelioma case where the claimant has multiple employers who may all have contributed to the harm. They were all liable.
But assume climate scientists were able to say that a given event was almost certainly caused by anthropogenic causes, as argued by James Hansen and others. With something like certainty as to cause, the court then only has to apportion what it sees as actual liability, not decide whether a defendant has made a sufficient contribution to an increased odds of harm.
Say you could show that Exxon Mobile is responsible for 3.2% of total anthropogenic climate change2. In either of our two example cases, the heatwave death or storm surge property damage, should the court simply apportion 3.2% of the damages to Exxon Mobile?
This solution has the appeal of simplicity. Exxon could counter that it would be unfair to make it pay damages without a similar calculation and percentage contribution from all other emitters. This theory would require a calculation of the contribution by, for example, every person driving a car, and would quickly make the case unworkable. Whether or not Exxon would succeed with this tactic would depend on the court's rules about co-defendants and its willingness to bring them in.
Even assuming Exxon lost that argument, it is not straightforward to determine what remedy rightly follows.
At the Adjudicating the Future symposium in London, supreme court judges and scholars from around the world discussed this issue of remedy. The notion emerged that even if everything lines up, courts may be reluctant to penalize Exxon, or other key carbon emitters, with monetary outlay for existing climate damages. Not because they are not liable but because the liability could become extremely large. Here Exxon's argument would be that if it were liable for 3.2% of the damage in a single heatwave or storm surge to one claimant, it will be similarly liable to all future claimants for all climate damages. With total damages from climate change that could reach somewhere between 2% and 20% of GDP per annum, even Exxon's deep pockets would feel the pinch. Jurists at the conference felt, however, that a reasonable approach would be to ask for a future-facing, not backward-looking, remedy.
Returning to our hypothetical Australian heatwave case, this could look as follows. Assume that a court agreed that the damage was caused by anthropogenic climate change, and the defendant, a coal-burning electricity producer in Australia, was — among other parties — liable for contributing to the harm. The claimant then follows the strategy the jurists were comfortable with, and does not ask for monetary damages. Instead, in a public-spirited and forward-looking manner, the relief requested is for the utility to restrict their greenhouse gas emissions by some large margin, driving future climate benefits. The interesting question is then whether a court would grant this relief.
Courts are in business to provide relief for proven harms, and tort law is the programme that delivers these results. It is hard to imagine that courts will fail to provide any relief for damages caused by climate change. The challenge will lie in presenting a harm that appeals to the sensibility of the court, causally connecting it via compelling science to the conduct of one or more defendants who could have done things differently once the dangers of climate change were known, and asking for a remedy that seems reasonable.
What can scientists do?
Keep developing credible and robust climate attribution science; see how you might be able to confidently argue that a particular event was (almost certainly) caused by anthropogenic greenhouse gases; and be prepared to testify as an expert witness in a case.
References
- Urgenda v The Netherlands C/09/456689/HA ZA 13–1396 (The Hague District Court, 2015)
- Goldenberg, S. Just 90 companies caused two-thirds of man-made global warming emissions. The Guardian (20 November 2013)
- XYZ and others v Schering Health Care and others EWHC 1420 (QB) (England & Wales High Court, 2002)
- Fairchild v Glenhaven Funeral Services Ltd and others UKHL 22 (UK House of Lords, 2002)
- Sienkiewicz v Greif (UK) Ltd UKSC 10 (UK Supreme Court, 2011)
- Ministry of Defence v AB and others UKSC 9 (UK Supreme Court, 2012)
- Christidis, N., Jones, G.S. & Stott, P.A. Nature Clim. Change 5, 46–50 (2015)
- Hansen, J., Sato, M. & Ruedy, R. Proc. Natl Acad. Sci. USA 109, E2415–E2423 (2012)
- Hadjiyianni, I. & Minas, S. 'Adjudicating the Future' symposium puts focus on courts in climate response. King's College London (2015)
- Carey, J. Calculating the true cost of global climate change Environment 360 (6 January 2011)
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