2. Procedures and Evidence

3. CAUSATION TESTS

The following outlines the various tests employed to determine causation in climate litigation across the 17 legal systems surveyed. While the "but for" test and other similar stringent causation tests are commonly used, the unique challenges in establishing a direct link between the defendant's acts or omissions and harm in climate corporate litigation have led to the adoption of alternative causation tests.

Stringent Causation Tests

The "but for" test for factual causation in negligence claims, used in Australia, Canada, the UK, and the US, requires plaintiffs to prove that harm would not have occurred without the defendant's action or omission. Massachusetts v. EPA in the US is a pivotal case where the Supreme Court acknowledged the causal link between greenhouse gas emissions and global warming, establishing a precedent for recognising environmental harm and the contributory role of U.S. emissions.

German private law breaks causation down into two parts: the "conditio sine qua non" test, which looks for a factual causal link, and the doctrine of adequate causation, which considers whether an act significantly increased the risk of harm and if the injury was a foreseeable result of the defendant's wrongful act. Courts have been reluctant to affirm causality in climate cases, often dismissing claims on other grounds or avoiding the causality question altogether, except for the Higher Regional Court of Hamm in the RWE case, which chose to examine causality more closely.

In corporate climate litigation in the Philippines, causation is defined as the natural and continuous sequence, unbroken by any efficient intervening cause, which produces the injury without which the result would not have occurred. The concept of "proximate cause" requires a direct link between the defendant's actions and the injury, a requirement that poses significant challenges in climate change litigation due to the issue's global and complex nature.

Alternative Causation Tests

In situations involving multiple potential tortfeasors where plaintiffs cannot pinpoint a single tortfeasor as the cause of the injury, the "material contribution" test is applied in Australia, Canada, and the UK. This test is particularly relevant in cases involving multiple tortfeasors, which are common in corporate climate litigation, where it is unnecessary to apportion fault among the tortfeasors. In Canada, the elements of the "but for" test are: (i) a plaintiff's loss would not have occurred but for the negligence of two or more tortfeasors who are possibly responsible for the loss, and (ii) a plaintiff is unable to show that any one of the possible tortfeasors is necessary or but for the cause of the injury sustained.

In the UK, tort law's "but for" causation test is supplemented by alternative approaches for complex cases, allowing for liability based on "cumulative causation" and "material contribution to risk". Under the "material contribution to risk" test, a defendant can be found jointly and severally liable if they have made a material contribution to the claimant's harm. The "cumulative causation" test is used where the harm is cumulative and is likely to worsen with increased exposure, as seen in industrial disease cases like Fairchild v. Glenhaven Funeral Services Ltd. However, it is not guaranteed that this approach will be directly applicable to climate tort cases. Following the introduction of the 'special' material contribution to risk test in Fairchild, courts quickly sought to limit its application.

In Italy, injunction cases like those seeking emission reductions differ from traditional lawsuits, which demand proof of a direct causal link between a company's actions and specific harmful events. Instead, these cases require demonstrating how the company's conduct contributes to the perpetuation of hazardous climate conditions. Such lawsuits aim at companies for worsening the climate crisis through their emissions. This adjustment in the causation framework shifts the evidentiary focus towards establishing a link between the defendant's actions and the perpetuation of climate risks.

The Philippines court in the Segovia case proposed a "reasonable connection" test as a more viable approach for establishing liability in climate change litigation. This suggests an openness to adjusting legal standards to the intricate task of attributing climate change-related harms. Such adjustments include considering alternatives such as the "sufficient links" test recommended by the Philippine Commission on Human Rights' Report on the National Inquiry into Climate Change. The "sufficient links" test considers whether there are sufficient connections or links between the defendant's conduct (such as emitting significant amounts of greenhouse gases) and the broader impact on the climate, which contributes to the harm experienced by the claimant.