2. Procedures and Evidence

1. OVERVIEW

One crucial aspect of determining corporations' liability in climate litigation is establishing "causation," i.e., demonstrating that they caused the harm. This Section explores the compelling evidence plaintiffs have presented to prove causation and examines how courts assess the adequacy of plaintiffs' evidence. This assessment is based on "causation tests," standards of proof, and rules regarding who bears the burden of proof.

In the realm of corporate climate litigation across the 17 case-study countries, a variety of causation tests are employed. The "but for" test, used in countries such as Australia, Canada, the UK, and the US, necessitates that plaintiffs prove harm would not have occurred without the defendant's actions or that the defendant's actions significantly contributed to the harm, a concept epitomised by the Massachusetts v. EPA case in the US. Similar stringent causation tests include the "conditio sine qua non" test (in Germany), which looks for a factual causal link between the defendant's act and the injury, as well as the doctrine of adequate causation (in Germany) and the doctrine of proximate cause (in the Philippines).

Some jurisdictions, such as the UK, supplement the stringent causation tests with alternative approaches for complex cases, allowing for liability based on their "material contribution" to harm and "cumulative causation". Similarly, in Italy, injunction cases necessitate demonstrating how a company's conduct contributes to the worsening of the climate crisis rather than directly causing it. In the Philippines, the traditional "proximate cause" concept faces challenges due to the global nature of climate change, leading to the adoption of a "reasonable connection" test and a "sufficient links" test as a more viable approach to establishing liability.

Moreover, legal systems around the world employ a variety of procedures for handling evidence and determining causation. A fundamental principle across jurisdictions is the burden of proof, typically placed on the party asserting a fact. However, an emerging trend in some jurisdictions, like China, is the reversal of this burden in environmental cases, requiring defendants to demonstrate their actions did not cause harm. While not universally adopted, other jurisdictions show openness to similar concepts through Germany's presumption of causality and Poland's presumption of unlawfulness, strict liability, and acceptance of prima facie or indirect evidence. These approaches effectively shift the evidentiary burden to defendants, particularly in complex environmental cases. Additional procedural tools, such as the application of the precautionary principle in China and the doctrine of res ipsa loquitur in the Philippines and Nigeria, aim to mitigate the inherent challenges in proving causation in environmental litigation.

Furthermore, the standard of proof required to establish causation varies, ranging from a "high level of probability" to a "reasonable connection", depending on the legal context and the nature of the case.

Finally, scientific evidence and expert testimony are paramount across the 17 jurisdictions studied, with reports from bodies like the IPCC crucial for linking corporate actions to climate change impacts. However, despite advancements in evidentiary standards and legal frameworks, challenges remain. The complexity of climate science and the global impact of greenhouse gas emissions present persistent obstacles. For example, the "market substitution" argument, which suggests that blocking one environmentally harmful project could simply lead to its replacement by another similar project elsewhere, thereby not reducing overall greenhouse gas emissions, complicates the direct linkage between specific projects and their net impact on greenhouse gas emissions. Consequently, there is an ongoing debate about the adequacy of current causation tests and the potential need for their revision to more accurately address the complexities of corporate climate litigation.