Constructing the causal chain: attribution science in polluter pays climate litigation

Grantham Climate Litigation Guide 3

This guide, the third in a new series from the Grantham Research Institute at LSE and the Grantham Institute at Imperial College London, examines how evidence from attribution science is constructed and presented in courts to seek compensation from major greenhouse gas emitters for climate-related harm. Focusing on ‘polluter pays’ cases specifically, it explores the scientific and legal foundations of the evidentiary arguments used by claimants, examining concepts such as causation in law and standards of proof, as well as areas in which scientific and legal conversations overlap.

The guide is divided into three main parts:

• Part 1 is an overview of the scientific and legal foundations needed to understand claimants’ arguments in polluter pays litigation, introducing attribution science and outlining the legal bases in claims filed.
• Part 2 introduces the concept of a causal chain and outlines the three ‘causal links’ that claimants use to link a high-emitter to climate-related harm.
• Part 3 outlines how causal chain arguments are advanced in three European polluter pays cases.

The guide concludes with a reflection on the challenges and developments in polluter pays litigation.

Summary points

• In ‘polluter pays’ litigation, part of a rapidly expanding landscape of climate litigation targeting state and non-state actors, claimants must establish a causal relationship between a defendant’s greenhouse gas emissions and a specific incidence of past or future harm.
• Understanding and presenting this relationship to legal audiences can be complex, involving multiple disciplines and differing legal tests.  Attribution science, the field of climate science that seeks to understand the influence of anthropogenic emissions on the past and future climate, is increasingly used to support compensation claims from major emitters for climate-induced damage in these cases.  
• Rapid developments in attribution science mean that researchers can now quantify the emissions attributable to individual companies, assess how climate change has altered specific weather events and estimate the resulting damages.
• However, translating these scientific findings into legally sufficient evidence is challenging. Scientific and legal standards of proof differ, causation tests vary across jurisdictions, and the evidence needed to substantiate claims is diverse and technically complex.
• The causal arguments made in polluter pays cases can be understood in terms of a ‘causal chain’, an evidentiary framework that links emissions to harm. This chain can be divided into three ‘causal links’: focusing on damage or risk of damage, physical hazard and emissions. Three important European polluter pays cases highlight how this causal chain has been demonstrated by claimants: Luciano Lliuya v. RWE AG, Asmania et al. v. Holcim and Hugues Falys v. TotalEnergies.
• Polluter pays litigation cases face ongoing challenges, including the difficulty of meeting evidentiary standards, uncertainty around the adequacy of existing causation tests to account for climate-related harm and uneven data availability that may create disproportionate barriers for claimants in the Global South.
• Despite these barriers, polluter pays litigation has seen some court decisions favourable to claimants. Furthermore, several developments in the area – including advances in end-to-end attribution methodology, the potential extension of claims to the financial sector, and moves towards greater communication between scientific and legal communities about their different needs and limitations – may lead to more polluter pays claims in the future.

DOI: 10.21953/researchonline.lse.ac.uk.00138281

About the Grantham Climate Litigation Guides

These guides are a collaboration between the Grantham Research Institute at LSE and the Grantham Institute at Imperial College London. The series is designed to provide informed guidance on the use of climate science and evidence in legal and policy contexts in concise, non-technical language. Further guides will be published in 2026.