The Role of Attribution Science in Climate Litigation: 3 Case Studies

While it is well-established that human activities, from industrial emissions to deforestation, drive climate change, pinpointing responsibility for specific climate-related disasters is far more complex. With global carbon dioxide levels now surpassing 419 parts per million—more than 50% higher than pre-industrial levels—extreme weather events have become both more frequent and more devastating. Yet, holding corporations accountable for their emissions often requires rigorous evidence that ties their actions directly to these climate impacts. This is where attribution science has become essential.

Attribution science focuses on determining the extent to which human activities, particularly greenhouse gas emissions, contribute to specific climate events such as heatwaves, storms, and droughts. Using data and climate models, scientists compare real-world scenarios with hypothetical ones where human influences are absent, assessing how much human activity has increased the likelihood or severity of an event. This approach has significant implications for climate litigation, providing a scientific basis to hold polluters accountable for damages linked to extreme weather events.

This field is largely supported by the works of climate researcher Richard Heede who demonstrated in his 2013 and 2014 studies that 63% of global carbon dioxide and methane emissions between 1854 and 2010 could be traced to just 90 entities, the so-called "Carbon Majors." His work highlights a relatively small group of corporate and state-owned fossil fuel producers as disproportionately responsible for greenhouse gas emissions, laying the groundwork for the Carbon Majors Database. This database now serves as a tool in climate litigation, allowing plaintiffs to leverage historical emissions data to support claims against major emitters and advance accountability frameworks in climate policy and regulation.

As attribution science matures, it plays a pivotal role in legal battles worldwide, where plaintiffs demand justice for damages ranging from property loss to health impacts. This article explores 3 landmark cases where attribution science has shifted or is still shifting, the dynamics of climate litigation, providing a scientific basis for establishing liability, seeking reparations, and pushing corporations to confront their role in the escalating climate crisis.

Attribution science spans several specialized approaches—climate change attribution, extreme event attribution, and source attribution—each uniquely suited to support legal arguments, pinpointing the extent of human influence on observed climate patterns and environmental disruptions.

• Climate Change Attribution
  Climate change attribution plays a pivotal role in understanding how long-term human activities, such as fossil fuel use, deforestation, and industrial emissions, drive broader climate trends like rising temperatures, shifting precipitation patterns, and sea-level rise. Comparing climate models that simulate conditions with and without human influence, this approach isolates anthropogenic impacts and quantifies their effect on natural climate baselines. In court, these findings offer strong evidence for plaintiffs aiming to demonstrate that defendants’ actions have significantly altered climate patterns, underscoring the need for accountability and reinforcing claims under international agreements like the Paris Accord.
• Extreme Event Attribution
  Extreme event attribution zeroes in on specific instances of extreme weather, such as hurricanes, heatwaves, and floods, to assess whether these events have been intensified through human-caused climate change. Using statistical analysis and climate models, this branch of attribution science compares the frequency and severity of recent events with historical data. For litigators, such findings help argue that certain communities have suffered disproportionate impacts due to intensified events linked to corporate or governmental inaction on climate change. As a result, extreme event attribution has become crucial for cases seeking compensation for damages and increased protections for vulnerable regions.
• Source Attribution
  Source attribution provides precision, identifying the origins of greenhouse gases or pollutants driving environmental harm, whether from industrial sectors, agriculture, or specific regions. Techniques like carbon isotope analysis and air quality monitoring allow tracking of emission sources, which is critical for legal cases against high-emission industries. Targeting specific emitters, plaintiffs can establish a clearer line of responsibility in pollution-related claims, and in transboundary pollution cases, source attribution offers scientifically-backed data for international legal actions that advocate cooperative emission reduction.

Each type of attribution science delivers unique insights that collectively strengthen the evidentiary basis for climate litigation. Through a clearer understanding of causality in environmental change, attribution science offers a robust foundation for legal frameworks to address the increasing impacts of climate change, holding major emitters accountable, and advancing equitable redress for affected communities and individuals. The following examples illustrate how these methodologies support policy-oriented legal strategies designed to confront climate risks and drive responsible action among high-emission contributors.

In Lliuya v. RWE, a Peruvian farmer and mountain guide, Saúl Luciano Lliuya, brought legal action against the German energy company RWE in 2015. The case emerged from Lliuya's argument that RWE’s significant contributions to global greenhouse gas emissions made it partly responsible for the melting glaciers in Peru, which, in turn, intensified the risk of flooding in his community. Specifically, Lliuya contended that RWE should bear a share of the financial burden for protective measures needed to address the rising flood risk in his home region near Huaraz, in the Andes Mountains. He argued that RWE, as one of the largest greenhouse gas emitters in Europe, contributed approximately 0.47% of global carbon emissions and thus should contribute a corresponding share to the preventive adaptation costs.

German courts initially rejected the claim in 2016; however, on appeal, the Higher Regional Court of Hamm ruled that Lliuya’s case could proceed, establishing a precedent for corporate liability in transnational climate impacts. This ongoing case raises broader questions about corporate accountability and the mechanisms through which transboundary environmental harm is attributed and addressed.

Milieudefensie et al. v. Royal Dutch Shell, filed by environmental organization Milieudefensie (Friends of the Earth Netherlands) and several co-plaintiffs, is a landmark climate litigation case decided in 2021 by the District Court of The Hague. The plaintiffs argued that Shell’s business operations and future investment plans were incompatible with the Paris Agreement’s goals of limiting global warming to 1.5 degrees Celsius. They sought a court mandate to compel Shell to align its policies and business activities with these international climate targets by reducing its net emissions by 45% by 2030 relative to 2019 levels.

The court's decision was commendable; it ordered Shell to drastically reduce its carbon emissions across all operations and its value chain, marking the first time a court imposed such an obligation on a private company. This ruling underscored that corporate strategies contributing to climate change could be deemed unlawful if they fail to meet global climate agreements. Shell was mandated to act with "obligations of result" and to take tangible actions to mitigate its climate impacts. This case has had wide-reaching implications, prompting other companies and investors to consider the legal risks associated with insufficient climate action and to integrate emissions reduction targets more seriously within their corporate governance frameworks.

In Asmania et al. v. Holcim, four individuals from the Indonesian island of Pulau Pari initiated a lawsuit against Holcim, a leading global cement manufacturer headquartered in Switzerland, in 2022. The plaintiffs claimed that Holcim’s emissions, which constitute a significant share of global industrial greenhouse gases, directly contributed to rising sea levels that threatened their island home with the risk of submersion. Pulau Pari is among the small island communities highly vulnerable to sea-level rise, where frequent flooding and saline intrusion are already impacting the local population’s livelihoods and ecosystem integrity.

The plaintiffs demanded that Holcim compensate for damages and contribute to necessary adaptation measures to protect Pulau Pari. They argued that Holcim’s historic and ongoing emissions have substantially contributed to global warming and thus to the increased climate risks their community faces. While the case is still ongoing, it reflects a growing trend among vulnerable communities to seek redress through the courts and demand accountability from large corporations with significant emissions profiles.

Improving attribution science for climate litigation rests heavily on refining data quality, understanding natural variability, addressing model limitations, and bridging the gap between legal and scientific causation. Attribution science has made substantial progress, yet the field still encounters substantial challenges, particularly when it comes to linking specific emitters to precise climate-related impacts.

At the foundation lies data quality and availability. High-quality climate data and climate model allows for a more granular understanding of climate variables and strengthen attribution science’s reliability. However, gaps in regional datasets and inconsistencies in historical data limit precision. Reliable and accessible datasets from satellite monitoring, local weather stations, and climate surveys could aid scientists in forming more definitive links between emissions and specific climate events, offering a clearer view of the role of individual contributors. An analogy would be trying to solve a jigsaw puzzle with missing pieces: while you can see parts of the picture, essential details remain obscured, affecting the reliability of any conclusions drawn.

Adding complexity, natural variability often masks the influence of human-induced climate change, particularly in the context of extreme weather events. Climate systems are inherently variable, and understanding this “background noise” is essential for pinpointing human contributions. The difficulty here is akin to distinguishing the sound of a single instrument in an orchestra—while individual patterns exist, they’re often hard to isolate without distorting the broader context.

Model limitations also play a role. Attribution science depends on climate models that simulate both natural variability and human influences, yet capturing localised, extreme events accurately remains a challenge. High-resolution models are advancing but can still struggle with small-scale phenomena, like flash floods or regional heatwaves. For effective litigation, these models must become more precise in representing the unique processes of different climate events. Though improved, they often lack the finesse to isolate certain impacts, leaving room for legal challenges that weaken the scientific case in court.

Finally, a fundamental distinction exists between legal causation and scientific causation. While scientific causation accepts probabilistic evidence to establish links between emissions and impacts, legal causation typically requires a more definitive “but-for” standard. This discrepancy often leaves attribution science on uncertain ground in courts, where judges may struggle to interpret probabilistic data that doesn’t adhere to conventional causation models. Bridging this divide requires both scientific advancement and a legal paradigm that recognises the complexities of climate attribution, thus ensuring that the science supporting climate litigation is not only robust but also understandable and actionable.