“Science and its connection to the law play a crucial part in securing successes in climate litigation.”

The basics of climate science state:

1. Climate change is happening.
2. It is caused by human activity.
3. Climate change has and will continue to cause harms.

It was not always the case, but this is now widely accepted by the scientific community, by judges at the domestic and international levels — and by fossil fuel companies finding themselves in court. So, how close are we to corporate climate accountability?

While climate litigants can take the above points as won, they now face the challenge of answering two key questions in court (1) whether climate change can be attributed to particular emitters, with liability arising for climate harms, and (2) whether a particular emitter’s targets or measures on climate mitigation or adaptation are, simply put, good enough. Claimants and their lawyers need to build effective arguments based on up-to-date climate science to address both. This blog will focus on the first question (see here for the second part on assessing targets and measures).

What is the context for corporate climate litigation?

Liability for corporate actors can be established through different causes of action. Lessons can be drawn from existing human rights litigation, and litigants have already shown different ways to seek corporate climate accountability.

The go-to database for climate lawyers – managed by Columbia’s Sabin Centre for Climate Change Law – counts 197 climate cases against corporate actors. The most common include:

- challenges to individual carbon-intensive projects (see the Sustaining the Wild Coast NPC case against Shell or the Australian Conservation Foundation case against Woodside);

- cases seeking to compel corporate actors to reduce their emissions (like the famous Milieudefensie case against Shell, won by the NGO at first instance and now on appeal);

- cases seeking remediation by establishing liability or imparting compensation for climate harms (see Lliuya v RWE); and

- cases focused on the obfuscation and misinformation from oil and gas companies (see cases brought by US states against Carbon Majors).

Climate science and causation: the role of attribution science

For a number of cases, particularly those seeking remediation, important questions have arisen around establishing causation.

As explained by Noah Walker-Crawford, Research Fellow at the LSE and key adviser in the Lliuya v RWE case, a notable obstacle is that “in climate claims against major corporate emitters, defendants have argued that climate science provides general knowledge about global warming but is not good enough to establish legal causation”. Litigants had faced similar issues in tobacco litigation “when defendants denied responsibility for health risks linked to smoking”.

Attribution science, experts say, is the key element to establishing legal causation in these climate cases. This field has rapidly developed and matured in recent years, with the publication of a number of peer-reviewed methodologies and specific event attribution studies. The international scientific advisory body on climate – the Intergovernmental Panel on Climate Change (IPCC) – recognised this; its conclusions on attribution of climate events to human influence significantly increased in confidence between its 2014 and 2022 reports. It pointed to the “advances in climate science” and “multiple lines of evidence” for our “improved understanding” of human activity and its effects on climate change.

The science has advanced so much there is now an “evidentiary gap” in climate cases brought by litigants around the world. Scientists have noted claimants and their lawyers should pay close attention to the “state-of-the-art” in climate science to maximise their chances. This entails a dialogue with different epistemic communities to understand how to effectively use attribution science, and collaboration to translate scientific causation into legal causation.

Walker-Crawford notes: “Scientists and lawyers often think about the world in different ways. Lawyers draw on evidence to build legal narratives about how governments and corporations should take responsibility for climate change. Scientists trace the processes of climate change with increasing precision, but highlight underlying uncertainties and limits to our knowledge. To build strong cases, climate lawyers must demonstrate that the scientific evidence is strong enough to fulfil legal standards of proof”.

If and when courts establish that liability against companies can arise for climate harms, this could have a wide-ranging ripple effect for loss and damage, climate justice, and the very existence of fossil fuel companies.

For part 2 of the blog on using climate science to assess targets and measures, see here.

Lucia Saborio Perez works in human rights and climate litigation, at Leigh Day’s International Department. She recently undertook a clerkship at the European Court of Human Rights and was previously with Greenpeace International’s Legal Unit and the Environmental Defenders Office. She has worked on state and corporate climate accountability cases and advisory proceedings across five continents and at three international courts.