HKA hosted a panel session during London International Disputes Week earlier this month. Entitled Litigation Risk in a Warming World, the panel included experts on carbon emissions and reporting, climate science and attribution, and the quantum of damages, mitigation and insurance. We were also delighted to be joined by two leading barristers in climate litigation.

With many thanks to our speakers, the panel was able to address the four key steps of: 

1. Quantifying the contribution of a corporation or state to global warming,
2. Determination of the attribution of this global warming to the increased likelihood and magnitude of specific events,
3. The legal argument, and
4. Agreeing costs.

Dr Matt Ösund-Ireland from HKA considered how far back in time we need to go when calculating an individual company or state’s contribution to global warming. The answer depends on when the company or state was able to foresee the harm caused by global warming.

At the international level, a more politic approach might be to say, “let’s all agree we start counting from this date forward.”

Whichever start date is agreed, there is clearly substantial work to be done to sufficiently describe the company’s or state’s historical activity and to back project annual emissions data. The risks of misreporting or greenwashing, or the failure of carbon offset schemes, also need to be considered, which suggests we may expect a more forensic accounting type approach to any investigation, going beyond the requirements of carbon reporting as part of annual disclosures.    

Factors driving extreme events and trends in climate change

Professor Piers Forster from the Climate Change Committee then provided a description of the factors driving extreme events and trends. This was fortunate timing as Prof. Forster was able to draw on Indicators of Global Climate Change 2025, which was published a few days after the event. He highlighted that human‑caused warming reached c.1.37 °C in 2025, with the rate of warming at a record high. This means the world is very close to the 1.5 °C Paris target with very little headroom remaining. The growth in greenhouse gas emissions is slowing but emissions remain near all‑time highs, driving continued warming. In fact, the Earth is heating faster with the energy imbalance more than doubled since the late 20th century. This means the planet is accumulating heat faster, mainly in the oceans, which is driving future warming and contributing to sea‑level rise. Marine heatwaves have more than tripled since the early 1990s, global sea level continues to accelerate upward, and extreme land surface temperatures are rising rapidly. In summary, climate impacts and extremes are clearly intensifying.

How attribution can be grounded in the impact of climate change on protected human rights

Sudhanshu Swaroop KC from TwentyEssex considered different types of legal claims in which attribution science might be relevant. In relation to international law claims, he considered the relevance of attribution science to the question of whether a state can be held responsible for breaching international law obligations regarding climate change, in light of the recent Advisory Opinion of the International Court of Justice. In relation to human rights claims by an individual against a state, he considered the judgment of the European Court of Human Rights in KlimaSeniorinnen v Switzerland, in which the Court derived obligations concerning climate from Article 8 of the ECHR, without any particular reliance on attribution science. In relation to tort claims by individuals against corporations in domestic courts, he considered the German case of Lliuya v RWE, in which the German courts relied significantly on attribution science in their analysis, although they ultimately dismissed the claim on the facts.

International Court of Justice’s advisory opinion

Wendy Miles KC, also from TwentyEssex, focused on how the International Court of Justice (ICJ), in its July 2025 advisory opinion, provides a broader framework for state responsibility. The opinion confirms that states have binding obligations to prevent significant climate harm and that breaches can constitute internationally wrongful acts, engaging responsibility and potentially requiring reparations. The ICJ also accommodates the cumulative and shared nature of climate causation, allowing attribution without the need for strict, exclusive causal proof, and leaving detailed questions of causation to be assessed in context.

Finally, the panel turned to discuss Quantum, with Loes van Bohemen from HKA and Dr Tony Rooke from Howden Group. Loes explained that quantifying damages from climate-related events can be done using methodologies similar to those used in other types of damage litigation. There are well-established methods in the economists’ toolkit for calculating losses of profits, property damage, and non-material damages. Tony set out that, in the face of climate change, there are more areas of the world where fire and flood insurance is no longer available due to increased risk and affordability constraints. This has necessitated government-backed interventions, such as the UK’s Flood Re initiative, to make flood cover more widely available in the UK. On the other hand, Tony also observed that some risks associated with carbon emissions and litigation remain underpriced, and that the rise of climate litigation is not yet perceived as a significant risk to corporations.  

What is next?

As we move on from a busy June, with LIDW and London Climate Action Week, HKA is not willing to end the conversation. We will continue to draw on expert and legal knowledge, collating a wide range of views and opinions for a Special Report to be released later this year. Let us know if you want to be involved.

 

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About the authors

Dr Matt Ösund-Ireland is a Chartered Environmentalist with over 30 years of experience in supporting commercial organisations, governments and financial institutions with strategy, environmental compliance, impact assessment and due diligence. Matt holds a doctorate in local air quality management and climate change and a degree in combined science. He is a Member of the Institution of Environmental Scientists and the Institution of Air Quality Management.

Loes van Bohemen is an economist with over 10 years of experience. She has assisted the named damages expert on several occasions. Loes has been involved in arbitration and litigation proceedings regarding competition and commercial damages in the Netherlands and the UK. Loes is dual-qualified in law and economics. She is a member of the European Competition Lawyers Association and the Association of Competition Economics.