Climate litigation’s impact evaluation problem
Insufficient political progress in addressing the causes and consequences of climate change has driven many individuals, communities and civil society organisations to litigate in pursuit of climate justice. However, Nicholas Young argues, the practical effects of climate litigation remain largely unclear, underscoring the urgent need for more rigorous assessments of its impacts.
Over the last 40 years, more than 3,000 climate cases have been filed in nearly 60 jurisdictions across the world. Such legal mobilisation is likely to continue, and even accelerate, in light of the groundbreaking advisory opinions on the obligations of states with respect to climate change issued by the International Tribunal for the Law of the Sea, the Inter-American Court of Human Rights and the International Court of Justice. However, there is a problem: the impacts of these cases are, for the most part, poorly understood. As such, it is difficult to assess how effective climate litigation has been, and will be, in responding to climate change. This is especially concerning as the global carbon budget is rapidly being expended, jeopardising the temperature goals of the Paris Agreement and planetary, as well as human, health.
The most recent systematic review of the research literature noted that findings on the impacts of past climate cases are “brief, anecdotal and speculative in nature”. Aside from a small number of examples, scholars have rarely rigorously evaluated the impacts of climate litigation. Knowledge of these impacts is especially tenuous over long timescales and at the systems-level. At the same time, climate philanthropists’ efforts to evaluate the impacts of these cases have been considered “relatively embryonic”. Consequently, scholars have opined that “whether climate litigation is advancing or hindering climate action remains difficult to determine”. The Intergovernmental Panel on Climate Change (IPCC) has struck a similar tone, stating that the impacts of climate litigation are “unclear but promising”.
In this commentary, I outline specific consequences of climate litigation’s impact evaluation problem and suggest steps that may be taken to address it.
Consequences of the litigation knowledge gap
The knowledge gap with respect to the impacts of climate litigation has a range of consequences that undermine the effectiveness of climate litigation as a ‘regulatory tool’ of climate governance. For instance, it prevents the enabling conditions for effective climate litigation from being further understood, potentially reducing incentives for litigation stakeholders to scale up such actions and hindering their ability to strategically allocate resources across litigation and alternative means of advocacy, such as public campaigning and lobbying. Furthermore, the knowledge gap impedes the refinement of theories of change and related legal strategies, creating a risk that underlying assumptions go untested and strategic weaknesses persist. Put another way, opportunities for learning from experimentation and innovation in climate litigation are lost where rigorous impact evaluation is not undertaken.
Moreover, without rigorous impact evaluation, the efficiency of climate-related legal interventions is diminished. Scarce resources risk being misallocated and sensitive intervention points may be overlooked. Negative impacts, such as backlash or harm to affected communities, are less likely to be identified and mitigated, weakening the extent to which climate litigation may be socially responsible and effective. Lastly, without evaluation, funders and civil society actors cannot adopt a diversified ‘portfolio’ approach to climate-related legal strategies, as the risks and possible returns of different interventions cannot be accurately assessed.
This knowledge gap also has negative consequences for policy, as well as governments and firms and their responses to climate-related liability risks. Without data on litigation’s behavioural effects and regulatory contributions, regulation is less targeted and may duplicate efforts or overlook opportunities for leverage. In addition, unassessed litigation impacts obscure climate-related liability risks, possibly weakening deterrence effects on firms and governments and foreseeably delaying pro-climate behavioural change. Finally, without historical evaluation, forecasts on the future impacts of litigation are less reliable, a growing concern for financial regulators, insurers and other climate risk-sensitive actors.
Taken together, this knowledge gap has three broad negative consequences. It:
- Hampers the strategic, efficient and accountable use of climate litigation
- Limits climate litigation’s integration into broader climate governance
- Reduces climate litigation’s potential to enhance mitigation and adaptation efforts.
Accordingly, if the regulatory potential of climate litigation is to be realised, more robust evaluations of its impacts are essential.
Towards a bridging of the impact evaluation gap
Climate change is not the first issue which has prompted legal mobilisation intended to deliver social, political and economic change. As such, we can learn much from analogous historical strategic litigation efforts. Scholarship from neighbouring disciplines, such as policy evaluation, socio-legal studies, political science, development studies and sociology, can also provide a more comprehensive theoretical foundation upon which the impacts of climate litigation may be assessed. However, the possibilities of historical and cross-disciplinary analogy are constrained by unique features of the problem of climate change, including its size, multivalence, complexity and intertemporal character. As such, assessments of climate litigation arguably call for the creation and use of bespoke evaluation frameworks.
A conceptual framework for scoping climate litigation impact evaluations
Drawing on my recent research, which is inspired by those analogous strategic litigation efforts and neighbouring disciplines, I offer a starting point. Given that key variables in evaluations of climate litigation are often implicitly adopted and opaquely calibrated, I suggest a seven-variable conceptual framework for scoping climate litigation impact evaluations. The aim is to improve evaluations, making them more rigorous and easier to compare with each other.
This framework is not intended to overlook the fact that the impacts of climate litigation are shaped by their specific social, cultural, legal, temporal and institutional contexts. Rather, it is intended to engage with that complexity by providing a flexible conceptual framework that can be applied across different jurisdictions and types of climate cases, allowing those reviewing legal interventions to be more thorough and transparent in evaluating the impacts of climate litigation. The table below briefly addresses each of the variables in turn.
| Variables | Why it matters | What can be done |
| 1. Positionality | An evaluator’s own positionality invariably influences their work and should be reflected on to identify potential biases and blind spots | Reflect on personal and professional identities, ethical responsibilities and the interests potentially served or harmed by conducting an evaluation |
| 2. Intervention | Litigation is a process, and several points in that process can create impacts If the relevant ‘intervention’ is interpreted too broadly, the evaluation can become unwieldy | Precisely identify the intervention under evaluation, such as the filing of a case, delivery of a judgment or enforcement of remedies |
| 3. Dependent variables | As climate litigation can impact a vast array of people, environments and events, careful scoping is necessary to render its evaluation manageable | Carefully identify dependent variables to determine who or what is within the scope of the evaluation |
| 4. Materiality | Impacts vary significantly by magnitude. Clarity about which impacts are included in the evaluation enhances the evaluation’s rigour | Set a substantive threshold, such as a ‘materiality’ threshold, which determines which impacts merit inclusion in the evaluation |
| 5. Causation | The impacts of climate litigation exist on a spectrum of directness Setting a causation threshold improves internal validity and distinguishes impact evaluation from simply monitoring indicators | Set a causation threshold which establishes when an indirect impact will be attributed to an intervention Develop and use counterfactual scenarios to improve the robustness of causal claims |
| 6. Timescale | Impacts evolve over time, so evaluators should be explicit about the period over which they are evaluating impacts | Explain the timescale of the evaluation Conduct evaluations at different points in time to capture short- and long-term impacts of interventions |
| 7. Impact types | Climate litigation produces different kinds of impacts, such as material, legal and political impacts Recognising the differences in impact types can help guide evaluation method selection, enhance comparability and improve the communication of findings | Develop and use taxonomies of climate litigation impact types |
Source: Young N (2025). Climate Litigation and Impact Evaluation. Carbon and Climate Law Review 54 19(2)
When climate litigation impact evaluations expressly calibrate and engage with these seven variables, they are likely to be more robust, consistent and transparent. However, such a framework alone cannot overcome all barriers to more robust climate litigation impact evaluation. For example, impact evaluation will need to be both a higher priority for the climate litigation community, and better resourced, if it is to become more robust and strategically valuable. Moreover, sustained inter-organisational and interdisciplinary collaboration will be necessary to enhance the methodological rigour, comparability and decision usefulness of impact evaluations. Nonetheless, the framework suggested does address some of the conceptual barriers to climate litigation impact evaluation, and I hope it will encourage further iteration and development.
Realising the potential of climate litigation through more robust impact evaluation
Once-in-a-generation developments in international climate law, as well as huge volumes of domestic climate litigation, are foregrounding the role of law in response to the perils of climate change. However, whether the full extent of climate litigation’s potential will be realised depends on its impacts being robustly evaluated, understood and acted upon. Until then, climate litigation’s impact evaluation problem will limit the efficacy of legal action in contributing to mitigation and adaptation efforts — an unjustifiable concession given the scale of the climate challenge.
The author would like to thank Catalina Buciu at ClientEarth and Paul Benson for their helpful feedback on this commentary. The views in this commentary are those of the author and do not necessarily represent those of the Grantham Research Institute.
Nicholas Young is a Research Fellow in Sustainable Business Law at the Oxford Sustainable Law Programme and a DPhil candidate in Law at the University of Oxford. This commentary draws on his article, Young N (2025). Climate Litigation and Impact Evaluation. Carbon and Climate Law Review 54 19(2), which provides a more detailed account of climate litigation’s impact evaluation problem, why the problem exists, its consequences and possible mitigating steps.
Nicholas writes here in a guest capacity as part of our series coordinated by the Grantham Research Institute’s climate law and governance team exploring corporate climate litigation and the boundaries and interactions between science, the law and policy. The series contains contributions from legal scholars, economists and other social scientists, reviewed by practising lawyers. It is co-hosted with the Global School of Sustainability at LSE.
Other commentaries in the series:
- How states can overcome the challenges in regulating corporate climate transition plans (2 March, 2026)
- Bridging science and law for corporate climate accountability (26 February, 2026)