The decade since the 2015 Paris Agreement has seen a surge in attention to corporate responsibility for the transition to net zero, leading to a plethora of standards, campaigns, advice, and guidance for companies (3). These range from initiatives led by nongovernmental organizations and investors to campaigns and standards adopted by more authoritative intergovernmental bodies.

One of the clearest articulations of corporate climate responsibilities is found in the 2023 update to the Organisation for Economic Cooperation and Development (OECD) Guidelines for Multinational Enterprises. The guidelines are not directly binding on companies, but member states are required to promote their implementation. Under the guidelines, companies should ensure that their emissions are consistent with internationally agreed-upon global temperature goals. The means for achieving this is through “the introduction and implementation of science-based policies, strategies and transition plans on climate change mitigation” [(4), p. 37] as well as the adoption of emissions targets, which should be science based and include scope 1, 2, and 3 greenhouse gas (GHG) emissions. Transition plans—structured frameworks that outline how companies intend to reduce emissions—have become a central mechanism for ensuring corporate accountability.

The integration of such obligations into the guidelines can be seen as part of a broader process by which voluntary and soft law norms have started to harden into more legally binding ones. There has been a surge in regulatory instruments concerned with company net zero targets and transition plans (3). Such instruments demonstrate considerable variance in their form, scope, and level of stringency; however, at least in certain regions, a trend toward binding requirements for corporate transition plans can be observed (3). This builds on older legislation that established corporate obligations to conduct mandatory human rights and environmental due diligence (e.g., France’s 2017 duty of vigilance law). In the absence of mandatory climate due diligence standards, litigants brought claims that framed climate-related harms as a human rights and environmental issue, and thus mitigation forms part of responsible business practices (e.g., Notre Affaire à Tous and others v. Total).

At present, the most notable piece of corporate transition plan legislation is the European Union’s Corporate Sustainability Due Diligence Directive (CSDDD), which forms part of a broader suite of legislation aimed at aligning firm activity with the goals of the European Green Deal (5). The CSDDD requires companies that meet certain threshold criteria to “adopt and put into effect a transition plan for climate change mitigation which aims to ensure, through best efforts, that the business model and strategy of the company are compatible with…the limiting of global warming to 1,5°C in line with the Paris Agreement and the objective of achieving climate neutrality as established in Regulation (EU) 2021/1119” [(5), p. 43]. Companies’ plans shall include “time-bound targets” based on “conclusive scientific evidence” and “where appropriate” may include absolute emissions targets for scope 1, 2, and 3 GHGs.

For legislation to work effectively, guidance needs to be formulated for companies on how to translate overarching temperature or timebound climate neutrality objectives into emissions pathways in practice. In developing guidance that is as clear and concrete as possible, policy-makers will be presented with challenges similar to those faced by the judges in the Milieudefensie case in translating state-of-the-art research and science.

When existing regulatory mechanisms do not produce sufficiently climate-aligned outcomes, litigation can compel governments and corporations to take more ambitious action. Historically, most climate-related legal claims, both overall and in terms of success, have been against governments, but an expanding category of cases targets corporations (6). These claims require robust scientific evidence on how corporate behavior affects climate change and climate policy outcomes. The type of evidence required depends on whether the claimants seek to hold corporations responsible for past conduct (“backward-looking” cases) or to change future corporate behavior in line with climate targets [“forward-looking” cases (6), such as Milieudefensie].

Although academic discussions about the use of climate science in litigation have burgeoned in recent years, much of this has focused on backward-looking corporate claims. In those cases, attribution science often plays a critical role in linking companies’ GHG emissions to global climate change and local impacts. Forward-looking cases typically require evidence about what levels of emissions reduction are required for corporations to stay in line with global and national targets. Although the Milieudefensie case is the most high-profile case in this category—and the only one resulting in a successful court judgment until the Hague District Court’s initial decision was overturned in 2024—there are more than 20 other forward-looking cases pending around the world (6). A key question for courts is to determine whether and how global or sectoral pathways should be applied to individual companies. Unlike with backward-looking cases and attribution science, there has been little academic discussion about how this type of science can be applied in litigation.

Although there is a long tradition of setting emissions targets at the international and national levels, the science of corporate target setting is less developed (7). A fundamental challenge is to translate global climate targets into actionable corporate commitments (i.e., from global temperatures to company emissions of different scopes). A primary concern is to ensure that targets are meaningful, especially because corporate targets tend to be voluntary.

Several methodologies exist to facilitate this process. Simpler approaches apply global or regional emissions reduction rates uniformly across all companies (8). This logic was partially followed in the Milieudefensie case. Milieudefensie presented the global emissions reduction rate target as a baseline minimum that Shell should meet or exceed on the basis that Shell, as one of the largest contributors to climate change, bears a greater legal duty to reduce emissions compared with other entities.

More sophisticated methodologies account for variations in mitigation potential and economic costs across companies, typically by differentiating between the economic sectors to which companies belong. Decarbonization challenges can vary strongly across sectors such as aviation, electricity, and steel. Top-down methodologies use the outputs of IAMs to derive company emissions pathways on either an absolute or intensity basis (see the figure).

A prominent example of a methodology like this is the Sectoral Decarbonization Approach (SDA) (9). The Science-Based Targets Initiative (SBTi) has operationalized the SDA and has now validated more than 4000 corporate emissions targets using this methodology as a benchmark. The Transition Pathway Initiative (TPI) similarly applies a variant of the SDA to independently assess whether companies’ emissions pathways align with sector-specific benchmarks. TPI’s analysis is an input to the Net Zero Company Benchmark of Climate Action 100+, the world’s largest investor-led engagement initiative on climate change.

The SDA has been applied to the O&G sector using a scope of emissions that includes not only scopes 1 and 2, to which most methods of calibrating corporate emissions targets have been restricted, but also scope 3, category 11—use of sold products (i.e., customers’ burning O&G), which is the dominant share of life cycle emissions from the sector (10). These emissions can be normalized by energy sales to create a production-based intensity measure or be used directly as an absolute emissions measure. With the former measure, O&G companies are benchmarked against the emissions intensity of the whole energy sector. O&G companies can reduce their emissions intensities by diversifying away from fossil fuels toward renewables, which is the strategy being followed by O&G companies that are most advanced on climate change. Absolute emissions would be an appropriate way to benchmark companies whose climate strategy is instead to manage decline, noting that no company has so far set such a strategy. Similarly, IAM output has been used to derive pathways for fossil fuel companies’ absolute production (11).

The key point is that methods exist, published in peer-reviewed academic journals, to derive sectoral pathways for O&G companies such as Shell. So, why was the Court of Appeal reluctant to draw on these methods? The Court’s decision might be considered unexpected given that global or national and sectoral pathways draw on the same kind of evidence—IAMs run to comply with global temperature targets. The origin of the net zero by 2050 goal, for example, is the representative time at which IAMs synthesized by the 2018 Intergovernmental Panel on Climate Change (IPCC) Special Report on 1.5°C reached net zero carbon dioxide (CO₂) emissions (12).

It is fair to say, however, that sectoral pathways currently command less confidence than global pathways. Pathways at all levels must contend with the fact that different assumptions (e.g., on socioeconomic pathways, deployment of carbon capture and storage, and others) can lead to very different projections, with the range reflecting not just technical uncertainty but also competing normative visions of a low-carbon world. However, this is currently a more acute problem for corporate pathways because fewer IAM-based emissions scenarios are available at the sector level. This partly reflects that many IAMs lack detailed sectoral resolution, and where such data exist, they are not always publicly available. So, although the aforementioned goal of net zero by 2050 was established by looking across a wide range of IAMs, sectoral pathways are typically based on a more limited set of IAMs, and some sectors (e.g., energy) benefit from more IAM data than others. With fewer models, the analysis is less robust. There is also more uncertainty about sectoral compared with economy-wide pathways because forecasting errors in each sector will be, to some extent, idiosyncratic (as they relate to, for example, sector-specific technologies).

Emerging literature on corporate pathways has also identified further contestable assumptions in how IAM outputs are used by methods such as the SDA. It can be difficult to ensure that the aggregate of corporate commitments is consistent with global climate goals. Selecting a pathway for one sector has implications for other sectors given economic and emissions interdependencies. Existing frameworks, such as SBTi, effectively allocate future emissions allowances to companies in proportion to a company’s past and current emissions and thereby ignore historical exceedance of benchmarks (13). Instead, it might be considered fair to hold companies accountable for historical emissions in excess of their benchmark, in which case company and benchmark pathways should start in the same base year (e.g., 2015 to coincide with the Paris Agreement), and, logically, future excess company emissions would also lead to a readjustment of their benchmarks.

More broadly, IAMs are optimization models, which means that they seek a cost-minimizing distribution of emissions reductions across sectors. Although this ensures that mitigation efforts are allocated where they are most cost-effective, it does not inherently account for principles of fairness, equity, or historical responsibility in the distribution of emissions reductions. In theory, the cost-minimizing distribution of emissions reductions can be accompanied by climate finance and transfer payments to reconcile economic efficiency with more equitable costsharing. However, in practice, the political and economic feasibility of such transfers remain highly uncertain. As a result, IAM-derived pathways may not align with all stakeholders’ expectations of fairness in corporate or national climate commitments. In cases against governments, courts can more easily rely on distinctions drawn in the United Nations framework and IPCC reports between expectations on developed and developing countries. Ultimately, there is, as of yet, no repository of corporate climate benchmarks that is underpinned by the same body of peer-reviewed scientific evidence and meets the same standards of transparency as the IPCC’s global scenarios. However, the legal duty of care is inherently dynamic, defined by applicable laws and evolving social norms of conduct. Liability is a factual and normative assessment of a particular defendant’s behavior. In the Milieudefensie case, the Court recognized differentiated responsibilities among companies, noting that as a major O&G producer, Shell carried a “special responsibility” (1). Normative assessments of IAM-derived sectoral pathways require judges and lawyers to engage with the underlying science, assumptions, and limitations.

Below, we review three approaches that could help strengthen forward-looking cases seeking to improve corporate accountability for climate harms. Understanding ways forward is relevant both for national courts that interpret companies’ duty of care under relevant legal regimes in their jurisdiction as well as policy-makers seeking to impose transition plan requirements on companies within their jurisdiction or control.

This work received support from the Grantham Foundation for the Protection of the Environment (S.D., J.S., C.H., T.C., N.W.-C., and F.V.), the TPI Centre (S.D.), Economic and Social Research Council grant ES/Y003314/1 (N.W.-C.), and Engineering and Physical Sciences Research Council grant PATCH project EP/W027887/1 (F.V.).w