{"id":25750,"date":"2025-08-06T16:00:27","date_gmt":"2025-08-06T14:00:27","guid":{"rendered":"https:\/\/voelkerrechtsblog.org\/?p=25750"},"modified":"2025-11-14T15:06:49","modified_gmt":"2025-11-14T14:06:49","slug":"on-the-science-coloured-glasses-of-the-icj","status":"publish","type":"post","link":"https:\/\/voelkerrechtsblog.org\/de\/on-the-science-coloured-glasses-of-the-icj\/","title":{"rendered":"On the Science-Coloured Glasses of the ICJ"},"content":{"rendered":"

The ICJ gave a thoroughly science-based reading of State obligations with respect to climate change in its Advisory Opinion on Climate Change. This, in and of itself, is not very surprising considering the standard practice of domestic and human rights courts in climate cases, which are also known for heavily citing and relying on scientific evidence, mainly from the reports of the International Panel on Climate Change (IPCC). The Advisory Opinion, nevertheless, stands out, first, as compared to the ICJ\u2019s own previous environmental case-law, and second, for the way in which the Court is paving the way towards establishing state responsibility for climate harm with climate science evidence.\u00a0<\/span><\/p>\n

The Opinion suggests that scientific evidence is no longer a nuisance that should be avoided by the Court\u2019s reasoning as much as possible (see the majority\u2019s findings in <\/span>Pulp Mills<\/span><\/i><\/a>), or an extra-legal knowledge that is irrelevant for deciding the legal controversy. Long gone the days when members of the bench argued that adjudging science-heavy legal questions (in the material case, whether Japan\u2019s whaling program can be deemed scientific in nature) is \u201cmore suited to scientists rather than lawyers\u201d (see <\/span>Separate Opinion of Judge Sebutinde<\/span><\/a> in <\/span>Whaling<\/span><\/i>). Nor did the Court deem sufficient to pay only symbolic gestures towards scientific authority. Instead, it engaged with climate science meaningfully, assigning a central role to scientific knowledge in how the Court made legal sense of the climate crisis.<\/span><\/p>\n

Despite unanimous acceptance of climate science at large, judges had slightly different takes on climate science evidence, as transpires from several individual opinions. The main point of contention among members of the bench lies in whether the Court went <\/span>far enough<\/span><\/i> in relying on climate science. Judge Yusuf deems that the Court\u2019s reasoning as \u201cscientifically ill-grounded\u201d (<\/span>Separate Opinion<\/span><\/a>, \u00a716) for stopping short of legally recognizing what scientific evidence, in his view, suggests for States\u2019 responsibility for climate harm. Judge Nolte defended the Opinion\u2019s approach to conceptualizing wrongful acts and Judge Xue would have preferred more extensive legal reliance on per capita emission data provided by the IPCC.\u00a0<\/span><\/p>\n

Undoubtedly, the Court spared no efforts in weaving together legal and scientific knowledge in translating the \u201cmore than legal problem\u201d (\u00a7 456)\u00a0 of climate change to the language of international obligations and state responsibility. This short contribution will comment on how the Court was balancing factual and legal aspects in operationalizing the duty to prevent harm to the climate system and will discuss the ways in which climate science informs the content of legal concepts, with a special focus on how scientific evidence now may pave the way to a new legal paradigm of climate accountability.<\/span><\/b><\/p>\n

1. Science as the Backbone of the Judicial Findings<\/strong><\/p>\n

References to climate science runs through the Opinion as a consistent thread. With its 76 references to the term \u201cscience\u201d or \u201cscientific\u201d across the 133 pages, the Opinion indeed reads like the Court is openly using climate science knowledge as the main compass for navigating the uncharted waters of state responsibility for climate harm.\u00a0<\/span><\/p>\n

This was possible likely due to the pre-hearing meeting the Court held with members of the IPCC. The goal of the <\/span>day-long exchange<\/span><\/a> was \u201cto enhance the Court\u2019s understanding of the key scientific findings\u201d which the IPCC has delivered through its periodic assessment reports. Even though the exact questions and answers were not revealed to the public, it seems plausible that but for this substantive engagement with leading scientists, climate science could hardly fly so high in Court.<\/span><\/p>\n

Having declared that IPCC reports \u201cconstitute the best available science on the causes, nature and consequences of climate change\u201d (\u00a774), the Court went on reiterating the main findings of these reports (see pages 35-38), which is a standard practice of domestic courts in climate cases.\u00a0 What is more surprising is that the ICJ also used IPCC science as the starting point for basic definitions, such as \u201cthe climate system\u201d or \u201cmitigation\u201d, even though these very terms are also defined in climate treaties (but the legal definitions come only second in the Opinion after the respective scientific definitions, see \u00a775 and \u00a785).\u00a0<\/span><\/p>\n

The science-coloured glasses of the ICJ also enabled giving a holistic solution to the problem before it. Given the scientific fact that the climate crisis is inextricably linked to other human-enhanced planetary challenges, such as the ecological crisis or desertification, the Court included the Convention on Biological Diversity and the Convention to Combat Desertification among \u201cthe most directly relevant applicable laws\u201d – on the basis of primarily scientific justifications (\u00a7325, \u00a7331).\u00a0<\/span><\/p>\n

Climate science evidence also serves as the main epistemic justification for reaching almost every novel conclusion as to the content of legal obligations. Climate science lays the foundations for several key legal findings, including:<\/span><\/p>\n