Vanessa Laukkanen and Vendela Laukkanen are recent graduates from the University of Cambridge with LLM degrees in International Law


First things first – climate change is caused by human activities through the emissions of greenhouse gases (GHGs) and refers to global warming, i.e. the increase of the average global temperature, causing more frequent and extreme weather events resulting in damage to nature and humans.[1] In this regard, ‘tipping points’ describe the ‘point of no return’, i.e. where the threshold in a climate system is reached as an effect of combined smaller acts, which leads to an irreversible change in that system.[2] The International Community may have already reached a tipping point,[3] and there is no ‘credible pathway to 1.5C in place’,[4] which prompts the urgent need to find a way to hold the major emitters of GHGs responsible for the adverse effects of emissions. Indeed, Principle 22 of the 1972 Stockholm Declaration demonstrates that States shall

‘develop further the international law regarding liability and compensation for the victims of…environmental damage ….’

The principle thereby recognises the importance of environmental liability as well as compensation. Such liability is essential to protect the environment, to make the major polluters pay for the damage of their actions and bring some sort of justice into the conversation. However, the current state of the International Law of State Responsibility is inadequate in finding responsibility for the most pressing concern of our time. Here is why.

The Law of State Responsibility in the Environmental Context

Under the Law of State Responsibility, a breach of a primary international obligation through an act or omission attributable to a State gives rise to a secondary obligation – to cease the wrongful behaviour.[5] Whilst this is relevant in the environmental context, the following describes the uncertainty of the applicability of international responsibility in the context of climate change.

The Uncertainty of the Legal Status of International Environmental Norms

As stated above, for there to be international responsibility in the first place, there must be a primary obligation for States to act in accordance with, a breach of which will trigger the application of international responsibility. It is here where the difficulties begin. Whilst International Environmental Law offers multiple important principles to influence environmental climate change agreements, such as common but differentiated responsibilities (CBDR) and the precautionary principle, their legal status is contested; hence, their utilisation in litigation is limited.[6]  Therefore, when the primary obligation is unclear,  the application of the secondary obligation becomes opaque, and the fundamental difference between such obligations becomes uncertain and may, as such, be ineffective in litigation with respect to the responsibility of a State in the climate change context.[7]

The Prohibition of Transboundary Harm: a Cure?

Nevertheless, State practice seems to support the prohibition of transboundary harm. Indeed, it has been recognised in Principle 21 of the Stockholm Declaration and the preamble of certain treaties, such as the United Nations Framework Convention on Climate Change. International case law also presents a number of instances where Courts have recognised the prohibition to cause transboundary harm: in Trail Smelter, the Court found that:

‘no State has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another… when the case is of serious consequence and… established by clear and convincing evidence.’

Accordingly, the ICJ, in its Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, recognised:

‘the existence of the general obligation of States to ensure that activities within their jurisdiction… respect the environment of other States.. is now part of the corpus of international law….’

The more recent case of Costa Rica v Nicaragua further found that:

‘…damage to the environment, and the consequent impairment or loss of the environment to provide goods and services, is compensable under international law.

The case law, therefore, demonstrates a promising view – that States cannot harm the environment of other States and not be held accountable; accordingly, the element of compensation for such damage should be highlighted. However, it is important to emphasise that none of the cases refers specifically to the issue of climate change or ‘smaller acts’ that trigger ‘tipping points’. There is a difference between a situation as in Trail Smelter, where only one State permitted the harmful act that caused damage to only one other State, and the more complex situation where multiple States are complicit in the activities causing the harm, i.e. the emissions of GHGs. It is, therefore, unclear how the prohibition on transboundary harm would apply in a case where the damage is caused multilaterally because of the collective nature of climate change and the triggering of tipping points.

Evidentiary Difficulties

If one were to assume that there is a clear primary obligation applicable, such as the prohibition to cause transboundary harm, to a situation where a State’s environment has been damaged by another State’s emissions of GHGs, the complainant State/s would still face evidentiary difficulties in litigation.[8]

The Court in Trail Smelter set out the conditions of ‘serious consequence’ and the high evidentiary threshold of ‘clear and convincing evidence’, thereby requiring clear causation. This further relates to another feature of the Law of State Responsibility that is particularly difficult in the context of climate change – to prove a causal link between the harm and the acts of a particular State. To emit GHGs is not a prohibited act under International Law, but to cause harm to another State’s environment is. The harm must therefore be attributable to a State’s emissions of GHGs.

Causation usually involves two examination stages: general causation and specific causation, also referred to as the ‘but for test’, which asks whether the harm had occurred but for the conduct of the respondent state.[9] General causation is less challenging to prove since there is a scientific consensus on the general link between GHG emissions and climate change, which can be scientifically linked to harmful consequences.[10] However, it becomes more complex when the law demands proof of a specific harm caused by a specific actor. Holding a State responsible for conduct that results in ‘tipping points’ under the Law of State Responsibility is, therefore, close to impossible since the actions of one State is difficult to untangle from that of others.[11] After all, all States contribute, more or less, to climate change and the triggering of ‘tipping points’. In this regard, Article 47 of ARSIWA may provide some guidance:

‘Where several States are responsible for the same internationally wrongful act, the responsibility of each State may be invoked in relation to that act.’

Recalling that the link between anthropogenic emissions and climate change is scientifically established, and against the background that some States, for instance, the US and China, are the biggest GHG emitters, one may be able to conclude that those States ought to incur the most significant proportion of responsibility for harms caused by GHG emissions.[12] However, strict and specific causation requires evidence of a nexus between a specific State’s GHG emissions and a specific harm, a task close to impossible for the complainant State to prove. The requirement of strict causation under the Law of State Responsibility acts as a block to finding States responsible for harms caused due to their GHG emissions.

The Convenience of the Current Law for States

As echoed by Principle 22 of Stockholm; and case law, as well as inherent in the concept of justice itself, there must be some compensation for harms caused. There are two significant issues in this regard. Firstly, climate change is unique in that a victim might as well be a wrong-doer in the sense that climate change is caused by the collective actions of all States,[13] which prompts the question of who is entitled to compensation. Accordingly, it is questionable how one might assess the appropriate compensation for irreversible damage, i.e. when the harm has reached the ‘point of no return’.

Nevertheless, what State practice seems to indicate is an unwillingness to set a precedent of utilising the Law of State Responsibility in regard to global concerns. For instance, after the Chernobyl accident, States were reluctant to claim compensation, although they had suffered significant harm due to the Soviet Union’s actions.[14] There may be political reasons behind the reluctance; after all, the USSR was not the only State using nuclear power, and the same is true for GHG emissions. Ultimately, all States could use such a precedent as potential ‘victims’, but it could also be used against them as potential ‘wrong-doers’. State practice instead suggests that although all States, sooner or later, will suffer the consequences, the preferable route in fighting climate change is to negotiate new treaty regimes rather than to bring certainty to the ambiguities of the Law of State Responsibility in the climate change context.[15] After all, they constitute a convenient barrier for States against responsibility for the harmful consequences of climate change.[16]

[1] Intergovernmental Panel on Climate Change (IPCC), ‘Climate Change 2022: Impacts, Adaptation and Vulnerability – Summary for Policy Makers’ (IPCC, no 6, 2022) 6.

[2] Intergovernmental Panel on Climate Change (IPCC), ‘Special Report: Global Warming of 1.5C’ (IPCC, 2018) 262.

[3] United Nations ‘‘Tipping point’ for climate action: Time’s running out to avoid catastrophic heating’ (, 16 September 2021) <> accessed 28 October 2022.

[4] United Nations ‘Climate change: No ‘credible pathway’ to 1.5C limit, UNEP warns’ (, 27 October 2022) <> accessed 28 October 2022.

[5] Responsibility of States for Internationally Wrongful Acts (2001) Yearbook of the International Law Commission, vol. II (Part Two) (ARSIWA) arts. 1; 2.

[6] See also: Scovazzi, T., ‘State Responsibility for Environmental Harm’ (2001) 12 Yearbook of International Environmental Law 43; Brunnée, J., ‘Of Sense and Sensibility: Reflections on International Liability Regimes as Tools for Environmental Protection’ (2004) 53 International and Comparative Law Quarterly 351.

[7] ibid.

[8] See also: Glickenhaus, J.C., ‘Potential ICJ Advisory Opinion: Duties to Prevent Transboundary Harm from GHG Emissions’ (2015) 22, N.Y.U. Environmental Law Journal 117.

[9] See also: Elena Evangelidis, ‘A chain as strong as its weakest link – climate science and legal causation after the Mozambique floods’ (Völkerrechtsblog, 11 September 2019) <> accessed 25 October 2022.

[10] See also: Voigt, C., ‘State Responsibility for Climate Change Damages’ (2008) 77, Nordic Journal of International Law, 1-2.

[11] See also: Tom Sparks, ‘Judging climate change obligations: Can the World Court rise to the occasion?’ (Völkerrechtsblog, 30 April 2020) <> accessed 25 October 2022.

[12] See also: Scovazzi, T., ‘State Responsibility for Environmental Harm’ (2001) 12 Yearbook of International Environmental Law 43.

[13] See also: Scovazzi, T., ‘State Responsibility for Environmental Harm’ (2001) 12 Yearbook of International Environmental Law 43

[14] See also: Voigt, C., ‘State Responsibility for Climate Change Damages’ (2008) 77, Nordic Journal of International Law, 1-2.

[15] See also: Brunnée, J., ‘Of Sense and Sensibility: Reflections on International Liability Regimes as Tools for Environmental Protection’ (2004) 53 International and Comparative Law Quarterly 351.

[16] ibid.