Legal standards for judging States’ mitigation efforts

by Lucy Maxwell, Sarah Mead and Dennis van Berkel

Climate litigation occurs against a backdrop of climate crisis and government inaction. As this GNHRE blog post series explains, communities are increasingly turning to the courts as a last resort to compel high-emitting countries to ramp up their mitigation ambition. Following the landmark Urgenda case in the Netherlands, these ‘systemic mitigation’ lawsuits – which seek to compel a State to increase its overall mitigation efforts – have spread to every corner of the world.

Several judgments of national courts have led to significant increases in governments’ efforts to reduce greenhouse gas (GHG) emissions, including in France, Ireland and Germany. Such cases have huge potential to close the yawning ‘emissions gap’ and hold global average temperature increase below the danger line of 1.5°C above pre-industrial levels.

Yet, these cases can pose challenges for judges, with some national courts expressing concern about a perceived lack of standards against which to assess the legality of a State’s mitigation efforts.

In response to these concerns, we have set out the lessons that can (and should) be taken from recent cases in this article of the Special Issue. Specifically, we identify a set of standards for judging a State’s mitigation efforts, drawing on international environmental law, best available science and recent advancements in quantifying a country’s ‘fair share’ of emission reductions.

We indicate how national courts have used these standards in cases to date, and identify future directions for the adjudication of systemic mitigation cases. While the legal contexts of climate cases differ, we believe that these standards can be applied across jurisdictions, including those in which climate litigation has thus far been less successful.

Most systemic mitigation cases are premised on a State’s obligations under human rights law or tort law (but may also be based on public law). These cases utilise well-established rules which oblige a State (or its organs) to adopt ‘reasonable’ measures to prevent or minimise a foreseeable and serious risk of harm to persons or things within its jurisdiction. As a general rule, the test for breach of this obligation is whether the State has met a minimum standard of reasonableness in devising its response to the risk of harm.

The question is: how does this legal obligation apply in the context of climate change?

Judgments rendered in systemic mitigation cases thus far show two key developments.

First, most courts have recognised the justiciability of systemic mitigation cases – an important threshold issue. This includes the courts in the cases mentioned above, as well as in Belgium, Canada, Colombia, and Nepal. Some unsuccessful cases in North America (see e.g. here and here) are an anomaly in this respect.  

Secondly, many courts have recognised that the State has a legal duty under existing human rights and/or tort law to undertake mitigation efforts (through GHG emissions reduction) in light of the current and projected harm caused by climate change. Crucially, these judgments establish that the State’s duty exists notwithstanding that climate change is a global problem, which cannot be solved by any individual country. This includes decisions of courts in the Netherlands, Germany, France, Belgium, Nepal and Colombia, in the cases referred to above.

The Dutch Supreme Court in Urgenda v. the Netherlands,for instance, determined that the State must do “its part” in order to prevent dangerous climate change, and expressly rejected the State’s defence that its emissions were negligible in absolute terms.

Fewer courts, however, have proceeded to assess whether a State’s overall mitigation efforts are sufficient to discharge its legal obligations. In most instances, courts have upheld the plaintiffs’ claims on grounds that do not require an assessment of the reasonableness of the State’s efforts, or have determined that a State has such a wide margin of discretion in this context that the alleged violation of obligations in human rights law or tort law is unfounded.

Nevertheless, lessons for future cases can be drawn from decisions of courts that have taken this step, including the judgments from the Netherlands in Urgenda and Germany in Neubauer et al v. Germany.

These judgments show that courts can identify concrete standards against which to assess States’ mitigation efforts when existing duties in human rights law and/or tort law are interpreted in light of international law and best available science. What follows is a summary of these standards, each of which is expanded upon in our article.

In order to discharge its legal obligations to take reasonable measures to protect persons or things within its jurisdiction from the foreseeable and severe harm posed by climate change, a State must adopt measures to mitigate climate change by reducing its greenhouse gas (GHG) emissions.

Such mitigation measures should:
(a) be based on a long-term temperature goal of at least 1.5°C;
(b) be informed by the principles of equity and common but differentiated responsibilities, on the basis of which each country needs to do its ‘fair share’ as informed by best available science;
(c) include a date by which to achieve carbon neutrality, which for developed countries should be well before 2050;
(d) be internally consistent (that is, short-term mitigation measures should be scientifically consistent with long-term mitigation measures);
(e) represent a ‘progression over time’, with regular increases in ambition;
(f) not rely excessively on negative emissions technology; and
(g) be sufficiently detailed to indicate how emissions reductions will be achieved.

National courts have already recognised that these indicators provide a basis against which to assess the reasonableness of a State’s measures, as we outline in our article.

For example, several national courts have recognised that mitigation measures should be premised on a long-term temperature goal of 1.5°C, including in Milieudefensie v Royal Dutch Shell (2021), Friends of the Irish Environment v Ireland (2020) and Urgenda v. Netherlands (2019). States themselves recently reaffirmed that 1.5°C is the danger line in the Glasgow Climate Pact, which was unanimously adopted during COP26 in November 2021.

National courts have also increasingly engaged with standards for assessing a country’s ‘fair share’ of the global emissions reduction burden – an issue at the centre of systemic mitigation cases. The Urgenda case represented the first time that a court tackled this question. The Supreme Court of the Netherlands highlighted that the Dutch State had committed, as a developed country party to the UN Framework Convention on Climate Change, to ‘take the lead’ in emissions reduction, and to do so in line with the principles of equity and common but differentiated responsibilities (CBDR-RC).

To ascertain what this obligation meant in practice, the Supreme Court drew on findings in the IPCC’s Fourth Assessment Report (AR4), which concluded that developed countries needed to reduce their emissions within a range of between 25 to 40% by 2020 compared to 1990 levels. The court accepted the opinion of its independent legal advisors that – while this finding was not binding on the court as such and didn’t provide “cut and dried answers” to the question of ‘fair share’ – it was a “reasoned proposal”. The emissions reduction range was derived from the latest scientific studies and covered a broad spectrum of effort-sharing methodologies, and could therefore be taken as a starting point for specifying the duty of care of the Dutch State.

The German Constitutional Court in Neubauer took a similar approach. While acknowledging that there existed various methods for determining a State’s necessary emissions reductions (all of which entailed uncertainties), the Court found that:

“… this does not make it permissible under constitutional law for Germany’s required contribution to be chosen arbitrarily. Nor can a specific constitutional obligation to reduce CO2 emissions be invalidated by simply arguing that Germany’s share of the reduction burden and of the global CO2 budget are impossible to determine.”

We see a similar approach in the Shell decision of the Hague District Court, concerning a company’s climate mitigation obligations pursuant to tort law. The court accepted that while “no one single [reduction] pathway is the measure of all things on a global scale”, there nevertheless exists “widely endorsed consensus” regarding the minimum emissions reductions that are required to avert dangerous climate change.

These decisions show that, notwithstanding the absence of ‘hard’ answers, it is possible for courts to determine whether a State’s mitigation efforts fall outside of the range of its minimum ‘fair share’.

Going forward, there is a robust body of ‘effort sharing’ literature that courts can draw upon to assess this question of ‘fair share’. This literature, which was similarly relied on by the IPCC in AR4, uses scientific methodologies to divide the remaining emissions ‘space’ or budget between countries. A prominent publication by Rajamani et. al. applies these methodologies in light of principles of international law, making it especially important for climate litigation. The study concludes that in order for developed counties to contribute to the global effort of emissions reduction, in line with international law and in particular the principles of equity and CBDR-RC, they must reduce their emissions to net-zero (and some become net-negative) by around 2030.

Even if courts are not willing to engage with this literature, there are still standards that they can use to assess States’ mitigation efforts in light of their legal obligations. At the most basic level, courts can consider the ‘global average’ of emissions reductions required to hold global temperature to 1.5°C. All States have accepted that developed counties need to ‘take the lead’ in reducing emissions (e.g. UNFCCC, Arts 3.1 and 4.2). Developed countries should, therefore, at the very least reduce GHG emissions at a greater rate than the ‘global average’ reduction rate for limiting global warming to 1.5℃ (which is a reduction of 45% by 2030 relative to 2010 levels, as recognised by States in the Glasgow Climate Pact).  

The climate crisis poses unprecedented challenges for humanity. The law will increasingly be called upon to hold governments (and corporations) accountable for their contribution to dangerous climate change. It is crucially important that litigators and courts use the tools at their disposal, including those provided by law and science, to scrutinise States’ mitigation efforts to ensure that they provide a real chance of holding global average temperatures below 1.5°C.