Can the Paris Agreement Help Climate Change Litigation and Vice Versa?

Abstract Domestic climate change litigation is prospering across the globe to the extent of becoming a transnational phenomenon of growing importance. At the international level the Paris Agreement, although still in its infancy, has been established as the core element of the climate change governance framework. This article explores the still opaque relationship between domestic climate change litigation and the Paris Agreement. It is argued that dynamic interaction between domestic litigation and the Paris Agreement may improve the overall efficacy of both regimes. On the one hand, an examination of the Paris Agreement's architecture and provisions reveals pathways that are already being used or can be explored further in litigation. On the other hand, litigation can assist and complement the Paris Agreement with regard to its implementation and progress towards its overall goals. The result may deliver more than a multi-level perspective on climate change law. As it captures the law in action on different levels, the proposed ‘cross-level’ approach has due regard to the implications of the mutual supportiveness or complementarity of legal tools. It also thereby responds to the concern of whether the law can be of significant benefit in addressing complex global issues like climate change.


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The question of whether the conclusion of the Paris Agreement, 1 a treaty under international law, is a sufficient assurance that standards in climate change mitigation or adaptation will in fact be implemented, monitored, and enforced has been widely debated. Doubts may be rooted in, for example, the non-binding character and discretionary formulation of many of the Agreement's provisions or the lack of political commitment in respect of its implementation and enforcement. 2 It is certainly true that the effectiveness of the Paris Agreement depends on the choice, design, and enforcement of substantive measures taken at the national level. This is notwithstanding a sophisticated international transparency and accountability framework, and parallel consideration of certain binding and non-binding international standards. At domestic levels, climate change litigation is prospering across the globe to the extent of becoming a globally visible transnational phenomenon of growing importance. Within the last decade, adjudication and liability in climate change matters has transcended the academic realm and gained a foothold in contemporary practice across numerous jurisdictions. 3 Consequently, litigation has become a transnational feature of climate change governance. 4 This domestic litigation in the era of the Paris Agreement may open up a different perspective on climate change lawone that is 'cross-level' rather than international and national, focuses on interactions rather than the legal normativity of single instruments, and seeks to identify possible synergies between international and domestic lawmaking and adjudication.
Against this background, this article explores the still opaque relationship between the Paris Agreement and domestic climate change litigation in its manifold shapes and domestic coinages, both conceived as legal tools for effective climate change mitigation and adaptation. Taking an instrumental approach, the hypothesis is that these tools are indeed mutually integrable: the goals, the architecture based on nationally determined contributions (NDCs), transparency standards and oversight mechanisms of the Paris Agreement, and the review of climate change-related domestic measures in national courts may functionally interact, thus contributing to the efficacy of climate change governance.
For this purpose, firstly, this article will explore the discernible domestic turn within the current international framework of climate change law and governance and its reflection in domestic litigation. Secondly, it will examine how the objectives and provisions of the Paris Agreement may be operationalized and harnessed in domestic climate change litigation. The focus here is directed towards national courts as the fora for the 2 Cf., e.g., D. Bodansky Ten years ago, litigation beyond technical issues relating to climate change was more of a theoretical possibility than a feasible strategy: see, e.g., J. Gupta Ibid., p. 76 (describing a governance framework comprising a 'growing set of symmetric and asymmetric concentric circles of governance, where even actions that are seen as ostensibly independent are either rooted in, or develop in reaction to, the core governance framework. At the core of this governance framework is the United Nations Framework Convention on Climate Change (UNFCCC), its Kyoto Protocol and the numerous decisions of the UNFCCC Conference of the Parties'). Elaborating further on the transnational governance potential of climate change litigation, see also J. Peel  adjudication of actions of mitigation and adaptation, which under the Agreement's architecture must be determined and conducted at the national level. 5 Primarily, it will look at how the Paris Agreement helps litigation in holding states responsible for adopting and implementing mitigation action. The article will then analyze how domestic climate change litigation may improve the efficacy of the Agreement. The article will conclude that, besides opening an interesting perspective on the relevance of legal instruments, the interaction between the Paris Agreement and domestic litigation is better suited than any singular regulation to achieve effective climate change mitigation and adaptation. Domestic climate change litigation plays a particularly important role in maintaining and strengthening these linkages. formulates an internationally agreed collective goal, 11 but it relies on the national determination of individual contributions to mitigation and adaptation; 12 institutionalized compliance review is limited and is equipped only with a facilitative non-compliance procedure; 13 and parties' actions entail no liability established under the treaty itself with regard to loss and damage. 14 On the other hand, there is a high degree of detail for procedural obligations and a sophisticated 'ratcheting mechanism' that is designed to influence individual states' decision making. 15 This mechanism is accompanied by a high standard of transparency established by the Paris Agreement. 16 Parties are also required to harmonize their NDCs and are expected to cooperate in implementation of mitigation and adaptation measures. 17 Therefore, decision making is not left to the unlimited discretion of each state; collective goals, international standards, and transnational processes are established to guide individual efforts. In assessing the Agreement, we have to look at it from a different perspective from that of assessing a specific, rule-based law. The Paris Agreement manifestly focuses on the management of cooperation, administration of the various national efforts, and generation of review processes in view of a collective goal. Thus, normative and functional interlinkages and interactions between the international and the national levels may be of particular relevance.

Domestic Climate Change Litigation: A Global but Multifaceted Phenomenon
Political institutions have been and probably will continue to be the dominant actors in the field of climate change, at both the international and national levels. Over the last two decades, however, the role of judicial organs and, in particular, domestic courts has evolved significantly. 18 The database on climate change litigation maintained by the Grantham Research Institute and the Sabin Center bears testimony to this. 19 Relatively recent casessuch as Leghari v. Federation of Pakistan in Pakistan 20 and 11 See Art. 2(1) Paris Agreement. 12 Cf. Arts 3, 4(2) and 7 Paris Agreement. 13 Cf. Art. 15(1)-(2) Paris Agreement. 14 17 Harmonization at least to an extent that allows comparability: cf. Arts 4(8), 6(1) and 7(6)-(7) Paris Agreement. 18 See the overview of the first significant developments in the field of international environmental law in general from D. Bodansky 23 Climate change litigation has evolved from a few cases in a handful of countries in the years following the conclusion of the Kyoto Protocol 24 to a wave of cases as the era of the Paris Agreement begins. 25 While climate change litigation, as such, is not a new phenomenonit has been around at least since the mid-2000s, especially in the United States (US) 26 early efforts were often unsuccessful in convincing courts of a legally relevant failure of state climate policies. 27 Currently, many climate change cases address mitigation policy in a more comprehensive way, for example, by requiring more ambitious overall targets. 28 Cases are also more broadly distributed across the globe. 29 Interestingly, one can observe a turn to human rights-based arguments and remedies. 30 Several recent and ongoing cases illustrate that courts may have become more receptive to the relevance of human rights for state actions in this context. 31 It may be favourable to this development that the role of national courts in human rights implementation and enforcement appears to be better established than is judicial intervention on the basis of principles of environmental protection. 32 Joyeeta Gupta's hypothesis from the earlier phase of climate change litigation gives an initial perspective on heterogeneity and harmonization among cases: [T]ransnational epistemic communities of legal scholars and lawyers may promote legal principles and concepts simultaneously at the national and international level through legal scholarship and the use of litigation and [such] promotion may lead to similar court judgments in national courts in different parts of the world using similar principles, doctrines and often referring to case law in other countries. 33 While similar patterns and even explicit cross-references can be seen among cases in different jurisdictions, 34 climate change litigation still remains a heterogeneous phenomenon. 35 Litigation in the area of climate change is based ultimately on national legal conditions. While cases like the German Lliuya v. RWE 36 do not involve state actors, have a specific legal basis and aim to provide a remedy for climate change damage, litigation such as in the case concerning deforestation in the Colombian 28 Cf. the cases listed at n. 23  Amazon 37 or in Juliana v. United States of America 38 does involve state actors, is based on rather broader legal concepts, and aims to create or enforce obligations to take preventive action. As the analysis here aims to provide a better understanding of the (potential) interaction between the Paris Agreement and domestic litigation, cases that deal with isolated aspects of domestic regulation, without any relevant connection with the international governance of climate change, will be set aside. Instead, a particular focus will rest on litigation that aims to review climate action or climate-relevant activities in light of international developments. 39

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The observations made in Section 2 may raise the questions of whether and, if so, to what extent recent developments in litigation can be linked to the contemporary international climate change regime. Because domestic and constitutional sources have a more direct legal impact on litigation 40 the legal value of the Paris Agreement may easily be neglected. Its mechanisms and norms, as will be outlined, are indeed rarely directly justiciable in national proceedings. However, these norms and mechanisms do find their way into domestic climate change jurisprudence as a means of interpretation and guidance, as well as significant indirect drivers of litigation itself. The analysis in this section of observed and potential effects of the Paris Agreement on climate change litigation concludes that, in particular, the ambitious goals of the present international climate change regime, states' NDCs and the mandatory updating can be highly valuable inputs into domestic litigation.
In order to assess the effects of the Paris Agreement, the relevant articles and their legal design will be outlined with a view to linking international and domestic climate law and policy. The goal of the Paris Agreement is to hold the global temperature rise to 'well below' 2°C in comparison with pre-industrial levels and to make efforts to limit it to 1.5°C (Article 2(1)(a)). Parties' efforts, such as those declared in NDCs, must be oriented towards this goal. 41 With regard to this goal, parties are expected to reach a global peaking of greenhouse gas (GHG) emissions as quickly as possible (Article 4(1)).
Parties have agreed to achieve a rapid reduction in emissions with the aim of positive and negative emissions being balanced in the second half of the century. This aim is more specific but less demanding than the overall goal of Article 2(1)(a) as the overall goal could potentially imply that this balance must be achieved even earlier. 42 In view of the preamble to the Paris Agreement and its adoption 'under the Convention', 43 these goals must be read together with the 'ultimate objective' in Article 2 UNFCCC. 44 This integrated interpretation of the goals of the international climate change regime, which is consistent with the precautionary approach, suggests ambitious action in light of established scientific findings. 45 The Paris Agreement goals are highly relevant for domestic lawmaking and judicial interpretation, even if they are not themselves justiciable. The Agreement's temperature goal contains strong language of legal effect, leaving no discretion for parties to follow divergent temperature goals. Domestic efforts will need to be oriented towards this goal, which requirement has been translated into a global emissions budget. 46 However, as parties have intentionally neither agreed on national budgets nor on respective methods of calculation, individual carbon budgets and respective national targets are to be set by national policy or law. Still, in view of the provisions on common but differentiated responsibilities and respective capabilities (CBDR-RC) (for example, in Article 4(4) of the Paris Agreement) or on the basis of alternative principles of burden sharing among states, courts can derive further guidance for an assessment of the adequacy of envisaged or actual national contributions. 47 41 Art. 3 states: 'with a view to achieving the purpose of this Agreement as set out in Article 2'. 42 See also, with regard to potential conflict between the goals, F.  46 The IPCC is following the global carbon budget approach, e.g., in the IPCC Special Report, ibid. 47 Whether they will do so will also depend on whether litigants expressly articulate the principle in domestic proceedings, concludes P. Galvão

Impact on litigation
In cases where international climate change law has been invoked, it has generally been applied indirectly, as a means of interpretation or guidance, rather than serving as a direct legal basis. 48 It is a constitutional requirement in many countries to interpret national law, to the extent possible, in conformity with international law. 49  several pending cases, recourse is taken to the overall goals to support particular interpretations of climate-related provisions in national or supranational law and thus call for more ambitious domestic mitigation targets. 55 While helping to synchronize domestic targets with the ambitious and dynamic character of the overall objectives under the Paris Agreement and the UNFCCC, domestic courts may play an important role in defining and reducing executive or legislative discretion in view of evolving science and evolving international agreement. Considering the goal in Article 2(1)(a) of the Paris Agreement and the recent Intergovernmental Panel on Climate Change (IPCC) Special Report on the 1.5°C goal, 56 it may be possible to cut the scope for manoeuvre drastically. 57 The report, in any case, strengthens legal arguments based on human rights and on a failure to observe a duty of care as a result of the stronger and more comprehensive scientific evidence of the nexus between climate change and human rights presented in the report. 58 As mentioned in the previous section, the IPCC has calculated a global carbon budget in accordance with the goals set under the Paris Agreement. This global carbon budget approach was relied on by the court in Gloucester Resources Ltd v. Minister for Planning to uphold the refusal of a company's application to construct a coal mine. 59 Beyond that, litigants in Carvalho and Others v. Parliament and Council have argued that the Paris Agreement's temperature goal and burden-sharing principles allow for deriving a carbon budget applicable to the European Union (EU) in order to assess the adequacy of envisaged emissions reduction levels. 60 In another case, litigants argue that the global carbon budget approach may be used in relation to national longterm targets in order to identify an 'over-emission' and consequently a violation of selfcommitment. 61 While these approaches clearly indicate that the internationally agreed temperature goal can be framed and deployed in legal arguments, there are limits. In the absence of specific rules to determine individual shares of the global carbon budget, national courts will have difficulty in deciding the specific extent to which the 55 See, e.g., Carvalho and Others v. Parliament and Council, n. 23 above; the same applies to most of the cases listed in n. 23 above. 56 IPCC Special Report, n. 45 above. 57 Although parties have been cautious in approving the specific findings and the urgency expressed in the IPCC Special Report (n. 45 above), the guiding function of the IPCC reports reflecting 'best available science' has been acknowledged: see Decision 1/CP. 24 The normative architecture of the Paris Agreement is essentially shaped by the features of NDCs, transparency and oversight, and 'ratcheting mechanisms'. The 'hinge-provision' of Article 3 ties the overall goal of the Paris Agreement to an obligation upon the signatory countries stipulated in Article 4(2) to set up, communicate, and uphold NDCs, which must be implemented by respective measures. Although Article 3 extends the establishment of NDCs to the areas of adaptation, finance, technology, capacity building, and transparency, Article 4 contains specific obligations and standards that apply only to the area of mitigation. The obligations with regard to mitigation are therefore significantly more detailed and strict than those concerning NDCs in adaptation or finance. 67 In terms of NDCs, substantive and procedural requirements set in the Paris Agreement, the content of NDCs, and their legal nature could be of relevance to domestic litigation.
Substantive requirements in Article 4, such as those concerning the implementation of measures, leave significant scope for national discretion ('shall pursue domestic mitigation measures, with the aim of achieving the objectives of such contributions'). 68 Still, Article 4(2) establishes an expectation of good faith 69 and arguably introduces a standard that guides the assessment of domestic measures to implement NDCs. 70 Such a non-binding expectation also exists with regard to the gradual tightening of NDCs, 71 and with regard to the reflection of the highest possible ambition of the party in its self-determined targets (Article 4(3), in concretization of Article 3). However, significant discretion is left to governments in determining what constitutes the 'highest possible ambition' in light of national circumstances. Further, developed country parties should set up economy-wide binding targets in view of their CBDR-RC (Article 4(4)). In the Paris Rulebook, parties have agreed to clarify how these standards and expectations have been addressed in the determination of NDCs. 72 In sum, although substantive requirements create a normative guideline for states to follow in preparing their NDCs, they do not provide a template for the substantive content of NDCs because of their non-binding and discretionary character.
Procedural requirements, on the other hand, have more direct influence on the preparation of NDCs. The requirement in Article 4(2) to set up, communicate, and uphold NDCs is a legally binding and justiciable obligation of states. 73 The required detail of information in order to allow tracking of collective and individual progress is determined in Articles 4(8) and 13(7), and specified in the Paris Rulebook. 74 To strike a balance between international guidance and national discretion, parties have agreed that shared information needs to be quantifiable and detailed, and substantiate ambition in view of the overall goal, the global stocktake, and national circumstances. 75 Information has to be updated regularly and must be particularly detailed with regard to national implementation. 76 The dynamic of regular updating is reinforced by the periodic global stocktake on collective progress in realization of the overall goals (Article 14) that will inform parties in setting their NDCs and connects to the 'ratcheting mechanism'. 77 This mechanism to produce ambitious national contributions has the following elements: (i) the clear indication of a pathway (goals and objectives); (ii) the five-year period of renewing NDCs; and (iii) the requirement of their gradual elevation and periodic review. 78 The procedural requirements regarding NDCs, therefore, primarily produce a significant source of information and dynamic in the decision-making process, as national measures and international standards are under constant review and adjustment. As such, they are not only crucial in holding states accountable for their NDCs at the international level, 79 but can simultaneously affect the domestic level, particularly review processes, by providing necessary substance and impetus for domestic litigation.
Considering the actual content of current NDCs, 80 targets are set in very different ways and there is a lack of information on methodologies for emissions projections, resulting in challenges for the assessment of implementation. 81 This is expected to improve with the implementation of the Paris Rulebook. 82 Another discernible deficit in current NDCs is a lack of information or detail regarding the linkage of individual efforts and collective goals, 83 contrasting the emphasis of this linkage in Article 3 of the Paris Agreement.
Another issue of relevance for invoking NDCs in domestic judicial proceedings concerns their legal nature. NDCs reflect mostly political outcomes or action plans adopted at the national level. 84 Although they do represent a certain commitment towards specified action, they do not necessarily reflect domestic law or legislation. For this reason, it matters whether the international legal nature of NDCs is assumed to be binding or not, 85 and whether they have direct effect in the domestic legal order or not. As a source of international legal obligations NDCs could be invoked directly or as means of interpretation. If NDCs are not assumed to be legally binding within the domestic order it is legally conceivable for NDCs and implemented measures to diverge without this opening up the possibility of bringing justiciable domestic claims on the basis of the content of the NDCs. This would be different when legislation and NDCs are sufficiently synchronous. 86 In that case, the content of NDCs as enshrined in national legislation is legally binding, and could be invoked to demonstrate the (in)adequacy of national implementation measures.
In addition to the development of NDCs, Article 4(19) recommends that parties should develop and publish national long-term strategies for low GHG emissions development. Although this provision is not legally binding, several parties have already made use of it. 87 The national long-term strategies generated by this mechanism can play a crucial role in linking domestic short-term action to the overall mitigation goals. 88

Impact on litigation
The justiciability of national targets set by executive or legislative action is a major issue in domestic litigation. 89 Domestic targets could be invoked either in the form of NDCs or as national political or legal instruments. In the judgment of the Colombian Supreme Court in Future Generations v. Ministry of the Environment and Others, the country's pledge to stop deforestation, as included in its NDC, 90 is considered to be a binding commitment of the state. 91 In contrast, the court in Thomson v. Minister for Climate Change Issues clearly considered NDCs to be non-binding on states and therefore not relevant for the court's decision. 92 In Earthlife Africa Johannesburg the court relied on NDCs but did not state clearly whether their content is binding on the state or not. 93 However, not only the content of NDCs may have an impact on domestic litigation. In particular, procedural obligations regarding the preparation of NDCs and the nonbinding provision on long-term strategies (Article 4(19)) produce impetus and input for litigation. Having recourse to Germany's long-term Climate Action Plan 2050 94 and its short-term targets, and linking them with the overall temperature goal of the Paris Agreement, applicants in Family Farmers and Greenpeace Germany v. Germany argued, inter alia, that by exceeding the national carbon budget, the country violates its self-imposed and legally binding objective. 95 Owing mainly to transparency requirements of action and targets under the Paris Agreement, non-governmental organizations (NGOs) and even individuals are empowered in the sense of being able to monitor state behaviour and take political or legal action to trigger implementation or enforcement processes. 96 Further value of a high standard of transparency and reporting obligations is exemplified by the Urgenda case before Dutch courts. In order to establish that the Dutch government had not observed the required duty of care, Urgenda and the other plaintiffs relied essentially on the transparency of government action, in combination with its consent to ambitious targets at the international level. 97 The obligation to provide information necessary for the review of progress made in implementing the NDCs under Article 13(7) will potentially allow for further judicial assessment of the implementation of NDCs in view of the goals of the Paris Agreement.
Moreover, domestic courts are generally receptive to following the guidance of standards agreed in the Paris Agreement and apply them to national law. Although not based upon Article 4 of the Paris Agreement, 98 according to an interpretation of national legislation consistent with the Agreement, the court in Thomson v. Minister for Climate Change Issues considers that the review of mitigation targets in light of new best available scientific information 'is a mandatory relevant consideration' under domestic law. 99

Narratives of Human Rights and Loss and Damage
In a less direct way than the normative architecture of NDCs, transparency and oversight, and ratcheting requirements, the Paris Agreement's references to human rights in the preamble and to loss and damage in Article 8 may also contribute to further litigation. 100 Although the Paris Rulebook did not ultimately include the requirement of information on measures to safeguard human rights in NDCs, 101 the 'people and impact'-centred notion of the preamble links the obligations and efforts of states to potentially affected individual legal positions, thereby implicitly promoting access to review of impacts on the individual under existing rights mechanisms. These rights 96  mechanisms do not necessarily have to be international institutions. For example, the comprehensive investigation of the Commission on Human Rights of the Philippines concerning the link between the activities of so-called carbon majors and individual human rights illustrates the involvement of (quasi-)judicial organs at the national level. 102 Also, in more adversarial proceedings domestic courts appear to be more receptive to rights-based arguments. 103 The 2018 Court of Appeal decision in the prominent Urgenda case illustrates this turn. While the court of first instance had relied on constitutional principles and the doctrine of hazardous negligence in Dutch civil law, 104 the Court of Appeal had recourse to the duty to guarantee the rights under Articles 2 and 8 of the European Convention for the Protection of Human Rights and Fundamental Freedoms (ECHR) 105 and accordingly required the state to take concrete actions to prevent a future violation of protected individual interests. 106

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Another interesting issue from the legal perspective is the regulatory significance of climate change litigation. Do climate change cases before national courts complement the international legal framework or serve as 'stop-gaps' for legislative failure in international law or national law? The aim of this section is to provide an overview of the functions and limits of litigation in influencing the effectiveness of the international climate change regime.
In the field of climate change, litigation before domestic courts can supplement the framework under the Paris Agreement in various ways: it can enhance progress towards the regime's collective goals, it can trigger or support internalization processes, 107 and it addresses aspects that are envisaged by the Paris Agreement but cannot be realized in the international arena. More generally, litigation can help to maintain the link between international standards under the climate change regime and domestic policy and law, thereby contributing to the harmonization of international and national standards and approaches across the world. 108

Stop-Gap or Complement?
A principal function of strategic litigation is to respond to governance gaps in the forms of inadequate lawmaking and enforcement by governments. 109 With regard to climate change, the long quest for the adoption of a treaty to succeed the Kyoto Protocol has inspired innovative solutions at levels other than the international and within institutions other than the UNFCCC bodies. While in the immediate aftermath of the Kyoto Protocol, at the national level many countries were concerned with implementation in the face of more apparent deficits of the Agreement regarding participation and insufficient ambition of mitigation commitments, litigation hasalbeit in isolated casesassumed the function of a 'stop-gap' in order to provide impetus for addressing climate change. 110 The Urgenda case illustrates that regulatory failure in the face of an insufficient second commitment under the Kyoto Protocol 111 gave rise to domestic litigation aimed at aligning domestic policy with the progress of knowledge regarding the urgency of the problem and recent agreements at the international level. The approach can be broad and require fundamental legislative action, 112 or narrow when specific adjustments of governance instruments are called for. 113 Cases can shape government decision making and legislation beyond merely providing 'stop-gaps'. 114 Some courts have ruled on the establishment of dynamic institutions or processes to help further implementation as well as policy development. Examples are the establishment of a Climate Change Commission, and later a Standing Committee on Climate Change, in the Leghari case, 115 and the requirement to establish an Intergenerational Covenant for the Life of the Colombian Amazon in the case before the Supreme Court of Colombia. 116 In this manner, the Paris Agreement creates new opportunities for litigation to create complementary governance tools.

Approximating the Overall Goal, Enhancing Internalization, and Addressing Shortcomings
A shortcoming in the architecture of the Paris Agreement consists of the loose legal links between the collective overall goal, and individual efforts. 117 Existing NDCs are insufficient, 118 and some worry that parties may not be adequately incentivized to step up with regard to their NDCs and follow-up after the review process. 119 'Ratcheting mechanisms' at the international level are designed as a surrogate for a stronger legal obligation to adjust NDCs to the overall goal. A facilitative procedure to 'promote compliance with the provisions of the Agreement' (Article 15) is in place to contribute to that aim. However, there is no mandate to review the adequacy of an individual NDC, or the tightening of subsequent NDCs in relation to earlier versions. 120 National court decisions can provide an effective incentive and thus complement the ratcheting mechanisms. This does not necessarily require courts to follow the applicants' reasoning and compel governments to adjust their individual efforts in line with a collective temperature goal. 121 Litigation as such can create ratcheting effects by raising public awareness and mobilizing NGOs to challenge climate policy, and by providing impetus for government review of the adequacy of targets or measures. 122 Even if courts reject stricter mitigation targets on grounds of governmental discretion, to direct awareness to a possible disconnection between such targets and the goals of the Paris Agreement in light of best available science can already contribute to better streamlining. While, at the international policy level, consideration of IPCC reports may face certain political constraints, 123 cases that involve an alleged disconnection force states to engage with these reports and their implications for national targets at the domestic level. 124 In this sense, domestic litigation is able to create a meaningful link between science and climate policy that is worthy of more detailed discussion. This discussion, however, is beyond the scope of the current article. With regard to substantive norms of international law, it has been argued that they are heavily dependent on implementation by national courts and are likely to remain a 'dead letter' until applied to a case at hand by national judges. 125 In general, national courts have also been seen to further the implementation of international environmental law by applying it to an individual case, by creating a deterrent effect, and by incorporating international norms and standards into domestic law. 126 Although the Paris Agreement does not contain substantive provisions comparable with the mitigation provisions of the Kyoto Protocol, it nonetheless sets up a normative architecture of internationally agreed standards and expectations. These are in need of translation into domestic governance and, finally, domestic action. While this may be primarily a task for legislatures, domestic courts can contribute by 'holding their governments to account, and … ensuring that … commitments are given practical and enforceable effect'. 127 Rather abstract provisions, such as the collective temperature goal, which are not directly justiciable, are given practical effect when invoked in domestic courts. 128 In a similar way, litigation can complement the more political 'naming and shaming' mechanism resulting particularly from the transparency framework. The transparency framework's latent enforcement potential can thus partially be fulfilled in legal proceedings. 129 Moreover, by referring to the non-binding standards set by the Paris Agreement and NDCs, national courts help to strengthen the legitimacy of those standards.
In addition to the potentially deterrent function of domestic litigation in the absence of an effective compliance mechanism at the international level, 130 domestic litigation may address another shortcoming of the Paris Agreement. Although the Agreement has enshrined the Warsaw International Mechanism on Loss and Damage in Article 8, it has explicitly refrained from providing a basis for liability and compensation. 131 In this regard domestic climate change litigation can serve partly as a complementary tool. Obligations concerning the restitution of damages, not only of states but also of private actors, which cannot be established by international law, can be determined in domestic courts and connected with the governance framework of climate change.

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This article adds to the discussion about the efficacy of the Paris Agreement. On the surface, the managerial aspects of the Agreement may well reveal nothing more than a few legally binding obligations with only a moderate compliance pull. When viewed from the standpoint of domestic litigation, international climate change law may suddenly appear much more effective. Therefore, the theoretical question of whether the law can respond to complex issues like climate change perhaps also must be answered by viewing the law in action at different levels and having due regard for 'cross-level' interlinkages. This perspective corresponds to the idea of a central but limited role of international law, whereby it provides an integrating value system and a framework for action and monitoring. 132 Climate change litigation, however, does not replace the accountability and ratcheting mechanisms established at the international level. It rather adds a complementary, multifaceted second mechanism which allows for the direct involvement of non-governmental actors.
As a review of climate policy at the national level is likely to spill over directly to the international levelmostly as a result of the NDC architecturean accessible and efficacious court review of such policy further benefits the participation of civil society: it connects the right of access to justice with public participation in decision making in climate matters at national and international levels and thus provides an additional role for private actors in the governance framework. Thus, it complements the nonstate actor mobilization as envisaged by Article 6(4) and (8) of the Paris Agreement. 133 As a central element of climate change governance, NDCs are likely to become more relevant for the international and the domestic accountability mechanisms with the implementation of the Paris Rulebook. 134 At the domestic level, this would provide further impetus for litigation aimed at assisting or directing political institutions to synchronize individual contributions with the overall goals of the Paris Agreement. 135 A significant share of the problem in achieving effective mitigation of climate change lies in the fact that earlier international instruments failed to produce ambitious substantive domestic action on a global scale. A look at the evolution of the regime reveals that the problem has been at least as much related to the question of dynamic and adequate adjustment of goals as it has been related to the question of the 'bindingness' of international instruments. Domestic climate change litigation may be only part of the solution but, as a legal tool, it has significantly more potential under the truly global Paris Agreement than under its predecessor, the Kyoto Protocol: enhanced 'cross-level' interaction enables domestic litigation to play a significant role in ratcheting up ambition in climate change mitigation efforts and enhancing the internalization of internationally agreed standards.