A new era of Anthropocene which replaced the Holocene era brought changes to stable system of international legal order. As Vidas, Zalasiewicz & Mark (2015) mentioned, '[t]he conditions of the Anthropocene will bring a fundamental shift in the context in which international law operates-a shift in which the challenges are increasingly recognized as the consequences of natural, not only political, change'. These changes are accelerated by climate change (CC)-a phenomenon which affects every aspect of human life. Climate change is an issue that cuts across many domains and at the same time the CC regime is fragmented into various functional and sector-specific areas (Boyd, 2014; Gaur & Squires, 2018; Oh, 2017). CC challenges demand high level of coordination and cooperation in different sectors of international and national law. At first blush, international environmental law may be recognized as best suited for this task, but it suffers lack of coherence itself, thus, more integrated approach is needed.
International environmental law has developed in a way that can be described as piecemeal and disaster-driven: the international environmental governance system consists of legally autonomous yet thematically kindred multilateral environmental agreements (MEAs), all of which have created their own institutional arrangements, approaches and rationales (Goeteyn, 2013; Garafova & Kichigin, 2016; Potoski, 2017). The risk of further fragmentation of the environmental governance system is rising, since the proliferation of the MEAs, both from thematic and institutional points of view, means there is a rising danger of overlap, double work and conflict between them (Goeteyn, 2013; Morrow, 2017 & 2017a). Such overlap can occur not just within international environmental legal regimes but also between them and other legal regimes. This factor determines the current efforts of global community to establish coordination and coherence between the different regimes with a view of more efficient implementation at the universal, regional and national scales. The climate change regime is not an exception:
Because of the intricate connections between climate change and other issue areas, one may observe a number of interrelationships between the international climate change treaties and other international legal regimes. Some degree of normative interaction and overlap is likely inevitable given the scope of the phenomenon and perhaps even necessary for integrated efforts to limit greenhouse gas emissions and mitigate the detrimental impacts of a changing climate. What is more, such overlap can also breed synergies, both substantive and institutional and may thus have beneficial consequences. However, on a systemic level, normative interaction may give rise to substantive conflicts between different areas of law (Van-Asselt, Francesco & Michael, 2008; Huggins & Karim, 2016; Rei, Goncalves & De-Souza, 2017).
The authors of these lines describe the problem of fragmentation and building synergies in climate change regime and between climate change and other related regimes.
In June 2017, the USA President announced that the United States would withdraw from the Paris Agreement (2015) because it could undermine American economy. Almost the same happened in 1997 when US Senate Byrd-Hagel Resolution declared that the United States should not be a signatory to any agreement on CC which would mandate new commitments to limit or reduce greenhouse gas emissions for Developed Country Parties, unless such agreement also mandated new specific scheduled commitments for Developing Country Parties or resulted in serious harm to the U.S. economy (Byrd-Hagel Resolution, 1997). Since the Paris Agreement has envisaged commitments for developing countries within the framework of the common but differentiated responsibilities' principle (means that in view of the different contributions to global environmental degradation in general and to climate change in particular, States should have common but differentiated responsibilities), the logics of the US current unilateral withdrawal is grounded only on economic considerations. Although this withdrawal will become possible in 2019 and take effect in 2020 due to the Article 28 of the Paris Agreement (Paris Agreement, 2016), it will undermine global efforts in combating climate change making legal regulation more piecemeal and fragmented. Some European Union unilateral actions related to aviation taxes and shipping emissions may also be considered as undermining multilateral negotiations but there is deep difference between American and European unilateralism: the first one doesn't provide for any alternative solutions. Bearing in mind the reference of the CC treaties to the concept of sustainable development which stipulates the integration of economic, social and environmental activities and, thus, makes such an integration a necessary prerequisite for fighting fragmentation in different fields of international interstate cooperation including CC, we may consider the American declaration as contrary to comprehensive and sustainable climate change policy-making.
The issues of international legal fragmentation in general (Alatalo, Jagerbrand & Molau, 2016; Cadman et al., 2016; Simma & Dirk, 2006) or in international environmental law (Cadman, Maguire & Sampford, 2016; Chambers, 2008; Scott, 2011) as well as fragmentation alongside with synergies for climate change policy in particular (Van-Asselt, Francesco & Michael, 2008; Roberts, 2010; Goeteyn, 2013; Parson, 2014; Boyd, 2014; Savaresi, 2017) has been discussed in many academic works. Meanwhile, they lack comprehensive legal analysis of the fragmentation and synergies concerning climate change regime, especially with regard to new developments such as unilateral declaration of the USA President to withdraw from the Paris Agreement, Kigali Amendment to the Montreal Protocol, work of the UN International Law Commission on the protection of the atmosphere or the Energy Community Treaty reforming initiatives. This article provides the study of the fragmented nature of CC regime and building synergies for improving its efficiency through the prism of the sustainable development concept and 'multilateralism versus unilateralism' conflict. That direction has a potential for further scientific research.
The purpose of this article is to analyse the issue of fragmentation and synergy in international law in general as well as in climate change regime in particular, to explore fragmentation and synergies in international legal regime for climate change at the interdisciplinary level, to find out positive and negative perspectives of the phenomenon of fragmentation in the context of CC.
FRAGMENTATION AND SYNERGY IN INTERNATIONAL LAW
The United Nations International Law Commission (ILC) took up the topic of fragmentation of international law in 2000. In 2002, the Commission decided to include the topic, titled 'Fragmentation of International Law: Difficulties Arising from the Diversification and Expansion of International Law' in its current work program and to establish a Study Group (International Law Commission, 2006). In 2006, the Group presented its Conclusions covering the issues of relations between special and general law, prior and subsequent law, relations between laws at different hierarchical levels, etc. The Group determined that the fragmentation of the international social world has attained legal significance especially as it has been accompanied by the emergence of specialized and (relatively) autonomous rules or rule-complexes, legal institutions and spheres of legal practice (International Law Commission, 2006). It must be observed that legal fragmentation is merely 'an ephemeral reflection of a more fundamental, multi-dimensional fragmentation of global society itself' (Dedinec et al., 2016; Liao, 2016; Simma & Dirk, 2006).
The ILC approached the phenomenon of fragmentation from both positive and negative perspectives: on the one hand, fragmentation creates the danger of conflicting and incompatible rules, principles, rule-systems and institutional practices, but, on the other hand, it reflects the rapid expansion of international legal activity into various new fields and the diversification of its objects and techniques (International Law Commission, 2006). One more dimension of fragmentation in international law is the potential conflict between general (universal) and regional legal rules. In the negative sense, regionalism would exempt States within a certain geographical area from the binding force of an otherwise universal rule or principle; a separate, much more difficult case is the one where it is alleged that a regional rule is binding on a State even when the State has not specifically adopted or accepted it (International Law Commission, 2006).
The emergence of so-called self-contained regimes, such as 'trade law', 'environmental law', 'human rights law', 'climate change law', etc. contributed in a certain way to the problem of incoherence of general international law, its instability and inconsistency, which brings about normative and institutional collisions. The principal characteristic of a self-contained regime is its intention to totally exclude the application of the general international law on State responsibility, in particular resort to countermeasures by an injured State (Duyck, 2015; Simma & Dirk, 2006; Yamin & Depledge, 2004). Each 'self-contained
regime' has its own set of principles and rules, which may sometimes conflict with and deviate from general international law. The process of diversification and decentralization has been particularly evident in the environmental context. One can observe fragmentation among international environmental law and other self-contained regimes (e.g. international trade law) and among various regimes within international environmental law (e.g. between...