How do global and regional climate targets, rules, policies, and standards emerge and under which conditions are they effectively enabled within domestic political systems? When and how do national policy innovations diffuse and who are the principle actors involved? This paper aims to shed light on the multilevel intermediation processes that shape climate policy development and implementation, with a particular focus the interplay between the United Nations Framework Convention on Climate Change (UNFCCC), regional multilateral institutions, and their member states. As per the original project deliverable, the aim of this study is both descriptive – providing a detailed and historical perspective on “multi-level implementation of the UNFCCC regime through coordinated action within and between member states” – as well as analytical, namely, to assess its “effectiveness and ability to accelerate climate governance implementation”. It builds upon earlier ground-clearing research that produced a comprehensive mapping of the current UNFCCC regime and the wider climate governance regime complex, illuminating scope for action by a wide variety of actors at all scales, from the sub-national to the highest global level of political assembly (Coen, Kreienkamp, and Pegram 2020). By focusing on interscalar interactions on the regional level, this paper zeroes in on particularly important dynamics within this complex ecosystem of global climate governance. More specifically, we compare governance arrangements in the European Union (EU), where supranational climate policymaking is most advanced, to those in the Association of Southeast Asian Nations (ASEAN), where regional cooperation on climate change remains very limited.1 Regional organizations provide an instructive domain of analysis because they sit neither at the “top” nor at the “bottom” of the global climate change regime, providing vital governance (regulatory) as well as meta-governance (steering) functions.2 Although there are significant differences between the EU and ASEAN, both case studies point to linkages between global, regional, and national climate governance, with the international framework setting boundary conditions for regional and national policy development and vice versa. However, while these linkages have, at several points in time, accelerated policymaking processes in the EU, they have created few opportunities for significant policy change within ASEAN. Whereas our previous mapping of the global climate governance landscape employed scholarship on regime complexity to illustrate the growing institutional diversity on the inter- 1 This emulates recent scholarship seeking to advance comparative leverage between the EU and ASEAN focused on institutional design, in light of temporal and spatial variation in regional integration processes (Hofmann and Yeo 2017). 2 Meta-governance arrangements do not regulate or govern directly but rather engage in the “organization of self-organization” by providing ground rules for and ensuring the coherence and consistency of different governance regimes and mechanisms, whether through networks, markets, or hierarchical steering (Jessop 1998, p. 42). 4 and transnational level, this paper aims to provide a more sophisticated account of the governance dynamics playing out within this cluster of institutional arrangements through a multilevel governance (MLG) lens. Given space constraints, our focus is on the UNFCCC regime, which remains at the core of the broader climate regime complex (Keohane and Victor 2011). While the regime complexity literature is primarily concerned with the rising density of institutions on the same level of governance and the resulting proliferation of overlapping rules (Alter and Meunier 2009), MLG is more concerned with linkages and interactions between multiple scales and levels of governance and how this affects where policymaking authority is located. This provides a useful frame for exploring if, how, when, and why the UNFCCC regime affects the design of regional and national institutional arrangements and how, in turn, actors at various levels of governance seek to shape the rules and institutions that make up the regime. We show how MLG structures can be exploited by progressive policy entrepreneurs, who advance novel policy solutions, as well as policy obstructers who, for various reasons, are invested in the status-quo. To do so, we employ John Kingdon’s (1984) multiple streams framework (MSF), which highlights both the structural conditions that facilitate or impede non-incremental policy change – problem perception, availability of policy solutions, and political willingness – as well as the ability of different agents to exploit these conditions. Understanding these processes, and under which conditions they result in more ambitious climate action, is vital for any efforts to make existing governance arrangements more effective. As such, this paper speaks not just to scholars of global governance, International Relations, public policy, and related disciplines but first and foremost to policymakers at various levels of decision-making, seeking to better understand and reform policy processes. We supplement the EU and ASEAN case studies – which focus primarily on vertical interactions in multilevel governance arrangements – with a case study on transnational policy diffusion, tracing how national climate framework laws have emerged as important governance tools for internalizing UNFCCC rules and norms, mostly in Europe but increasingly beyond. Climate laws are significant because they enshrine binding long-term mitigation targets and establish overarching governance frameworks to realize these targets. While they have primarily diffused horizontally, we also document how policy entrepreneurs have recently managed to “upload” the concept to the EU-level. Some design elements of climate framework laws are even reflected in the Paris Agreement. Because the latter does not set legally binding mitigation targets for individual countries, relying instead on voluntary national commitments, climate laws can provide an important “link between international obligations and national policymaking” (Nash and Steurer 2019, p. 1061). However, for mitigation commitments to be meaningful, accountability structures must be in place to ensure that targets are grounded in science and implemented effectively. As we will show, independent climate advisory bodies 5 (ICABs) can play an important role in this regard – but only if they are properly resourced and vested with requisite powers. To date, only a handful of countries, primarily in Europe, have implemented strong and robust climate laws, with ambitious and quantifiable long-term targets, clear governance provisions, and ICABs that are not just offering scientific advice but also rigid progress monitoring. Meanwhile, in the ASEAN region, long-standing structural limitations to political accountability, participation, and civil society engagement have impeded the development of climate laws and formal ICABs. However, as we will argue, the emergence of informal monitoring regimes comprised of domestic civil society organizations could provide an alternative, albeit “softer”, avenue for driving more ambitious climate action and holding governments to account. This paper begins by introducing multilevel governance (MLG) and the multiple streams framework (MSF), which provide the theoretical anchor for our case studies. We then apply these concepts to reflect on the development of climate governance in the EU, with particular focus on the interplay between the EU and the UNFCCC. This is followed by a case study on ASEAN, where regional climate governance structures are much less developed and there is little coordinated engagement with the UNFCCC regime. To illustrate the diversity of national approaches within ASEAN and identify obstacles and opportunities for more sophisticated climate governance arrangements, we supplement the regional case study with reflections on the current situation in Indonesia and Singapore. The next part of the paper focuses on national climate framework laws, explaining their emergence and ongoing diffusion as well as weighing in on their potential as innovative governance solutions. The paper concludes by reflecting on the future of global, regional, and national climate governance in light of conflicting problem definitions and the need for urgent action, even in the face of other pressing challenges, such as the coronavirus (COVID-19) pandemic.