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Dieses Kapitel untersucht die klimapolitischen Bemühungen der subnationalen Regierungen, die Teil der 2015 gegründeten Under2 Coalition (U2C) sind. Er vergleicht die Leistung der Gründungsmitglieder mit denen, die später beitraten, und beurteilt, ob die Gründungsmitglieder größere klimapolitische Anstrengungen zeigen und ob diese Unterschiede im Laufe der Zeit aufrechterhalten werden. Das Kapitel bietet einen historischen Kontext der internationalen Klimakooperation und hebt die Rolle der subnationalen Regierungen bei der Förderung des Klimaschutzes hervor. Er skizziert auch die Mission und Führungsstruktur der U2C und betont ihr Bekenntnis, die globale Erwärmung auf 1,5 Grad Celsius zu begrenzen und bis 2050 Netto-Null-Treibhausgasemissionen zu erreichen. Die Analyse basiert auf detaillierten Fallstudien aus den Vereinigten Staaten, Kanada, Deutschland, Spanien und Großbritannien und bietet Einblicke in die Führungsdynamik innerhalb der Koalition. Das Kapitel schließt mit einer Synthese der Ergebnisse und der Diskussion der umfassenderen Implikationen für die subnationale Klimapolitik.
KI-Generiert
Diese Zusammenfassung des Fachinhalts wurde mit Hilfe von KI generiert.
Abstract
This introductory chapter formulates the overarching research interest of the book: the examination of climate policy effort among subnational governments in the Under2 Coalition, a transnational network founded in 2015 by regional jurisdictions committed to limiting global warming to 1.5°C. The central research question asks whether Under2 Coalition founding members demonstrate greater and more sustained climate policy effort compared to early joiners (2015–2016) and later joiners (post-2016) within their respective national contexts. Drawing on the conceptual framework of climate leadership and followership, the study conducts systematic comparative analysis across five countries: the United States, Canada, Germany, Spain, and the UK. The analysis focuses on quantifiable indicators including policies, policy instruments, and greenhouse gas emissions reduction targets over the decade since the Under2 Coalition’s establishment. The research contributes to understanding how subnational climate leadership manifests itself in multilevel governance systems and provides a replicable methodological template for examining climate policy dynamics in the members of transnational networks beyond European and North American contexts.
This book focuses on climate policies adopted by subnational governments in multilevel polities that have joined the Under2 Coalition (U2C), founded in 2015. Over the past 20 years, subnational governments have become recognized as key players in addressing climate change (Dubash, 2021), either independently or by joining transnational organizations like U2C.
We seek to understand whether founding members of U2C (i.e., those who signed the founding document) demonstrate greater climate policy effort compared to early joiners (i.e., those who became parties in 2015–2016) and later joiners (i.e., those who became parties after 2016). We define policy effort as the level of activity and ambition in climate action. Additionally, we examine whether such performance differences, if observable, are sustained over the decade since the founding of U2C.
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To motivate our research perspective and position it within the existing literature, we first briefly review developments in international climate cooperation, as this context—along with national-level dynamics—shapes the environment in which subnational governments operate.
The foundation of climate governance was laid in 1988 when the United Nations (UN) recognized climate change as an issue requiring international cooperation and established the Intergovernmental Panel on Climate Change (IPCC) as the authoritative body for providing scientific information on climate change (Hermansen et al., 2023). At its Conference on Environment and Development in 1992, the UN launched a process for negotiating an international agreement to limit dangerous anthropogenic climate change. The resulting international treaty between the participating countries was the UN Framework Convention on Climate Change (UNFCCC), which established the basic legal framework and principles for international climate cooperation. It was signed throughout June 1992 and 1993 and became effective on 21 May 1994, marking the beginning of formal multilateral climate governance (Kuyper et al., 2018).
The next milestone in UN-led international climate cooperation was the negotiation of the Kyoto Protocol, which extended the UNFCCC and committed the signatory states to legally binding targets for reducing greenhouse gas (GHG) emissions. The Protocol represented the first attempt to establish quantified GHG emissions reduction commitments for developed countries. The Kyoto Protocol was signed in 1997 but only entered into force on 16 February 2005, following Russia’s ratification (Henry & Sundstrom, 2007), with the first commitment period starting in 2008 and ending in 2012.
A governance framework for climate change mitigation beyond 2012 should have been negotiated and agreed upon at the 15th session of the Conference of the Parties (COP 15) to the UNFCCC held in 2009. COP 15 was widely anticipated as a critical juncture for global climate governance, with expectations running high for a comprehensive post-Kyoto agreement. However, the parties were unable to reach consensus on a binding agreement, instead producing only the non-binding Copenhagen Accord—named after the host city of COP 15. This outcome drew significant criticism from parties that had advocated for a more ambitious legally binding treaty, as well as from numerous non-state and subnational actors (Dimitrov, 2010).
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The perceived failure of COP 15 is widely regarded as having produced a “Cambrian explosion” of alternative forms of cooperation beyond the UNFCCC; these are based on transnational cooperation rather than traditional international cooperation, making climate governance more complex (Keohane & Victor, 2011) and polycentric (E. Ostrom, 2010, 2011; V. Ostrom et al., 1961; Jordan et al., 2018, 2015; Jordan & Huitema, 2014; Tobin et al., 2024).
By the signing of the Paris Agreement in 2015 at the latest, subnational governments had emerged as a relevant force in advancing climate action (Bäckstrand et al., 2017), demonstrating leadership through policy innovation, early adoption of ambitious GHG emissions reduction targets, and implementation of concrete climate policy measures (Francesco et al., 2020). These initiatives include transnational networks such as the Global Covenant of Mayors (Kona et al., 2021), C40 Cities Climate Leadership Group (Heikkinen et al., 2019), International Council for Local Environmental Initiatives (ICLEI) (Francesco et al., 2020), and U2C (Unger & Thielges, 2021).
While all these initiatives possess interesting features and studying each can provide important insights into climate governance, U2C stands out for several reasons. First, it is composed of governments operating between the national and local levels, thus acting on behalf of larger geographical and jurisdictional units. Second, U2C has concrete, measurable commitments centered on the specific target of limiting global temperature rise to under 1.5 degrees Celsius, which enables systematic assessment of whether members are actually delivering on their stated ambitions. Third, the way U2C was established makes it straightforward to identify founding members and compare their climate policy profiles to those who joined later, which makes it an analytically rewarding case to study.
This chapter provides background information on U2C, its origins, structure, and significance within the broader landscape of transnational climate governance. It further outlines the central research interest of this book—examining whether founding members of U2C have demonstrated superior climate policy effort compared to other member subnational governments within their respective national contexts—and sketches out the analytical framework and structure that will guide the subsequent empirical investigation.
Under2 Coalition
Founding Phase
While U2C emerged during a particularly active period of climate institution-building, it stands out for originating from the innovative initiative of subnational rather than national governments. The coalition was formally founded in May 2015 in the run-up to COP21, building on a collaboration between the US State of California and the German State of Baden-Württemberg, two subnational jurisdictions committed to ambitious climate action (Galarraga et al., 2017). Both states already had in place a climate protection law and several policies to cut GHG emissions in specific sectors, including energy generation, energy use in buildings, and transportation (Allison et al., 2016; Jacob & Kannen, 2015). Pre-existing cooperation between the two states, such as through the Transatlantic Climate Bridge initiative launched in 2008, led government officials to recognize the value in creating a formal coalition of subnational actors to stimulate concerted subnational climate action (Thielges, 2019). The formal foundation of U2C rests upon a Memorandum of Understanding (MoU), which serves as the primary governing document while remaining non-legally binding in nature.1
Another ten subnational governments joined the initiative and, together with California and Baden-Württemberg, co-founded U2C in May 2015. Founding U2C reinforced pre-exisiting partnerships among these governments. The Brazilian state of Acre was already a subnational leader in curbing deforestation and forest degradation at that time (Climate Focus, 2013). Prior to co-founding U2C, Acre had partnered with California as part of the Reducing Emissions from Deforestation and Forest Degradation Offset Working Group (Gueiros et al., 2023).
Baja California and Jalisco were the two Mexican states that co-founded U2C. Jalisco has long been one of Mexico’s most deforested states (García-Jiménez & Vargas-Rodriguez, 2021; Cullenward, 2017). Unlike Acre in Brazil, it was not a leader in counteracting deforestation at the time of U2C’s inception, but began taking policy action afterwards. However, like Acre, it had already been collaborating with California within the framework of the Governors’ Climate & Forests Task Force (GCF).
Baja California in Mexico and the US state of California share a border and had already established close ties before co-founding U2C. They had collaborated on renewable energy projects (particularly wind power) and other climate initiatives as part of an agreement between California and the Mexican Ministry of Environment and Natural Resources, which can be seen as a direct precursor to Baja California’s involvement in U2C.
British Columbia and Ontario were the two Canadian co-founding members (see also Chap. 4). They had pre-existing ties with California through their membership in the Pacific Coast Collaborative (PCC), a regional cooperation on energy and environmental matters, and the Western Climate Initiative (WCI), a regional collaboration launched in 2007 by US states and Canadian provinces to design a multi-jurisdictional cap-and-trade program (Cullenward, 2017; Houle et al., 2015).
Oregon, Vermont, and Washington were the other three co-founding states from the United States (see also Chap. 3). Oregon was one of the early movers in US climate action and had already forged climate partnerships with California, most notably as a co-founding member of both the PCC and the WCI. Similarly, Vermont had been a member of the Regional Greenhouse Gas Initiative (RGGI), implementing a cap-and-trade system for the power sector together with other northeastern US states (Yan, 2021). As a signatory to the WCI, it also had prior exchanges with California on climate policy. Finally, Washington had already-established ambitious statutory GHG emissions reduction targets by 2008 and co-founded both the PCC and the WCI in collaboration with California and Oregon (Cullenward, 2017).
The Spanish autonomous region of Catalonia and Wales were the European co-founding members. Both were climate leaders well before U2C’s inception (see also Chaps. 6 and 7). They had also collaborated with Baden-Württemberg and California through pre-existing partnerships, including the Network of Regional Governments for Sustainable Development (NRG4SD) and the Climate Group’s States & Regions Alliance (CGSRA). Founded in 2005, the latter served as a key pre-Under2 forum that enabled Catalonia to collaborate with the other European members on subnational commitments, climate target benchmarking, and joint advocacy at COPs (Happaerts et al., 2010).
Expansion over Time
Numerous subnational governments joined U2C at a series of events throughout 2015, including the World Summit on Climate and Territories in the Rhône-Alpes Region of France, the Climate Week in New York City, and the World Expo hosted by Milan, Italy. Figure 1.1 visualizes the global distribution of U2C signatories by the end of 2015.
Fig. 1.1
Countries with Under2 coalition signatories in 2015. Note: Colors denote a country’s percentage share of subnational entities that have joined U2C
In North America, the Canadian province of Québec joined, having been part of the WCI and having already formally linked its cap-and-trade system with California in 2014 (Houle et al., 2015). In the United States, Connecticut, Massachusetts, Minnesota, New Hampshire, New York State, and Rhode Island joined the four founding US states. All of these new members, except for Minnesota, were already part of the regional RGGI of the northeastern US states.
In Latin America, the Brazilian states of São Paulo and Mato Grosso joined, along with Mexico State from Mexico. The Ucayali region was the first to join from Peru. Located in the Peruvian Amazon, it shares a border with the U2C co-founding state of Acre in Brazil. Ucayali had also been a member of GCF and was therefore already connected with California as well as with the Brazilian and Mexican co-founding states of U2C.
In Europe, Baden-Württemberg was joined by the German states of Bavaria, Hesse, North Rhine-Westphalia, Schleswig-Holstein, and Thuringia. Similarly, the Basque Country and the Foral Community of Navarre joined Catalonia in Spain. Additional regions joined from France (Aquitaine, Brittany, Occitanie, Poitou-Charentes, and Rhône-Alpes), Italy (Emilia-Romagna, Lombardy, Piedmont, and Sardinia), the Netherlands (Drenthe), Portugal (Azores andMadeira), and Sweden (Jämtland and Härjedalen).
A smaller number of subnational actors joined U2C from Asia and Oceania. South Australia was the first Australian state to participate. The Chinese provinces of Jiangsu and Sichuan signed the U2C MoU, building on an evolution of climate partnerships between California and Chinese provinces dating back to the 1970s (Jin, 2025). The Japanese prefecture of Gifu also joined, having previously been a member of ICLEI. Finally, the Kathmandu Valley in Nepal signed the U2C MoU in 2015 as well.
The coalition has grown steadily since 2015. A larger number of new signatories joined U2C in 2021 in the run-up to COP26 in Glasgow and in 2022 in the run-up to COP27 in Sharm el-Sheikh. Remarkably, all regions of Morocco became members of the network at the conference.
By 2024, around 10% of subnational entities had signed the U2C MoU, making it a global network spanning all five major continental regions. Figure 1.2 shows the distribution of the more than 183 signatories across the globe in 2024.
Fig. 1.2
Countries with U2C signatories in 2024. Note: Colors denote a country’s percentage share of subnational entities that have joined U2C
Some founding members of U2C were especially successful in attracting new signatories within their own countries. Brazil stands out, with nearly 75% of Brazilian states following Acre to join the network. Many of these joined during Jair Bolsonaro’s presidency between 2019 and 2023, when climate protection was weakened at the federal level and subnational climate action became even more urgent (Milani et al., 2025). The Climate Pathway Project (CPP) was initiated during this period, empowering the subnational governments of Amazonas, Mato Grosso, and São Paulo to develop policy pathways for long-term emissions reductions under U2C guidance. Similarly, 19 Mexican states—approximately two-thirds of all Mexican states—are now U2C members. Three of these (Quintana Roo, Querétaro, and Madre de Dios) have also participated in the CPP, developing policy pathways for long-term GHG emissions reduction.
In the United States, 17 states signed the Under2 MOU, representing 33% of all US states. All are “blue” states with historically Democratic dominance, reflecting the bipartisan polarization of climate action in the United States. In Canada, only the Northwest Territories joined after 2015, meaning four Canadian subnational entities (33%) are U2C members today. In Europe, 80% of UK subnational governments participate in the coalition, as Northern Ireland and the Isle of Man joined in 2021. In Germany, seven additional states joined Baden-Württemberg, totaling 50% of the country’s states. Finally, Spanish signatories increased to six, representing 31% of Spanish subnational entities.
Some non-founding countries also witnessed a significant rise in new signatories to the Under2 MOU. Australia has a strong legacy of subnational climate action, contrasting with a long period of national-level inaction (Christoff & Eckersley, 2021); indeed, three-quarters of Australian states are U2C members today. France is another non-founding country that saw numerous regions join the coalition, with more than half of its 13 regions having signed the MoU (54% of subnational governments).
Mission and Governance Structure
The signatories of the MoU commit themselves to limiting global warming to no more than 1.5 degrees Celsius above preindustrial average temperatures. Additionally, U2C members have pledged to achieve net-zero greenhouse gas emissions by 2050, with many jurisdictions striving to achieve this even earlier.2
Alongside comprehensive mitigation action, U2C members also actively collaborate on adaptation and resilience measures to address the impacts of climate change. According to the foundational MoU, U2C parties commit to collaboration and coordination efforts designed to advance their respective interim targets for GHG emissions reductions, ensuring these remain consistent with their overarching 2050 goals and broader climate action strategies. Collaboration takes place through multiple structured venues, including the annual U2C General Assembly, which serves as the primary governance forum, the annual sessions of the COPs, and various other significant international climate events and summits.
The collaborative framework encompasses several key operational areas. The parties actively share and promote effective financing mechanisms and innovative funding approaches to support climate action implementation. They also facilitate comprehensive technology sharing and knowledge transfer initiatives. Members work together to build institutional capacity for both climate action and technology adaptation through systematic technology transfer programs and the exchange of technical expertise and best practices. Additionally, they engage constructively in specialized programs and projects developed by other member parties and/or coordinated by The Climate Group as the secretariat organization.
Furthermore, to ensure continued effectiveness, the parties have agreed to conduct comprehensive reviews of the ongoing relevance and functionality of the MoU every five years, strategically aligning this review cycle with the Paris Agreement’s established five-year cycle of increasingly ambitious climate action and enhanced commitments to reducing GHG emissions.
Conceptual and Research Framework
Our analytical framework draws on the seminal work of Liefferink and Wurzel (2017), particularly their nuanced conceptualization of “leadership” and “followership” dynamics in climate governance (see Chap. 2 for details). Liefferink and Wurzel’s framework distinguishes between different types of actors based on their temporal entry into climate initiatives and their subsequent behavior patterns. Climate leaders are characterized not merely by early adoption of climate policies, but by their willingness to undertake ambitious climate action that exceeds minimum requirements and serves as a model for others. These actors typically demonstrate higher levels of commitment in their climate strategies. Conversely, followers enter governance arrangements after initial frameworks have been established, often adopting more cautious approaches that align with proven models rather than pioneering new pathways.
This leadership-followership dynamic becomes particularly relevant in the context of subnational climate governance, where regional and local authorities operate within complex multilevel systems that include national governments, international organizations, and transnational networks. U2C represents an instructive case study for examining these dynamics, as it emerged from subnational initiative rather than top-down national or international mandate, creating distinct opportunities for genuine leadership expression at the subnational level.
Building on this foundation, Chap. 2 argues that U2C’s founding members demonstrate higher and more sustained levels of climate policy effort than entities that joined later. We interpret higher climate policy effort as indicating climate leadership, while lower policy effort suggests climate followership.
Assessing subnational climate policy effort presents several methodological challenges that our research framework addresses. First, climate policy effort is context-dependent, varying according to jurisdictional capacities, economic structures, political systems, and baseline conditions. A jurisdiction with abundant renewable energy resources may demonstrate leadership through rapid clean energy deployment, while another with limited natural advantages might show leadership through innovative policy design or ambitious targets despite challenging circumstances.
To address these differences systematically, we conduct detailed comparative analysis between U2C founding members, early joiners, and subsequent joiners, with particular attention to subnational entities from the same national contexts. This approach allows us to control for national-level variables such as the policy competences granted to subnational governments, federal climate policy frameworks, economic conditions, and public attitudes toward climate action.
Furthermore, our analysis focuses on quantifiable indicators of climate leadership, including policies, policy instruments, and GHG emissions reduction targets (Schaub et al., 2022; Steinebach et al., 2024). Additionally, our analysis considers the temporal dimension of climate action, examining whether founding members maintain their leadership positions or whether subsequent joiners eventually converge toward similar levels of ambition.
Second, the temporal dimension of climate policy effort presents challenges in attribution and assessment. Climate policies often have long implementation timelines and may not show immediate results in terms of emissions reductions or other quantitative outcomes (Boasson et al., 2025). The research framework therefore examines both short-term policy outputs and longer-term commitments in the form of GHG emissions reduction targets.
Third, the multilevel nature of climate governance means that subnational climate action occurs within complex institutional environments involving multiple levels of government and diverse stakeholder groups. The framework accounts for these interactions while focusing specifically on the role of subnational governments in policymaking within these broader governance arrangements.
Organization of the Book
This book progresses logically from theoretical foundations through detailed empirical case studies to synthesized findings and concluding remarks. Chapter 2 presents the framework that serves as the theoretical backbone guiding all subsequent empirical analysis throughout the book. The book’s empirical core consists of five detailed case study chapters that systematically compare climate policy effort among founding members, early joiners, and later joiners (within specific national contexts).
Chapter 3 provides the most extensive analysis of the entire book, examining the United States, where 4 founding states—California, Oregon, Vermont, and Washington—are systematically compared with 13 states that joined the U2C in later periods. This chapter leverages the rich US context, which hosts the largest absolute number of U2C members, to provide the most comprehensive empirical insights available.
Chapter 4, the Canadian analysis, systematically compares founding members British Columbia and Ontario with later joiners Québec and the Northwest Territories. The German case is studied in Chap. 5 and contrasts Baden-Württemberg’s distinctive pioneering role as a co-founding jurisdiction with the climate policy effort of seven states that subsequently joined the Coalition. Chapter 6 evaluates the performance of Catalonia, the Spanish U2C founding member, in comparison to the early joiners—the Basque Country and the Foral Community of Navarre—and the later joiners, including Andalusia, the Community of Madrid, and Galicia. Finally, Chap. 7 compares Wales’ climate policy effort with that of Scotland, an early joiner, as well as analyzes the climate policy effort of later joiners Northern Ireland and the Isle of Man.
Chapter 8 synthesizes the findings through systematic cross-case analysis and comparative evaluation, while Chap. 9 concludes by situating our empirical findings within the broader existing climate governance literature and carefully outlining the most promising research directions for future scholarship focused on subnational climate leadership and transnational climate initiatives.
Contributions to the Literature
The first contribution this study makes to the existing academic literature is its systematic demonstration of how climate policy effort and leadership dynamics have developed and evolved over time within the U2C framework. We examine how climate leadership manifests itself concretely in terms of the specific policies adopted, the diverse policy instruments employed, and the level of ambition of the GHG emissions reduction targets set by the members. Our analysis provides insights into how U2C founding members, early joiners, and later joiners exercise different forms of climate leadership and—with less theoretical emphasis—followership, revealing distinct patterns of engagement and commitment levels across temporal membership categories.
The second contribution lies in our provision of both a research framework and empirical insights that are genuinely comparative across two analytic dimensions. First, our study offers a systematic comparison of founding members, early joiners, and later joiners across five countries. This careful case selection deliberately incorporates variation within these countries—examining different subnational entities within the same national context—as well as meaningful variation across these nations and even between continents, since our research scope encompasses U2C members distributed across both Europe and North America.
The constitutional distribution of climate policy competence varies significantly across these five countries. Germany’s concurrent legislation principle creates a constrained environment where states must navigate narrow windows for policy action (Eckersley et al., 2023). The United States presents the opposite extreme, with its highly decentralized federal structure granting states broad policy powers (Mildenberger, 2021). Spain’s quasi-federal system illustrates the tensions inherent in unclear constitutional boundaries, and like Germany, it is affected by European Union (EU) policies. In Canada, substantial jurisdictional overlaps between national and provincial governments create both opportunities and obstacles (Henstra, 2017). The UK’s constitutional asymmetry creates distinct challenges and opportunities across its constituent nations (Royles & McEwen, 2015).
Along similar lines, our analysis over extended time periods provides empirical evidence on the temporal dimension of climate policy effort and leadership. We assess how robust these leadership patterns remain when confronted with significant changes in the higher echelons of political systems, including shifts in national governments, policy priorities, and other economic, political, and social developments, including socio-political backlash to climate action (Patterson, 2023).
Our third distinctive contribution to the scholarly literature is that we offer a replicable methodological template for expanding this research approach to examine climate action by U2C parties beyond the European and North American contexts. We identify ideal candidates for extending this comparative research framework, highlighting Brazil and Mexico as priority countries since they host three additional founding members of U2C: the Mexican states of Baja California and Jalisco, and the Brazilian state of Acre. These jurisdictions represent potentially insightful cases for understanding how subnational climate leadership emerges in different political, economic, and institutional contexts within Latin America and how leadership shapes climate policy effort.
While this research maintains a deliberately well-defined empirical focus that enables depth of analysis, we acknowledge that there are numerous important aspects of climate leadership by subnational entities and the broader institutional functioning of U2C which we cannot comprehensively cover within the scope of this study. These limitations include detailed analysis of implementation mechanisms, extensive examination of policy outcomes, and comprehensive assessment of the effectiveness of U2C governance structures.
Despite our necessarily focused analytic approach, we remain confident that our findings will significantly reduce existing gaps in the scholarly understanding of subnational climate governance dynamics and provide valuable insights for both academic researchers and policy practitioners working in this rapidly evolving field. By bridging theory and practice in this way, this study contributes to the broader effort to understand how multilevel climate governance can be strengthened and sustained over time.
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The UNFCCC states its explicit intention to “pursue efforts to limit the [global] temperature increase to 1.5°C above pre-industrial levels” and the IPCC was invited to “provide a special report in 2018 on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways” (Hulme, 2016, p. 222). The original MoU of U2C was revised in 2021 to align it with the 1.5 degrees Celsius target of the Paris Agreement.
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