9. Conclusion
- Open Access
- 2026
- OriginalPaper
- Buchkapitel
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Abstract
Introduction
The proliferation of transnational networks connecting subnational governments represents a noteworthy development in contemporary climate governance (Bäckstrand et al., 2017; Francesco et al., 2020; Heikkinen et al., 2019; Tosun et al., 2023; Unger & Thielges, 2021). These networks enable knowledge sharing, peer learning, and collective action among jurisdictions that might otherwise operate in isolation (Boyd, 2017).
This book investigated the U2C and sought out to examine whether founding members of U2C demonstrate greater climate leadership and policy effort compared to subnational governments that joined the coalition later. Through detailed case studies we assessed climate policy effort across multiple dimensions and over time. Our research design specifically addressed the temporal dimension of climate policy effort, recognizing that leadership manifests itself not only in early policy adoption but also in maintaining ambitious policies despite changing economic, social, and political contexts. In this concluding chapter, we are now positioned to provide answers to our central research questions.
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Main Findings
Assessment of the Propositions
Our first proposition formulated in Chap. 2 argued that reputational incentives are linked to levels of climate policy effort, influencing both the scope of activity and level of ambition. We further argued that U2C founding members should be particularly susceptible to reputational costs if they lower their climate policy effort. This effect should be present for early joiners but less so for later joiners. The second proposition rests on the same argument but applies it to the temporal stability of climate policy effort over time: reputational incentives should help to maintain the level of climate policy effort by founding members and—though possibly to a lesser extent—by governments that joined U2C later.
For the United States, California’s policy development fully aligns with both propositions, though the empirical picture is more mixed for the other U2C founding members and for early joiners in the United States. Even so, the US data showed that later joiners demonstrate less policy effort than founding members and early joiners.
The findings for Canada revealed that U2C founding members maintained and enhanced their subnational climate policy effort—with the exception of Ontario. This reversal, despite the reputational costs of abandoning a flagship U2C initiative, illustrates how domestic political dynamics can overwhelm international commitments.
In Germany, Baden-Württemberg, as a founding member, has also been more eager to show sustained climate policy effort than the other states, whereas Bavaria and Thuringia have exhibited less climate policy effort despite being early joiners.
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Broader support for the proposition was observed for the subnational governments in Spain, with Catalonia demonstrating particularly high climate policy ambition. This observation is even more remarkable considering that Catalonia’s Law 16/2017 on Climate Change was partially struck down by the Constitutional Court in 2019 due to ambiguities in the constitutional rights of the autonomous communities in Spain. This forced the Catalonian government to pursue climate objectives through decree laws and alternative mechanisms.
The UK emerged as a noteworthy case since Scotland, an early joiner, consistently demonstrated higher climate policy effort than Wales, a founding member. An important element in explaining this is the UK’s constitutional asymmetry, which creates distinct challenges and opportunities across its constituent nations. Scotland’s greater autonomy, secured through successive devolution settlements, enables climate policy exceeding UK ambitions, whereas Wales remains deeply entangled with English policy (Royles & McEwen, 2015).
The chapters on Canada, Spain, and the UK explicitly examined whether the climate policy effort made by the subnational entities could be attributed to their U2C membership. While we cannot establish a causal connection, it is worth noting that Northern Ireland and the Isle of Man, two later joiners, increased their climate policy effort following their entry into the coalition, indicating that U2C participation may serve as one contributing factor among many in driving enhanced climate action at the subnational level. On the other hand, the U2C membership of Andalusia happened at a point in time when it already had a high level of climate policy effort, suggesting that membership is not the driving force behind its climate policy effort.
Overall, the empirical insights support the proposition that U2C membership influences climate policy effort over time, but they also revealed that we must pay attention to several additional factors. One of these factors—as already discussed above—refers to the constitutional setup in the countries where subnational governments operate, which defines the formal opportunity structure for their climate policy efforts.
The analyses of subnational governments in Canada, Germany, and the United States elucidated the importance of the regional government’s ideological composition. In Canada, Ontario’s cap-and-trade program was repealed following a change in partisan control, where the Progressive Conservative Party replaced the Liberal Party in government. In Germany, states with Green Party participation in government consistently demonstrate higher climate policy effort. Baden-Württemberg’s sustained leadership under Green Party Prime Minister Winfried Kretschmann exemplifies this pattern and contrasts sharply with Bavaria’s persistent lagging despite having favorable structural conditions for climate action. Notably, Bavaria’s weaker performance coincides with the fact that the Green Party has never participated in its state government, reinforcing the importance of ideological composition in driving ambitious climate policies.
However, partisan composition is not the only way how political parties and their ideologies matter. The case of Oregon demonstrates that constitutional requirements for policymaking can also constrain political parties’ power. Ambitious climate policy bills failed despite Democrats holding majorities in both the Oregon State Senate and House of Representatives, as Republicans exploited a two-thirds quorum requirement to block legislation.
Furthermore, several chapters illustrated the importance of economic context for climate policy effort and how it has evolved over time. North Rhine-Westphalia’s heavy reliance on coal, despite its early U2C leadership, limited its policy options and constrained stakeholder support for ambitious climate action. Conversely, the analysis showed that jurisdictions with “cleaner” economic structures faced fewer barriers to policy implementation. For instance, service-dominated economies like Madrid and renewable-disposed regions like Québec encountered less economic resistance to higher climate policy effort. This structural variation suggests that effective climate governance requires differentiated approaches that account for local economic contexts rather than ones which pursue uniform ambition levels across jurisdictions.
The assessment of Spain broadened the analytic perspective by highlighting the critical importance of policy implementation, revealing that some subnational governments exhibit high effort in policy formulation but fall short in execution due to insufficient institutional capacity. More precisely, the Foral Community of Navarre’s small administrative apparatus illustrates how size limitations can constrain implementation regardless of political will. The chapter on Spain was not the only one to address constraints in institutional capacity. For instance, the Isle of Man depends heavily on external consultants, while the Northwest Territories in Canada lack technical expertise. Northern Ireland’s unique post-conflict governance arrangements, which include power-sharing requirements and periodic assembly suspensions, create additional implementation challenges that are absent in other UK nations.
Types of Climate Leadership
The chapters offered valuable insights into different types of climate leadership as defined by Wurzel et al. (2019). Structural leadership emerges most clearly in jurisdictions combining constitutional authority, economic resources, and natural advantages. California’s unique CAA waiver exemplifies how constitutional arrangements can enable subnational leadership—no other state possesses this authority to set vehicle emission standards, yet all states can choose to adopt California’s. These elements form the bedrock of California’s structural leadership.
Cognitive leadership through reframing climate action proves particularly powerful in overcoming structural disadvantages. For example, both the Basque Country and Galicia successfully reframed climate policy as economic modernization essential for regional competitiveness and the creation of jobs. This cognitive reframing aligned climate action with regional development priorities, generating broader political support for it.
Entrepreneurial leadership depends on effective coalition building and strategic positioning, which the governments of Québec and California demonstrated when establishing the joint cap-and-trade system in 2014. This innovative arrangement enables the mutual recognition and trading of emissions allowances between the two jurisdictions to address GHG emissions. Galicia exemplifies entrepreneurial use of late membership, deliberately timing its November 2021 accession to coincide with COP26 for maximum visibility. This strategic approach facilitated rapid and comprehensive domestic reform of its GHG emissions reduction targets. The conjunction of international attention and domestic momentum created climate policy windows that earlier membership might not have provided.
Exemplary leadership through policy innovation creates templates for replication across jurisdictions. Connecticut’s green bank model, established in 2011, has been replicated across numerous US states and U2C members,1 as has Hawaii’s 100% renewable electricity target, which was initially dismissed as unrealistic. Another example is Scotland’s Climate Justice Fund, which provided a model for integrating equity concerns into climate finance.
Followership
The empirical analysis revealed that followership is a relevant phenomenon even for U2C members. In this context, our analysis has provided two important insights. First, some subnational governments join U2C to be better able to follow the policy effort of climate leaders. Our analyses did not identify these entities as having the ambition to become leaders within their respective country or the U2C context. Northern Ireland’s 2021 accession followed a decades-long dearth of subnational climate policy, which we can attribute to post-conflict priorities and institutional instability. Its subsequent Climate Change Act (2022) closely emulates Scottish and Welsh approaches, suggesting membership facilitated policy transfer. However, the Climate Change Act does not exceed the level of policy effort demonstrated by Scotland and Wales. The Northwest Territories in Canada similarly used 2017 membership to import southern Canadian approaches while adapting them to Arctic contexts.
Second, some subnational governments strategically positioned themselves as followers initially in order to emerge later as leaders, with Vermont in the United States serving as a compelling example. Initially, Vermont’s government deliberately followed California’s established leadership by adopting and adapting its proven climate policies. This strategic mimicry allowed Vermont to build institutional capacity and policy expertise while avoiding the costs and risks associated with pioneering untested approaches. Eventually, this foundation put Vermont in a strong position to act as a climate leader in its own right, particularly within the context of another transnational collaborative framework: the NEG-ECP. This trajectory suggests that strategic followership can serve as a calculated pathway to leadership, where subnational actors leverage the experiences of pioneers to develop their own capacity for innovation and regional influence.
Our observations regarding the relevance of followership suggest that engaging more profoundly with this group of subnational governments would allow us to acquire a better understanding of climate leadership, which aligns with the main conclusion in the pertinent literature (Tobin et al., 2023; Torney, 2019; Underdal, 1998; Wurzel et al., 2019).
Limitations
We acknowledge that this study, while providing valuable insights into subnational climate leadership dynamics within U2C, operated within certain analytic constraints that have inevitably shaped our findings and conclusions. For one, the analysis’ conceptual engagement with leadership was limited. As explained in Chap. 2, we simply assumed that subnational governments strive to act as leaders, but did not actually test this. Furthermore, we assessed the different types of leadership according to the relevant literature; however, leadership as a concept requires more comprehensive engagement and critical reflection. Even more importantly, although we engaged with followership in the country chapters, we did not theorize its complex relationship with leadership. Consequently, more theorizing is needed to better understand the dynamic relationship between leaders and followers, as well as which factors shape the transition from leader to follower and vice versa (see Torney, 2019).
Moreover, we acknowledge that our analysis does not cover the full range of U2C members and their diverse contexts. Most importantly in this regard, this book focuses exclusively on high-income democracies; we therefore cannot draw meaningful conclusions for subnational units operating in less affluent countries and/or countries that are anocracies or even autocracies, which are substantively represented within the U2C membership. For instance, several subnational entities in Latin American countries partake in U2C and other transnational climate governance initiatives (Tosun et al., 2023). This geographic and political-economic limitation significantly constrains the generalizability of our findings and highlights the need for expanded comparative research that encompasses the full spectrum of U2C participants across different developmental and governance contexts.
However, rather than viewing these limitations as shortcomings, we recognize them as productive starting points for future research endeavors that could substantially enhance our understanding of subnational climate policy across three interconnected dimensions: conceptual, theoretical, and empirical.
Future Research Directions
Our conceptual framework, while grounded in established scholarship on climate leadership and followership, reveals several areas where future research could refine and expand our understanding of leadership and followership in the context of subnational climate governance. First, our conceptualization of climate leadership focused primarily on policy outputs, target-setting, and temporal sequences of action, but future studies could develop more nuanced conceptualizations that incorporate qualitative dimensions of leadership, such as policy innovation as well as the strategies leaders adopt for advocacy and to influence other jurisdictions. Additionally, our distinction between founding members, early joiners, and later joiners represents a necessary simplification for a comparative analysis that accounts for timing, but future research could explore more sophisticated categorizations that take into account the motives determining the decision over whether and when to join climate governance coalitions.
The concept of followership also deserves greater conceptual attention, as our analysis suggests that later joiners may exhibit different forms of climate commitment that do not necessarily represent inferior performance but rather alternative pathways to climate policy effort. In this regard, it was interesting to observe that some of the later joiners initially followed leaders with the ultimate aim of becoming leaders themselves—a dynamic for which we did not account in our conceptual framework.
From a theoretical perspective, our reliance on leadership, while productive, represents only one lens through which to understand the climate policy effort made by subnational governments within transnational networks. Future theoretical development could integrate auxiliary mechanisms to better explain how transnational networks like U2C shape members’ behavior at a particular point in time as well as over time. The empirical chapters have shown that economic, social, and political factors need to be considered alongside the constitutional foundation of countries and how much leeway they leave subnational governments to embrace climate policy and exceed what is defined at the central level.
The multilevel governance literature offers another promising theoretical avenue for expanding our framework. Our analysis controlled for national-level variables but did not systematically theorize the complex interactions between local, regional, national, and transnational governance levels. However, all our case studies have suggested that this interaction is important for explaining the dynamics of climate policy effort at the subnational level. Future research could develop more sophisticated theoretical models that specify how these interactions shape subnational climate policy effort.
Network theory presents additional opportunities for theoretical advancement. While we examined U2C members’ performance, we did not systematically analyze network effects, peer influence, or the role of network position in shaping climate action. Future theoretical development could incorporate social network analysis to understand how relationships within and across transnational climate networks affect policy adoption, implementation, and effectiveness.
Our empirical analysis, while comprehensive within its defined scope, suggests several directions for future research that could significantly enhance our understanding of subnational climate policy effort. First, geographic expansion beyond our European and North American focus represents a crucial next step. As noted, jurisdictions like the Mexican states of Baja California and Jalisco, and the Brazilian state of Acre, offer important opportunities for examining climate leadership dynamics in Latin American contexts, where different political, economic, and institutional conditions may produce distinct patterns of subnational climate action (see, e.g., Tosun et al., 2023).
Geographical extension within the countries from which subnational units participate would also provide valuable empirical opportunities. We are aware that our case selection hinged on the dependent variable, that is, we only assessed subnational entities that participate in U2C. While this perspective has enhanced our understanding of the climate policy effort made by U2C-affiliated subnational governments, we cannot draw any conclusions for those that did not join the coalition. We consider it plausible that U2C members worldwide demonstrate higher levels of climate policy effort; however, our analysis lacks the scope to prove this.
Conclusion
Overall, our analysis revealed that U2C membership is often associated either with existing, high levels of climate policy effort or with increased effort after joining. However, in some instances, subnational governments also reduced their efforts after joining. This latter finding suggests that reputational incentives arising from U2C membership play a role, but they cannot overcome deliberate political action to scale back climate policy or economic or structural constraints (Patterson, 2023). California, Baden-Württemberg, Scotland, and Catalonia stood out in our analysis as U2C members with particularly high and sustained levels of climate policy effort. These jurisdictions share a similar combination of economic, social, and political factors that predisposes them to higher climate policy effort.
The varied outcomes challenge our initially deterministic narratives about climate leadership. Founding membership neither guarantees sustained leadership nor precludes later joiners from ambitious action. For instance, structural advantages like renewable resources or economic strength prove insufficient without political commitment. These findings underscore the importance of understanding subnational climate action as embedded within specific contexts rather than as responding uniformly to transnational dynamics (Dubash, 2021). Nonetheless, transnational collaboration and leveraging favorable domestic conditions also matter.
As climate governance increasingly depends on subnational implementation, these insights become crucial for developing more effective approaches to climate governance which accelerate GHG emissions reductions (Boasson et al., 2025). Rather than assuming uniform ambition or capability, effective multilevel strategies must account for the fact that constitutional variations, political dynamics, and economic structures all shape subnational action. The U2C and similar networks can facilitate learning and legitimacy but must also recognize their limitations in overcoming domestic constraints. Future climate governance architectures should therefore emphasize flexible, context-appropriate approaches that enable diverse pathways toward shared objectives while acknowledging the persistent challenges revealed by this comparative analysis.
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