Introduction

As the dominant human habitat and driver of global economic activity, cities are a major source of greenhouse gas (GHGs) emissions [1]. Urban areas are estimated to account for approximately 70% of global carbon dioxide emissions, largely due to concentrated energy demand, transportation systems, buildings, industry, and consumption-related patterns [2]. Emissions vary across cities and regions, and per capita levels can differ substantially across urban, suburban, and rural contexts. These differences are shaped by settlement patterns, infrastructure, mobility systems, and income levels [3]. At the same time, urban populations face escalating health and economic impacts from climate change, including extreme heat, flooding, air pollution, and disruptions to food, water, and health systems [4,5]. To meet the Paris Agreement goal of limiting global warming to 2°C while pursuing efforts to restrict temperature rise to 1.5°C, global emissions must decline rapidly in the near-term and reach net zero by 2050 [6]. Achieving these targets requires coordinated mitigation and adaptation efforts across governance scales, from international agreements to national policies, as well as subnational and local action.

International climate governance frameworks such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement provide the overarching architecture for collective global climate ambition [6]. Within this multilevel governance context, cities are increasingly recognised as critical sites of implementation, experimentation, and innovation [7]. City governments are tasked with simultaneously advancing mitigation efforts to reduce emissions within their jurisdictions and adopting adaptation strategies to address intensifying local climate impacts [8]. These efforts span multiple urban sectors and departments, including energy, transport, economic development, waste management, urban design, housing, and public and community health. They also require collaboration with diverse stakeholders, ideally informed by scientific evidence and local data [9].

While cities are often described as agile actors capable of piloting innovative policies, tailoring interventions to local conditions, and responding quickly to emerging risks, their capacity to act is shaped by political, institutional, and fiscal constraints [10]. In many governance systems, including federal contexts such as the United States, substantial funding for climate action flows from national and state governments. However, key policy levers such as energy supply, large-scale infrastructure, or watershed management remain outside municipal authority [11]. As a result, local climate action often depends on vertical coordination, intergovernmental funding, and policy alignment across levels of government [12]. Under these constraints, city governments must navigate limited jurisdictional authority while pursuing ambitious emissions reductions and implementing adaptation strategies that address local climate risks and community needs.

This paper examines the roles of cities in managing climate change challenges, with a specific focus on the health impacts of climate-related disruptions [13,14]. Climate change is increasing the frequency and intensity of extreme weather events. These events pose serious risks to human health, including respiratory and cardiovascular diseases, infectious diseases, heat-related illnesses, air pollution-related harms, injuries, population displacement, mental health impacts, and growing pressures on food, water, and healthcare systems [14–16]. These risks are unevenly distributed. Health inequities are significant, with disadvantaged and vulnerable populations—including low-income communities and indigenous communities—bearing a disproportionate burden of climate-related hazards, illness, and morbidity. Such inequities are often rooted in historical marginalisation and worsened by limited access to resources and services that could buffer impacts during climate-related crises [17,18]. Communities with limited access to resilient infrastructure and healthcare services are less able to adapt to climate impacts [19]. As a result, inequities in exposure, vulnerability, and access to resources are expected to widen existing health disparities and intensify public health challenges [20,21].

Within this context, city-level Climate Action Plans (CAPs) have emerged as key instruments. CAPs are formal municipal strategies or frameworks that outline mitigation and adaptation goals, priority actions, timelines, responsibilities, and monitoring approaches [22]. Their legal status and scope vary across jurisdictions, but they serve as primary mechanisms for translating global and national climate commitments into locally actionable plans. CAPs and related strategies (i.e., frameworks for urban climate action) offer a potential mechanism to align global and national climate commitments with local contexts and to generate co-benefits for population health [5,23]. Although cities account for a substantial share of emissions, their authority to address all emissions sources varies. Many major sources of GHGs, such as energy production or agriculture, lie outside direct municipal control. Nonetheless, cities retain significant influence over sectors such as transport, land use, buildings, waste, and public space, making them important actors in climate action implementation.

City governments operate at a scale conducive to cross-sector climate action. Urban governance is often more agile than national politics, with city leaders closer to public needs and less constrained by political gridlock [24,25]. In some cases, this agility has enabled cities to adopt more ambitious climate policies, even where national action has lagged [26]. However, this relative agility must be understood within the realities of multilevel governance. Even in national systems, substantial funding, regulatory authority, and policy direction flow from state or national governments. These factors shape the scope, ambition, and feasibility of city CAPs. Cities therefore exercise autonomy within constraints, negotiating competing priorities, budgetary pressures, and political dynamics that influence CAP design and implementation.

Over the past decade, substantial scholarly attention has been devoted to assessing CAP content and quality [26,27]. By contrast, evidence on real-world CAP implementation and impacts remains scarce. This gap reflects several challenges, such as difficulties attributing emissions reductions or health outcomes to specific plans, overlapping policies across governance levels, spillover effects beyond city boundaries, limited baseline data, and constrained evaluation capacity within municipal administrations [28]. As a result, understanding of how CAPs translate from plans into measurable outcomes, particularly for health and equity, remains incomplete [5,29,30].

Transnational city networks have played an important role in supporting CAP development and initiating preliminary CAP evaluations [31]. Prominent groups, such as C40 Cities Climate Leadership Group [32], ICLEI–Local Governments for Sustainability [33], and the Covenant of Mayors (CoM) [34] support local governments with technical and financial tools, while fostering peer collaboration. However, their reach remains heavily concentrated in high-income contexts, with limited engagement in Global South cities due to resource constraints, institutional capacity gaps, and governance challenges [35].

Health and equity must be key pillars of city climate action

We propose an international research and evaluation agenda for city CAPs and related climate strategies that explicitly centres health and equity across all stages of planning, development, and implementation. Building on existing conceptual models, this agenda addresses critical evidence gaps and responds to growing recognition that climate change is a public health crisis [36–38]. Many climate actions—such as promoting active, low-carbon transport or urban greening—offer significant health co-benefits [39,40]. Yet, when health considerations are absent or marginal in CAPs, opportunities to improve health and build public support for climate policies are missed [41,42]. Similarly, without explicit equity considerations, climate interventions may inadvertently exacerbate social and health disparities [43,44]. Poorly designed policies can contribute to gentrification, rising housing costs, or uneven benefit distribution, reinforcing existing inequities [45–47]. A rigorous research agenda on CAPs, integrating public health and equity goals, can reveal current shortcomings and guide more just and inclusive policies.

Recent research has advanced understanding of CAP design, evaluation, and implementation. Frameworks such as the Urban Climate Action Planning (UCAP) model [28], Urban Climate Change Integration Index (UCCII) [30], ADAptation plan Quality Assessment index (ADAQA) [27], the Adaptation Policy Credibility (APC) framework [48], and the Integration of Mitigation and Adaptation (IMA) framework [49] highlight integrated mitigation and adaptation strategies, cross-sectoral collaboration, and alignment with sustainability objectives [27,28,48,50,51]. However, these frameworks often assess mitigation, adaptation, or environmental dimensions in isolation and place limited emphasis on health and equity as cross-cutting, measurable outcomes. While these models increasingly acknowledge public health and equity, more work is needed to systematically incorporate and evaluate these dimensions across CAP development, implementation, monitoring, and evaluation in diverse contexts.

Public health considerations in CAPs remain limited [52]. An international review of 350 city CAPs found that only 35% explicitly mentioned public health, with health departments rarely central to planning [53]. Similarly, an analysis of 400 large cities reported that just 10% of adaptation plans included specific health actions [7]. Given the time elapsed since these studies were conducted, and especially after the COVID-19 pandemic strained health systems, it is unclear whether these patterns have persisted, evolved, or deteriorated. This uncertainty underscores the need for updated research to assess current integration of health in CAPs and the evolving role of public health actors in climate governance. It is also important to examine actions in transportation, land use, food systems, and other sectors for their health effects, both positive and negative, since many health benefits of CAPs are likely to arise indirectly through non-health sectors. Existing evidence suggests these cross-sectoral linkages and associated health impacts are rarely made explicit or systematically tracked.

While many CAPs acknowledge disproportionate impacts of climate change on marginalised communities, few incorporate measurable equity indicators or targeted interventions to reduce disparities [7,42,54]. Future research is critical to address questions such as: to what extent CAPs explicitly include health and equity goals, what barriers prevent their inclusion, what facilitators enable their inclusion, and how these goals influence implementation outcomes. Moreover, little is known about whether health and equity goals are systematically monitored or evaluated over time. Achieving equity in CAPs requires not only fair outcomes but also procedural justice, including transparent and inclusive decision-making processes that ensure marginalized communities actively influence both the planning and implementation of climate actions.

We identify two additional gaps in CAP literature. First, research on CAP implementation and impact is notably sparse, particularly with respect to health and equity outcomes [28,55]. Evidence from practice illustrates these challenges. A 2023 review of 37 Indian city heat action plans found most were not designed for the local context. Only ten established locally defined heat‑wave thresholds, and just two conducted explicit vulnerability assessments [56]. Similarly, in several African cities, the rapid adoption of global green building standards faced resistance because they did not align with local economic realities, highlighting how top-down plans can be constrained by political, institutional, and resource limitations [57].

Second, existing CAP research is heavily skewed toward high-income cities, whereas cities in the Global South, which often face greater climate risks and structural constraints, remain underrepresented [58,59]. Our proposed framework is designed to be universally relevant but adaptable to context-specific governance constraints, acknowledging that institutional capacities, resources, and regulatory environments vary widely across cities. Robust evaluation methods and standardised yet flexible metrics are needed to assess whether CAPs reduce vulnerabilities and health disparities over time.

We address these gaps by proposing an international research and evaluation agenda for city CAPs. This agenda builds on substantial literature evaluating urban climate plans, including frameworks such as UCAP, ADAQA, APC, and IMA, which have largely focused on assessing CAP design and content (what CAPs say) rather than their implementation and outcomes (what they do). Prior frameworks also tend to treat mitigation, adaptation, and environmental domains separately, which can create gaps and overlook important synergies and trade-offs. In contrast, our framework positions public health as a central, cross-cutting lens through which we can advance integrated urban climate policy. This approach provides a socio-political rationale for climate action, strengthens accountability, and enables a more comprehensive assessment of CAP performance and progress.

Rather than proposing another plan-scoring or content-assessment approach, we present a framework to guide research and evaluation across the full CAP policy cycle. Our contribution advances existing approaches in three ways: (1) systematically embedding health and equity as integrative, cross-sectoral dimensions across all phases of the CAP process; (2) emphasising implementation, real-world impacts, and measurable outcomes; and (3) treating public opinion and communication as cross-cutting factors influencing CAP feasibility, durability, and political legitimacy.

We conceptualise research and evaluation as overlapping in methods and goals and present a conceptual model alongside high-priority recommendations. The model was developed through consensus among a geographically and professionally diverse group of authors in climate change, public and community health, urban planning, evaluation science, and equity-focused policymaking. Our aim is to guide policy- and practice-relevant research that strengthens CAP design, implementation, and impact. We want to ensure that health and equity are core pillars of effective urban climate action.

A conceptual framework for city CAP research and evaluation centred on health and equity

Our proposed framework defines five key research areas essential for evaluating and informing CAPs and related city-level climate strategies. It is based on the premise that systematic, inclusive research—aligned with the inter-related policymaking elements of development, content, implementation, and outcomes [60,61]—can enhance CAP quality and increase effectiveness in advancing climate action, health, and equity [62,63]. Communication, public opinion, and stakeholder engagement influence all phases of the model (see Fig 1).

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Fig 1. Conceptual framework for research and evaluation of Climate Action Plans centred on health and equity.

The framework organizes priority research areas across CAP development, content and quality, implementation, and outcomes, with health and equity considerations embedded at each stage. Although depicted sequentially, these stages are iterative: evidence from implementation and outcomes can inform revisions to CAP content and future planning cycles. Public opinion and communication are expected to influence all stages of the process.

https://doi.org/10.1371/journal.pclm.0000891.g001

Our framework begins with CAP development and governance, because the processes of plan creation, including leadership, inclusiveness (e.g., stakeholder engagement), and transparency fundamentally shape CAP effectiveness [64–66]. Development of CAPs also depends on factors that make certain cities more likely than others to pursue climate action. Policy ideas and innovation can spread from one city to another through policy diffusion mechanisms, which may involve learning from peer cities, emulating successful practices, responding to economic competition, or complying with directives from higher levels of government [67].

The second focus is CAP content and quality. Content refers to the mitigation and adaptation goals and actions included in the plan, as well as their alignment with authoritative recommendations such as IPCC guidance [4]. Quality indicators reflect the likelihood of effective implementation, considering goal specificity, responsibility for implementation, timelines, consistency with evidence, evaluation plans, and identified funding sources [68]. Inclusion of health and equity goals and actions is a key quality indicator. While alignment with global recommendations signals adherence to widely accepted standards, high-quality CAPs also incorporate locally relevant evidence, context-specific priorities, and actionable measures to ensure strategies are both feasible and effective.

The third and most essential aspect of CAPs is implementation. Success depends on the presence of actionable plans, sufficient budgets, leadership, partnerships, and robust evaluation and reporting mechanisms [69]. The fourth component is CAP outcomes reflecting how implemented actions translate into increased adaptation preparedness, GHG emission reductions, improved health, and enhanced equity [70]. Assessing outcomes is often the most challenging aspect due to time lags, attribution issues, and data limitations.

Finally, public opinion and communication influence all the components of CAPs. Informing citizens and eliciting their input and support is likely essential for the political viability and longevity of the CAP. While climate action is highly political in many contexts, this is not limited to national or state levels. Local-level advocacy and lobbying can also shape CAP development and implementation. Evidence from some cities shows that interest groups, including supportive advocacy organizations and opposing industries, can influence priorities, and in some cases, public opposition has delayed or altered CAP implementation [71,72].

Identifying CAP research and evaluation priorities

We propose a prioritised agenda for the five research and evaluation topics presented in our framework (Fig 1), which aligns with established policy theories [62,63]. These research recommendations are interconnected yet flexible, allowing exploration individually or collectively, in any order. Several recommendations aim to enhance methods for advancing both scientific understanding and practical implementation of city CAPs. Each Priority Area is briefly described to offer flexibility in study design, measurement approaches, and data availability, acknowledging varying constraints faced by evaluators and researchers.

A critical methodological challenge is disentangling local-level CAP effects from broader national or regional trends. Theoretically, multilevel governance and policy diffusion frameworks can guide the identification of local drivers, barriers, and innovations, distinguishing them from national policy signals [73]. Methodologically, both qualitative and quantitative approaches including comparative case studies, hierarchical/multilevel modelling, and mixed-method triangulation can isolate local CAP dynamics while accounting for broader contextual influences [74].

We emphasize international collaborations to develop and customize consensus measures and methods feasible across diverse contexts, enabling cross-city, cross-country, and cross-regional comparisons. Such collaboration can enhance methodological rigor, incorporate diverse perspectives, and support resource sharing. Standardised and contextually-relevant measures will help cities with limited capacity adopt credible, ready-to-use tools that could, for example, integrate guidance on indicator selection, data collection templates, and analytic protocols, enabling rapid assessment of CAP implementation, health and equity impacts, and mitigation outcomes. Our recommendations are relevant to city CAPs as well as related city documents such as heat plans, disaster preparedness strategies, water infrastructure upgrades, social capital initiatives, and nature-based solutions.

Proposed research and evaluation priorities

Conclusion

Research and evaluation of CAPs are inherently complex, involving multiple city departments and challenges such as data gaps, limited coordination, competing priorities, and the need to integrate CAPs with other planning documents that also address climate-relevant issues, such as master plans, zoning codes, and disaster preparedness plans [7,8,99]. Understanding how CAPs operate alongside or in relation to these documents, and why cities pursue dedicated CAPs despite existing guiding frameworks, is essential for a “whole-of-government” approach to climate action. Resource constraints and heterogeneous climate-related risks further complicate CAP development and implementation. City administrations vary widely in their authority, agency, and competencies. While many wield significant decision-making power over sectors such as energy, transport, building regulations, urban planning, health, recreation, waste, and water, their actions are often constrained by competing budgetary priorities, resistance from vested interests, and limits on municipal authority imposed by higher levels of government.

Priorities and needs also differ by geography, resource availability, and governance structures. For example, some cities must prepare for, or are already experiencing, the impacts of rising sea levels and heavy rains, while others focus on reducing emissions, adapting to extreme heat, drought, addressing declining food productivity, or transforming transport systems.

Even under ideal conditions, building a strong evidence base aligned with this research agenda will take time. However, findings from each research topic can inform local improvements in CAP development, implementation, and revision—especially if results are clearly and broadly communicated to decision makers and stakeholders. Incremental progress can build research capacity, encourage broader evaluation, and accelerate climate action.

We can anticipate some key determinants of success in realizing the recommendations of this research and evaluation agenda. First, funding is critical. Identifying and securing resources for CAP evaluation will be a major challenge. Some cities could support local evaluations in partnership with universities or advocacy groups, while national and international funders—including non-profits and governmental agencies—can help by prioritising CAP research, providing grants, and offering training programs. Ideally, funding would also support networks of city teams to collaborate and share learning, advancing climate action collectively.

Second, interdisciplinary and transdisciplinary collaboration is essential, particularly when research is participatory and driven by communities and their needs, ensuring that CAP evaluation and implementation reflect local priorities, knowledge, and lived experiences. Municipal climate action is deeply political. In Flagstaff, Arizona, local opposition to the 2018 climate plan revealed how shifts in leadership and framing can dilute or overturn CAPs [100]. In contrast, robust engagement as in Oakland, California’s 2030 Equitable Climate Action Plan, generated durable public support through town halls, workshops, and interactive digital platforms [101]. The Future Resilience for African Cities and Lands (FRACTAL) project embedded researchers within city governments and convened officials from multiple sectors to co-develop solutions to pressing local issues [102]. Such participatory and citizen-driven approaches strengthen legitimacy, improve data quality, and enhance equity and accountability.

The recommended research and evaluation topics require diverse expertise—including climate scientists, health researchers from multiple sub-disciplines (e.g., health equity), behavioural scientists, measurement experts, statisticians/modelers, communications experts, qualitative researchers, political scientists, community engagement experts, and dissemination and implementation experts. Not all areas will be needed for every study but given this research agenda’s emphasis on health and equity, teams should include relevant expertise in these areas. Although interdisciplinary collaboration can be challenging, evidence increasingly supports the effectiveness of “team science” [103].

Third, international collaboration and coordination can amplify the impact of local CAPs, despite their local scope. Cross-city and cross-country coordination increases the applicability of methods and tools, facilitates shared learning from successes and setbacks, and enables comparative research that informs both local adaptation and global best practices.

Our recommendations aim to advance research and evaluation on CAPS and improve communication of findings to diverse stakeholders, ensuring results inform better CAP content and implementation. Given the agenda’s international scope, methods for each research topic should balance local applicability with cross-context comparability. Coordination across jurisdictions and contexts will require substantial investment in developing metrics, building capacity, collecting comparable data, conducting comparative analyses, and effectively communicating results.

A driving motivation behind this proposed agenda is the promise of CAPs as locally-driven yet globally-relevant tools for climate mitigation and adaptation. However, the vast majority of CAP research to date has focused on the Global North [58]. More coordinated global research on CAPs can help identify shared challenges, surface innovative solutions, and guide local adaptations to strengthen CAPs, improve implementation, and deliver measurable outcomes. We hope this vision for CAP research and evaluation, with the explicit aim of enhancing CAP effectiveness, attracts the funding and leadership needed to support the ambitious yet essential research priorities proposed here.