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npj | urban sustainability Perspective

Published in partnership with RMIT University

https://doi.org/10.1038/s42949-024-00168-7

Towards a public policy of cities and

human settlements in the 21st century

Check for updates

Felix Creutzig 1,2 ,SophiaBecker 1,3,PeterBerrill

1,2, Constanze Bongs4, Alexandra Bussler1,5,

Ben Cave6,SaraM.Constantino

7,8,MarcusGrant 9, Niko Heeren 10, Eva Heinen 10,11,

Marie Joseﬁne Hintz 1,2,12, Timothee Ingen-Housz13,EricJohnson 14,NinaKolleck

15,

Charlotte Liotta1,2,16,SylviaLorek

17,GiulioMattioli 11,LeilaNiamir

18, Timon McPhearson 19,20,21,22,

Nikola Milojevic-Dupont 1,2, Florian Nachtigall1,2,KaiNagel

1, Henriette Närger1,2, Minal Pathak 23,

Paola Perrin de Brichambaut13, Diana Reckien 24, Lucia A. Reisch 25, Aromar Revi26,

Fabian Schuppert15, Andrew Sudmant 27, Felix Wagner 1,2, Janina Walkenhorst 15, Elke Weber 8,

Michael Wilmes 1, Charlie Wilson18,28 & Aicha Zekar1,29

Cities and other human settlements are major contributors to climate change and are highly vulnerable

to its impacts. They are also uniquely positioned to reduce greenhouse gas emissions and lead

adaptation efforts. These compound challenges and opportunities require a comprehensive

perspective on the public policy of human settlements. Drawing on core literature that has driven

debate around cities and climate over recent decades, we put forward a set of boundary objects that

can be applied to connect the knowledge of epistemic communities and support an integrated

urbanism. We then use these boundary objects to develop the Goals-Intervention-Stakeholder-

Enablers (GISE) framework for a public policy of human settlements that is both place-speciﬁc and

provides insights and tools useful for climate action in cities and other human settlements worldwide.

Using examples from Berlin, we apply this framework to show that climate mitigation and adaptation,

public health, and well-being goals are closely linked and mutually supportive when a comprehensive

approach to urban public policy is applied.

Climate action is commonly considered to be designed and coordinated at

the global or national level. However, the discourse increasingly points

towards the downscaling of climate action, with the local level and its

actors as crucial points of intervention. Action will affect everyone, and

everyone will need to contribute to it: climate action is by and for people.

Over half the world’s population (and growing) live in cities1, making

urban-scale policy, research and practice central to progress on climate

change. Still, many solutions for the design, building, retroﬁt, and use of

urban environments often overlook the perspective of people, lack

interdisciplinary integration, and fail to coalesce into comprehensive

policies. Additionally, there is a notable absence of robust models for

extrapolating solutions. When one city successfully implements a climate

solution, how best can insights and procedures be transferred to other

locations in different legal, geographic, ecological, socio-economic, and

cultural contexts? Many cities lack capacity for research and planning and

would beneﬁt from tools and knowledge already available in other cities,

while still matching the local setting. To advance climate action, societies

need a coherent public policy of cities and human settlements that takes

into account local context through a case-by-case approach while none-

theless being scalable and transferable2,3.

Such an endeavor is supported by strong insights from different

literatures and assessments. The Intergovernmental Panel on Climate

Change (IPCC), for example, has considered the urban perspective in the

last two assessment cycles4,5. Calls for an integrated urban sustainability

science have been repeated6–8, and the contribution of various disciplines

have been identiﬁed9. As a result, insights into mitigation and adaptation

in cities have been accumulated and synthesized. The World Health

Organization has been increasingly engaging with health in cities since

Habitat III10 and recently published a joint guide with UN-Habitat

focusing on many health and climate co-beneﬁts indicating how public

health practitioners at national and city level can act locally11. However,

what is still lacking is guidance on how to integrate these insights into a

public policy12.

A public policy of cities and human settlements that brings a social

perspective to technical solutions should consistently integrate climate

action, public health, well-being, and digitalization goals13. The Covid-19

A full list of afﬁliations appears at the end of the paper. e-mail: creutzig@mcc-berlin.net

npj Urban Sustainability | (2024)4:29 1

1234567890():,;

pandemic demonstrated the relevance of urban-scale action for dealing with

thepublichealthcrisiswhileatthesametimeactinginaccordancewith

climate mitigation and adaptation goals14–16. The recent UN World Cities

Report calls for a “new social contract”with universal basic income, health

coverage, housing, and basic services to make cities more resilient17.How-

ever, climate action often takes a backseat to pressing development and

growth needs, especially in cities worldwide. This is particularly prevalent in

the Global South, where urban growth is largest and where climate action is

mostly seen as a co-beneﬁt of development and equity, aligning with the

overarching goal of achieving well-being for all18,19.

The aim of this perspective is to develop a transdisciplinary framework

for urban public policy in the context of climate change and connected

sustainability challenges. We use ‘urban’here to include other human set-

tlements. With this framework, we aim to bring all relevant and concerned

disciplines together, speciﬁcally motivated by making both technical, social

and scientiﬁc knowledge directly relevant to municipal policies. For this, we

set out why the goal of urban public policy, while concerned with climate

change, should be to enable a wide array of functions that support well-being

(‘for people’), including access to health, education, clean water, sanitation,

recreation, social belonging and community, and also to foster agency (‘by

people’). This multi-layered complexity requires different disciplinary

perspectives bound by a transdisciplinary process20 that includes: orienta-

tion knowledge (state of urban governance and greenhouse gas emissions,

and normative goals such as carbon neutrality); systems knowledge

(empirical evidence and understanding of how urban systems work);

transformation knowledge (understanding of interventions that realize the

goals); and process knowledge (methods and procedures of transdisci-

plinary research) (Fig. 1)21,22. We adapt this transdisciplinary framework

for urban public policy research and implementation by ﬁrst confronting

the challenge of delineating proper boundaries of analysis. We then explore

the role of pragmatic mayors and policy experimentation for resolving

the challenging or even ‘wicked’problems of urban sustainability, before

applying the adapted framework in detail, drawing on three case studies

from Berlin.

Realizing trandisciplinarity in the context of epistemic

diversity

A public policy of human settlements requires and is characterized by high

complexity arising from diverse, and often contested goals, interests, values

and models of stakeholder collaboration23. While climate change has been

described as a wicked problem, the intellectual origin of the con-

ceptualization of a ‘wicked problem’can be traced to experiences with the

complex interrelationships between various social and environmental

aspects of city planning24. The urban spatial dimension adds two additional

levels of complexity. First, it is difﬁcult to appropriately identify and address

the relevant scale of analysis when implementing policy at anything larger

than the building scale, i.e., street, neighborhood, district, town, city, city-

region. Second, character and location vary widely in settings from city

center, suburban, peri-urban, mixed-use, single-use, tele-connected areas. It

matters how stakeholders, analysts and participants handle this complexity,

which issues academics investigate in their research, and how municipal

agencies integrate climate action in their administrations and coordinate it

with other governance levels, and which procedures they follow when

doing so.

The complexity of making decisions on environmental issues has been

understood and lucidly analyzed more than 50 years ago, exempliﬁed by the

case study of the Tocks Island Dam13 led by Robert Socolow. This

demonstrated that various perspectives need to be considered to develop a

comprehensive picture of what sustainability means. By necessity this

transcends the evaluation framework of any speciﬁcdiscipline.Sincethen,a

body of literature has evolved around the concept of transdisciplinary

research, outlining key characteristics of wicked problems and procedures,

and the knowledge categories needed to resolve wicked problems.

Examples of advanced water and sanitation engineering25,urban

planning and architecture26, and advanced scholarly and religious

installations27 point to sophisticated urban governance dating back to

antiquity. However, the contemporary urban disciplines on which a public

policy of settlements depends merged in the ﬁrst half of the 20th century.

The foundations of urban ecology and its core tenets can be traced to

the work of sociologists at the University of Chicago in the 1920s28.Applying

concepts from ecology and sociology to the study of cities, authors including

Burgess, Park, and McKenzie seeded the concepts that are now socio-

ecological resilience, ecosystem services, complex adaptive systems, and

social-ecological systems29,30.

Snow’s pioneering epidemiological work deciphering an outbreak of

cholera in Victorian era London dates to the mid 19th century31. Empirical

methods developed most rapidly, however, following the ‘avalanche of

printed numbers’in the years after WWII32. The legacy of this work can be

seen in contemporary quantitative geography (e.g.33,) and in economists’

work on ‘New Economic Geography’(e.g.34,). The statistical physics of the

urban that has developed in the last 20 years can be seen as extending the

epistemological frameworks and methodological practices developed by

urban economists and geographers35,36.

Engaging with the new structures of government and governance

emerging in urban areas, authors including Dahl, Jacobs, Stone and Castells

were key contributors in the middle of the 20th century to the development

of concepts and ideas at the core of contemporary urban geography and

politics literatures. Castell’s“Network Society”37, for example, developsideas

around coordination and communication between actors, differentiated

capacities, fragmented authority, and political and legal contexts that can be

seen today in authors applying multi-level38,39, adaptive40,andpolycentric

governance framings41.

Socio-technical and environmental transitions authors (e.g.42–45,) can

trace foundational ideas in their work to the sociology of technology, sys-

tems theory, and evolutionary economics. Urban ecology and sustainability

science has increasingly embraced a holistic social-ecological-technological

systems (SETS) conceptual framework for urban systems46,47.

This cursory exploration of the ﬁelds that developed an urban focus in

the 20th century provides insight into the siloing of knowledge and practice

in urban research, created by the arrival of arrived established academic

Fig. 1 | Systems, orientation, transformation, and process knowledge are gen-

erated and applied in transdisciplinary processes. Transdisciplinary research

builds on interdisciplinary and multidisciplinary research. Systems knowledge

involves empirical and theoretical studies spanning the spectrum from the speciﬁc,

disciplinary understanding of a single phenomenon to an integrative, inter-

disciplinary perspective on complex relationships between phenomena. Orientation

knowledge is the formulation and justiﬁcation of the goals and objectives of social

change processes. Transformation knowledge involves the understanding and

development of technical, economic, legal, social, and cultural means to reach the

desired goals or objectives. Process knowledge consists of the methodologies and

procedures needed to design and carry out transdisciplinary research. Moti-

vated by21.

https://doi.org/10.1038/s42949-024-00168-7 Perspective

npj Urban Sustainability | (2024)4:29 2

disciplines. Even as urban areas shifted from being the setting to being the

subject of research, each discipline brought with it certain cultures of

knowledge generation48.

The urban ﬁeld has thus had long-established practices, concepts, and

methodologies built into its subject from a range of epistemic communities.

These foundations helped accelerate its development but the same epistemic

diversity served as a barrier to the integration of knowledge across the

intersection of concepts, approaches and methods. This is evidenced by the

“exclusionary discourse”that has been applied to differentiate new from old

contributions to urban literature49.

A framework that enables constructive communication between these

different epistemic communities is still missing. Such a framework can be

utilized critical for urban transformation in the context of transformations

climate action. Here we set out how boundary objects in our novel Goals-

Intervention-Stakeholder-Enablers (GISE) framework ﬁll this gap.

Aboundaryobject approachtoan urbanpublic policyof

the 21st Century: The GISE framework

Boundary objects are, i.e., concepts that can bridge gaps between social

worlds or communities of practice. They can facilitate cooperation without

necessitating consensus on every aspect of knowledge or methodology50.In

essence, boundary objects are ﬂexible enough to be interpreted differently by

various communities but possess enough immutable content to maintain

integrity.

Boundary objects are already widely applied in urban environmental

and climate analysis. For example, climate models and projections function

as tools for synthesizing complex data into actionable insights for urban

planners and policymakers. Geospatial data and Geographic Information

Systems (GIS) visualize spatial impacts of climate change, facilitating a

shared understanding among diverse stakeholders of infrastructure vul-

nerabilities and adaptation needs. Frameworks for urban resilience and

adaptation emerge as conceptual boundary objects, offering a common

language for developing strategies that enhance the capacity of urban sys-

tems to withstand climate disturbances.

Here we suggest four domains of crosscutting knowledge that can serve

as boundary objects. Orientation knowledge provides a normative frame,

delineating the overarching goals and values that guide public policy and

urban planning efforts towards sustainability and resilience. Orientation

knowledge acts as a boundary object by encapsulating shared objectives such

as carbon neutrality, enhanced urban livability,and climate adaptation. This

knowledge fosters alignment across stakeholders from various disciplines—

ranging from environmental science to urban sociology—by offering a

common vision that informs and motivates speciﬁc action plans and policy

designs.

Systems knowledge brings together the empirical and theoretical

understanding of how urban systems operate. As a boundary object, systems

knowledge includes data and models that describe urban metabolism,

energy ﬂows, and urban heat island effects. By providing a common factual

basis, systems knowledge enables collaboration between engineers, urban

planners, ecologists, and policymakers. It helps translate complex urban-

climate dynamics into actionable insights, facilitating the identiﬁcation of

vulnerabilities and opportunities for intervention.

Transformation knowledge focuses on the strategies, technologies, and

practices that can realize the goals set forth by orientation knowledge within

the constraints and opportunities identiﬁed through systems knowledge. As

a boundary object, transformation knowledge bridges the gap between

theoretical understanding and practical application. It encompasses case

studies, best practices, and innovative solutions for climate mitigation and

adaptation in urban settings. By offering a kind of knowledge for validating

approaches for transforming urban systems it enables practitioners and

researchers from ﬁelds such as architecture, transportation planning, and

environmental science to devise and implement effective climate actions

grounded in interdisciplinarity.

Finally, process knowledge concerns the methodologies and proce-

dures for engaging in transdisciplinary research and action, including

stakeholder engagement, policy development, and project implementation

strategies. Process knowledge acts as a boundary object by outlining the

mechanisms through which interdisciplinary teams can collaborate effec-

tively, navigate institutional landscapes, and engage with communities. This

knowledge includes frameworks for participatory planning, collaborative

decision-making models, and governance structures that support urban

climate initiatives. By providing a blueprint for action, process knowledge

enablesthediverseactorsinvolvedinurbanclimateactiontocoordinate

their efforts, ensuring that the process of addressing climate challenges is

inclusive, equitable, and effective.

These four types of knowledge provide a structured approach for

bridging disciplinary divides, fostering mutual understanding, and facil-

itating collective action towards sustainable urban development in the face

of climate change. These domains also imply the importance of assessing: (i)

co-alignment of multiple goals, targets, and pathways across policy domains

such as climate, transport, and health51; (ii) enabling and constraining

contexts, including legal frameworks and regulations, infrastructure, digi-

talization, education, and ﬁnance, that shape the outcomes of policy

implementation52; (iii) governance systems managing diverse actors,

interests, and capacities; (iv) interventions, policy experimentation and

coalition building in support of change. To capture these elements Fig. 2

presents the Goals-Intervention-Stakeholder-Enablers (GISE) framework.

The recent IPCC reports on adaptation and mitigation placed people at

the center of a newly developed Climate Resilient Development

framework53,54. We adapt this people-centric perspective for the urban set-

ting. People are not only stakeholders but also agents of change in shaping

enabling conditions and implementing interventions towards goals that

include well-being and agency, in addition to climate action. Well-being

implies outcome-based justice in seeking to guarantee universal access to

service provisioning systems that reduce GHG emissions and have the

resources and capacity to adapt to climate extremes (cf. relevant IPCC

chapters for both adaptation and mitigation55,56). In turn, agency implies the

active involvement of citizens in contributing to climate resilient and low-

carbon cities. This includes vulnerable people being empowered to exert

inﬂuence on decision-making processes and decisions.

Our transdisciplinary GISE framework contributes to the long-

standing debate about urban climate governance in three ways. First, in

contrast to other frameworks or agenda setting pieces about global urban

science57–59, we directly address public policy of cities. Second, our frame-

work is based on a state-of-the-art understanding of transdisciplinarity21,

thus going beyond the challenges outlined in the literature on urban climate

governance60. Third, our contributions differ from other frameworks on

urban governance and transitions61, through our focus on people, and by

clarifying the four different components of public policy (Goals, Interven-

tions, Stakeholders, Enablers). Other frameworks62 have similar intentions

but a different focus and ignore the role of people in public policy. Our GISE

framework provides practical guidance for active engagement in public

policy of cities in the context of climate change.

Applying the GISE framework to urban public policy on

climate change

An epistemic community on the public policy of human settlements should

work on four interrelated topics: (1) co-creating context-speciﬁcgoalsof

public policy; (2) studying interventions and pathways for reaching these

goals including where possible distributional impacts; (3) understanding

and addressing enabling factors and barriers in the wider institutional and

infrastructural context; (4) involving a wide array of stakeholders and actors

in urban governance (Fig. 2). This approach requires bridging research

across urban-relevant disciplines in ways not yet foreseen.

Co-creating goals

Contributing to the ambition of the Paris Climate Agreement of staying well

below 2 °C warming is an important overarching goal for municipalities. By

2021, net-zero emission targets had been adopted by at least 826 cities and

103 regions54 worldwide. Improved adaptation and resilience to extreme

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npj Urban Sustainability | (2024)4:29 3

weather are also important goals of urban climate governance to ensure the

health and well-being of urban populations. These overarching climate

change mitigation and adaptation goals in cities are strongly related to both

material infrastructures and the digital environment, emphasizing goals

related to digital sovereignty and the governance of urban data. Moreover, to

be effective on the municipal level, climate action goals must be speciﬁed and

worked out for the local context in a co-creative process, including local

actors from politics, civil society, economy and science and following the

principles of transdisciplinarity (see also the section on Stakeholders

below)63.

Goals set ambition; targets guide action and monitor progress. Figure 3

provides three illustrative examples of how climate action goals can be

supported with speciﬁc targets. If relevant stakeholders are involved in the

goal-setting process, the probability is high that they also actively support

the actual implementation of those targets. In addition, this facilitates the

provision of enabling structures. The three examples in Fig. 3draw on

experiences in Berlin and are not representative of cities worldwide; we

discuss the scalability of case-speciﬁc solutions further below.

First, for decarbonizing heat in buildings, a key target is to rapidly

deploy heat pumps as an energy-efﬁcient heating technology that can be

(prohibition of new oil and gas heating) and co-alignment of policies (ret-

roﬁtting to improve the thermal efﬁciency of buildings as a precondition for

effective use of heat pumps). Furthermore, an essential element of reducing

urban GHG emissions in the heat sector is to ensure collaborative efforts

between major stakeholders, in addition to encouraging the businesses and

organizations operating in Berlin to pursuemorestrategiestocutemissions

(via tax breaks and incentive programs) (Fig. 3A).

Second, for decarbonizing transport while promoting public health, a

speciﬁc target is the modal shift away from low-occupancy private cars

towards active, shared, public, and micro-mobility. Interventions include

the provision of safe cycling infrastructure, public spaces for people, and

restrictions or banning of on-street parking (Fig. 3B).

Third, to improve urban climate resilience and reduce peak tempera-

tures, urban planning and government entities must adopt policies and set

targets that increase urban green coverage (e.g., street trees, urban parks,

green roofs) and reduce impervious surfaces. This results in reduced heat

stress and an increase in effective cooling via shadowing and evaporation.

Interventions include city-scale land-use optimization and community

awareness while addressing equity concerns in vulnerable city locations and

among vulnerable populations. Accounting for urban green accessibility

and constraining green gentriﬁcation (i.e. increasing housing prices from

greening projects) are crucial (Fig. 3C).

Co-creating goals on ‘what to do’also requires critical reﬂection on

‘what not to do’. Dismantling resistant elements of incumbent systems is a

critical feature of sustainability transitions64. Negative trends receive less

attention than promising developments, but tackling these trends is key65.

An illustration is the ‘SUV-isation’of cities: rising market shares of big

heavy private vehicles counteract efﬁciency gains in engines and electric

motors. A ban on SUVs may be an integral part of safe, just urban

transport policies that enhance wellbeing. Tourism and airports are other

examples: both are often considered to be outside the realm of urban

climate policies, despite being a major driver ofrising emissions and urban

inequalities (Box 1).

Climate action and resilience goals for cities require wide boundaries of

analysis,asisthecaseforapublicpolicyofhumansettlementsmoregen-

erally. Asking cities to be net-zero or resilient means little if the substantial

needs of city dwellers are not considered in the form of services for sani-

tation, housing and shelter, education, jobs, health, political participation,

social security, recreation, and social interaction. Similarly for climate

adaptation, it is essential to consider wider societal beneﬁts of actions, as well

as trade-offs and conﬂicts with other societal goals66.Whiletherecanbe

conﬂicts with other goals, sound urban strategies should target speciﬁcco-

beneﬁts between adaptation and mitigation67. In addition, giving citizens

agency during the policy-making process can foster ideation and allows for a

more holistic assessment of proposed policies and reduces conﬂicts by

securing societal support for policy interventions.

Well-being has many different constituents, but one dimension above

all has consistently high, beneﬁcial and quantiﬁable effects—health68.For

both climate mitigation and adaptation pathways, health effects will be

considerable69. A few examples: modal shifts to cycling encourage active

mobility, and building and urban design reduces heat stress during heat

waves. The design of green spaces and streets as places for activities results in

urban ecological health that beneﬁts people’s health. Nonetheless, beyond

health there are broader metrics of well-being that provide a basis for

evaluating climate solutions involving infrastructure, social context and

urban living55,56. Demand-side strategies for climate solutions and service

provision in urban contexts have multiple beneﬁts for wellbeing68.Inte-

grating health and climate goals can also help broaden the coalition of actors

and political support for ambitious climate action.

Fig. 2 | The Goals-Intervention-Stakeholder-

Enablers (GISE) framework as an architecture for

the study of public policy of human settlements in

the context of climate change, embedded in

transdisciplinary research. Public policy of human

settlements builds on system knowledge, orientation

knowledge, and transformation knowledge and

relies on and aims to provide process knowledge.

Knowledge creation (downward arrow) starts with

system knowledge and understanding as well as

orientation knowledge, which then induces the

search for goal speciﬁc transformation knowledge.

Action (upward arrow) starts the other way around,

ﬁrst aligning relevant actors and designing con-

textual enabling factors that lead to interventions

that aim to achieve the desired goals.

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npj Urban Sustainability | (2024)4:29 4

Agency addresses the procedural justice dimension of climate resilient

development (‘by people’). While climate change is a complex problem

which partially requires technological solutions, agency calls for the genuine

involvement of affected populations in the policy-making process. Rights-

based approaches focus on capacity-building, meaningful participation in

the policy- and decision-making process—especially for the most vulnerable

groups—and their access to key resources, including ﬁnancing, to reduce

risk and adapt to climate change53. There is a strong relationship between

well-being for all and agency in that service provisioning systems and

infrastructures that underpin well-being (e.g., health, education, air quality,

etc.) provide capacities for people to act. For example, the IPCC speciﬁes

that “investing in universal basic infrastructure, including sanitation, clean

drinking water, drainage, electricity, and land-rights, can transform devel-

opment opportunities, increase adaptive capacity, and reduce vulnerability

to climate-related risks”55. The IPCC assessment also makes clear that social

inclusion for the urban poor relies on process design by local (municipal)

governments55. Agency of people, and in particular of those most affected by

climate change, is a key procedural goal that closely co-aligns with well-

being and health as outcome goals.

Agency not only directly relates to climate governance but also to

indirect governance layers. A particularly important and rapidly emerging

ﬁeld is urban data governance. Digitalization can enable and foster citizen

participation, increase trust by facilitating public audits, and allow for

advanced data-driven policy-making.Itservesasthefoundationforcom-

paring climate risks and policies between cities and for sharing policy evi-

dence. Digital tools are particularly important for developing solutions that

are spatially explicit and adaptable to local conditions, while being scalable

Fig. 3 | Case studies of the GISE framework in Berlin, Germany. A Roll-out of heat

pumps. The share of new residential unit permits in Germany with fossil-based

heating systems dropped from 90% in 2000 to around 26% in 2021, while the share

with heat pumps grew from 1% to 44%138. However, only 2% of homes in Berlin use

electric heat pumps139; mostly in single-family homes140. Further, one quarter of

residential heating systems in Berlin are aged 25 years or older, and the average age is

18 years139. This presents an important opportunity to rapidly replace old fossil

heating systems and increase the use of heat pumps for residential heating. This

needs to be fostered by respective incentives for owners and legislation. While

Germany’s Building Energy Act141 forbids installation of new oil boilers in new and

renovated buildings from 2026, and all newly installed heating systems from 2024

must integrate at least 65% renewable energy where possible, gas heaters may still be

installed as secondary systems or in replacements where heat pumps or district heat

are considered infeasible. Policies and strategies must explicitly exclude oil and gas

from all new buildings and replacements. If fossil heating systems are installed today,

they will become stranded assets, needing replaced long before their technical end-

of-life (e.g. a gas boiler installed in 2025 with a lifetime of 25 years would normally

remain in use until 2050) if climate targets in the building sector are to be met.

B15 min City. A positive urban vision is the 15-minute city that enables citizens to

meet their daily needs within a short walk or bicycle ride from their homes. Inter-

ventions to reach this goal include phasing out fossil-fuel cars, provide affordable

and good public transport, radically reduced on-street parking, which also provides

the opportunity for high-quality active travel infrastructure. This can be facilitated

by changes in the taxation and legal framework at a national level, as well as pro-

viding street space to smart, electric, and active mobility (services) and the infra-

structure these require. This requires the alignment of a multitude of stakeholders;

some obvious (e.g. residents, urban planners, etc.), other perhaps less so (e.g. local

businesses; urban logistics providers). These steps also lead to co-beneﬁts for well-

being and public health in terms of e.g. cleaner air and safer urban space. CHeat

Wave Resilience. Urban communities and infrastructure play an important role in

combating heat stress through representing the enabling factors to reach the desired

climate protection targets. This requires a collaborative effort and interventions of

stakeholders at all levels of society (e.g., urban planners, residents, utilities, housing

sector, and various public corporations). Interventions to reach milestones towards

heat mitigation goals require: (i) Combination of increased urban green coverage

(e.g., street trees, local urban parks, green roofs) and a reduction in the impervious

surfaces cover; either through replacement with vegetation cover or high albedo

material (e.g., car parks and sidewalks) (ii) Identiﬁcation of city vulnerable spots and

population, which are most susceptible to adverse health impacts during heat waves

(iii) Promotion of environmental transport modes (e.g., cycling) along with

investments in providing the required infrastructure (iv) Investments in community

awareness and R&D. Resulting co-beneﬁts will reﬂect on both climate and public

health sector and can support equity in living conditions and accessibility to green

public spaces.

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npj Urban Sustainability | (2024)4:29 5

and transferable to other cities9. However, the data used are often held by

private actors who restrict public access to data and exploit it for commercial

reasons, which are not always consistent with the public good. Here, civil

society and public institutions are key actors in democratizing data gov-

ernance and redistributing the value generated by citizens’personal data70.If

public institutions do not take action, the dependence on private companies

will continue to grow, with progressing lock-in effects, making it increas-

ingly difﬁcult to shape use of data towards public good, strengthen data

sovereignty of citizens, and limit risks associated with unethical data

practices.

Interventions: Pathways Analysis

Pathways analysis is an important means of identifying robust and effective

interventions at given points in time while maintaining the ﬂexibility to

switch to alternative pathways in the future if required. Robustness is

achieved by designing options that: are adapted to local conditions; incor-

porate a social-learning approach that engages citizens; are co-aligned with

other goals such as health and well-being; are strategic rather than reactive.

Robustness also requires adaptive decision making through an unfolding

series of fuzzy moments requiring interpretation and decision-making

under uncertainty42. But this should not be used to sideline critical tech-

nological knowledge. For example, technological analysis reveals that

repeated evocations of hydrogen as a future-proof low-carbo means of

heating homes home is a thermodynamic pipe dream71. Such insights are

crucial to usefully limit the space of reasonable options and so enable

directed action.

Climate mitigation pathways informed by simulation of technological

options and economic costs are numerous72–75 and have emphasized robust

sectoral strategies applicable to cities: retroﬁtting, heat pumps, district

heating, and ﬂoor space reduction in buildings; vehicle electriﬁcation, mode

shifting, and car-free urban planning in transportation. However, while

pathway development is expert-driven and based on scientiﬁc state of the

art, the translation of these pathways into the policy arena requires the

involvement of affected citizens (‘by the people’and not just ‘for the people’).

Climate adaptation pathways are more limited, applied largely to water and

land management problems76–79, large infrastructure projects, and at

national scales80. More locally-scaled adaptation pathways have promoted

vulnerability-based thinking, but with a tendency to justify static solutions

due to legal or other constraints81.

Aﬁne-grained understanding of such pathways needs to involve

perspectives from a diverse set of stakeholders with a focus on key practi-

tioners, as well as different tools, and disciplines (‘by people’)82. For build-

ings,thisincludesarchitectsanddesigners, landscape planners, urban

development professionals, building engineers and real estate analysts as

well as households and citizens. Cross-disciplinary tools include bottom-up

studies83 that inform context-based, empirically-rooted agent-based

modeling84 for understanding behavioral and lifestyle changes in the context

of social dynamics and other contextual enablers and barriers. Speciﬁc

disciplines further contribute detailed insights. For example, urban eco-

nomics reveals the interplay between marginal prices and urban form, and

the relationship between transport infrastructure and settlement patterns85.

Sectoral or disciplinary investigations must be supported by integrated

urban planning, and by social studies that inform pathways with insights on

distributional effects, cultural constraints, and value conﬂicts. Pathways

explicitly allow dynamic interaction effects between implementation stra-

tegies towards speciﬁc or sectoral targets to be considered (e.g., the efﬁciency

of heat pumps improves with more energy-efﬁcient housing stock).

Pathways analysis also helps to evaluate the well-being co-beneﬁts of

climate action (‘for people). For public health, health equity is an important

concern. Pathways also need to consider possible adverse consequences for

some groups, e.g., considering the accessibility of ‘fuel poor’(those depen-

dent on cars but with little income), and liquidity constraints of home-

owners transitioning to heat pumps. Adverseoutcomesforhealthequitycan

arise in several ways, including through population displacement due to

gentriﬁcation following area-based urban greening investments86,87.How-

ever, well-designed and allocated green space in the city can help avoid

trafﬁc for recreation outside cities, provide space for interaction and

exchange, and reduce social inequality if accessible to citizens disadvantaged

throughage,healthorincome

88.

Pathways of digitalization and its impact have been conceptualized89,

but not yet investigated at anurban scale. Theavailability and applicability of

data for urban climate governance is an important ﬁeld for further inves-

tigation, as interactions between the digital and material worlds are playing

an increasingly inﬂuential role in pathways towards climate and other goals.

This is especially relevant when it comes to monitoring and evaluating the

implementation of climate action interventions towards established

sustainability goals.

Stakeholders

Urban governance is multi-level, multi-actor and polycentric90.Typically,

governance of cities starts with national legal frameworks, may involve

region-speciﬁc regulation, has mayoral decisions at its center, includes

district management, and involves various forms of direct citizen, civil

society, and business participation. The agency and coordination of stake-

holders, and in particular urban citizens, are therefore integral to a public

policy of human settlements (‘by people’).

Municipal leadership and municipal executive bodies are paramount

for urban action (Box 2). Although cities are more limited in legislative scope

than national or regional bodies, they have certain governance advantages.

For example, cities can more easily run policy experiments91 while acting at

an intermediary level to generate trust among citizens and ﬁrms in support

of collective action92.

Civil society plays an important role in urban climate action due to

spatial proximity and shared experiences (‘by people’). Cities tend to be the

Box 1 | Limit urban airport capacity

Aviation emissions have soared, and now account for around 2% of

global greenhouse gas emissions. Technological solutions to providing

low-carbon ﬂight remain distant promises142. Although air travel mostly

happens outside cities, much of it has cities as origin or destination.

Residents of large cities have comparatively high emissions from air

travel after controlling for socio-economic factors. The reasons for this

are multiple but likely include an induced demand effect from better

accessibility to large airports143,144. City tourism is one of the fastest-

growing tourism segments and its climate impact, though typically

overlooked, can be substantial. Locally adverse impacts are not dis-

tributed equitably145.In‘international’cities like Brussels and Barcelona,

the estimated climate footprint of inbound air travel for city tourism is as

high or even higher than the ofﬁcial climate footprint of local residents for

all purposes145,146. This could be substantially higher in developing

country cities. Many cities actively contribute to these trends by pro-

moting airport expansion through ‘city-marketing’strategies that are

reliant on tourism inﬂows from distant locations. An effective policy for

climate mitigation requires a rethinking of aviation, e.g. via limiting airport

capacity expansion. To make these initiatives economically viable,

marketing campaigns and tourism strategies—often enthusiastically

endorsed by city mayors—could move from short-stay tourism to slow

travel concepts and an expansion of night-train capacity in regions with

enabling railway networks.

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sites of protest, resistance, and demonstrations as manifestations of social

opinion, and activism. This characteristic strengthens the link between who

(citizens) and how (support desirable decisions and resist undesirable

decisions). Examples of such resistance include globally networked social

movements such as Fridays for Future, which are organized into sub-groups

across various cities and have developed site-speciﬁc demands. For example,

the channeling of civic frustration about missing safe bicycle infrastructure

in Berlin led to a referendum and then a new mobility law at city-regional

level93.

Administrations particularly in countries that operate under civil law,

are tasked with following rules, regulations, and processes that may cause

tension with the emerging imperative of climate action, which has only

started to be codiﬁed into law and procedures. In Germany, administrative

rules governing street spaces mandate lengthy procedures and protocols for

even small modiﬁcations towards sustainable transport modes or livable

neighborhoods. In the US, the California Environmental Quality Act is

misused to prevent low-carbon housing projects, including in-ﬁll develop-

ments and multi-unit residential buildings. Hesitant administrations can

use codiﬁcation to block climate action endorsed by municipal leaders

(Box 3). In other cases, municipal administrations have been hollowed out

by national centralizing tendencies leaving municipal entities with insufﬁ-

cient powers, human resources, and ﬁnancial capacity to undertake inde-

pendent action.

Businesses, service providers, and skilled trades are other important

stakeholders. For example, business operatives can both sell and supply the

most resource-efﬁcient products and services by default94. Trades people are

required to implement technological solutions such as heat pumps (Fig. 3A).

Associations and unions are central to promoting (re-)education and ups-

killing of workforces to exploit the opportunities inherent to net-zero

transitions.

Coordination and collaboration between departments and govern-

ment levels are essential for good urban governance. Given the complexity

of administrations themselves, effective governance is therefore a multi-

dimensional process, in which top-down, bottom-up and ‘middle-out’

processes mutually inform and nourish each other95. For example, countries

with national legislation that requires cities to develop climate plans foster

urban climate planning and action96 particularly when national or supra-

national framework documents provide guidelines for action at lower levels

of government97. National sectoral policies, e.g., on vehicle ﬂeet electriﬁca-

tion, have an outsized impact on urban GHG emission pathways. In the

Box 2 | Pragmatic mayors and experimenting as action

Mayors and municipal leaders can make the difference in advancing

urban goals. In Bogotá, mayors Antanas Mockus and Enrique Peñalosa

transformed the city by opening public spaces, increasing accessibility

with bus rapid transit, and improving safety. In Copenhagen, the dedi-

cated ‘bike mayor’Ayfer Baykal led the transformation of urban transport

infrastructure. In Paris, Anne Hidalgo transformed the urban environment

by providing space for people. These mayoral leadership examples were

enabled by focusing on speciﬁc places - a considerable advantage in

urban climate action. By knowing and experiencing the concrete issues

of a place, municipal stakeholders can better work towards viable solu-

tions. Urban policy-making is pragmatic, not ideological, and mayors

need to deliver on the ground, not by winning sophisticated political

arguments. Their constituents care more about their daily infrastructure

functioning, and less about positions along an ideological spectrum. By

working on the nuts and bolts of physical infrastructure, it is possible to

make progress in the ‘thick’context of conﬂicting values, diverging life-

styles and urban living147.

Experimentation and iterative learning are good ways to make nimble

decisions that can be adaptive to changing circumstances148. Research

on urban governance on climate change points towards lived experi-

ences as a key means to deal with the open-ended process of resolving

the wicked problem of urban climate change mitigation and

adaptation149. Trying things out is also a way to improve the social

acceptability of policies, including climate policies. An example is the

Stockholm congestion charge150, initially implemented for a 6-months

trial and then permanently reintroduced. Through large observed beneﬁts

from the policy, positive media coverage, and familiarity of households

with the policy and its impacts, the 6-months trial led to a change in public

opinion from hostile ex ante to favorable ex post. During the Covid-19

pandemic, cities experimented with pop-up bicycle infrastructures,

providing an effective niche innovation151. Similar shifts in public opinion

from initial scepticism towards a new policy to a subsequent embracing

of the policy only months later have been shown in many other contexts.

Examples range from public health (a smoking ban in public places in

New York City) to climate change mitigation (one of the ﬁrst carbon taxes

in British Columbia) to air pollution and trafﬁc management (congestion

charging in London). Numerous psychological theories including status

quo biases and endowment effects predict such reversals152. Providing

opt-out clauses allowing contentious policies or commitments to sub-

sequently be rejected is another good design feature of experimental

policy changes148 to avoid ex ante concerns blocking change153. Con-

ceptualizing changes in policies and behaviors as temporary and rever-

sible experiments helps allay ex ante concerns and allow for positive ex

post experiences of improved results.

Box 3 | Barriers for urban climate governance inside municipal administrations

City administrations are complex organizations that have a key role in any

transformation process towards more sustainable living. Often pro-

cesses are hindered by four factors:

A. A general culture of risk aversion leads to negative or slow decision processes.

Decisions must be escalated to the highest levels, which often means the

politicians154.

B. Conﬂicting directives must be balanced. For instance, cities often strive to create

new affordable housing, which contradicts the mandate to reduce emissions in

the construction sector. Resolving these conﬂicts is difﬁcult and again requires

escalation.

C. City administrations need to cover all areas of urban life, making it important to

interact with many different internal stakeholders. This makes processes lengthy,

and requires a range of governance capacities that may be lacking155.

D. Resources and competences can be limiting. Cities dependent on central gov-

ernment allocation of general taxation are exposed to major political and bud-

getary risks outside their control. In the UK, for example, ﬁscal austerity imposed

by national government following the 2007–2008 global ﬁnancial crisis has seen

local authority budgets cut by 40% on average156.

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absence of national frameworks, international climate networks are fre-

quently used as knowledge and information tools in a more horizontal, city-

to-city approach, supporting cities and other settlements in developing local

climate plans98. Cities in multiple networks perceive themselves, and are

perceived by others, as leading actors of change towards a climate-resilient

future. The 100 cities of the EU Mission on “Climate-Neutral and Smart

Cities”is a good example. The Climate Emergency Declaration movement is

a bottom-up form of collaboration driven by cities and local municipalities

as a call for action to higher levels of government to accelerate climate

action99.

Urban data governance is an increasingly important domain for urban

climate governance. It provides new opportunities for co-design between

urban planners and software engineers (Box 4). With the availability of big

data on infrastructures and their usage, how urban data are collected, shared,

and applied to advance climate action in cities requires effective data gov-

ernance and regulation in the climate-friendly conﬁguration of spaces and

places (e.g., Box 5). This is a new layer of governance in the urban realm

which for millennia has been focused on the governance of physical spaces

of buildings, transport, and utility networks through which services of

housing, mobility, and sanitation have been provided.

Enabling factors

Climate action is not a direct consequence of decisions made by an opti-

mizing ‘social planner’but rather depends on a multi-actor decision

environment and circumstances that advance or hinder implementation.

People in their diverse roles, for example as professionals (urban and

transport planners) and as citizens, play a central role in shaping enabling

factors (‘by people’). These contextual enablers and barriers can be cate-

gorized into infrastructure, data, education, ﬁnance and law.

Physical infrastructure is particularly relevant for urban governance in

a spatially explicit action arena. In a city of spaces and spatial structures,

decisions are not made in the abstract, but always concern one or more

speciﬁc sites such as a neighborhood, street or building. Infrastructures also

play a key role in urban transport. For example, a modal shift away from

private vehicles to cycling requires safe cycling infrastructures (Fig. 3B).

Addressing protection from heat waves with green and blue infrastructures

requires a spatial consideration of parksandtreeprovisionaswellastheir

design to address both climate and just well-being outcomes (Fig. 3C). For

example, parks designed around cultural and social activities are empirically

associated with less gentriﬁcation and more just outcomes than those

designed around recreation and aesthetics100.

Digital infrastructure is rapidly emerging as a complement to physical

infrastructure. For cities, big data tools support the identiﬁcation of locations

for individual housing units to be retroﬁtted with the most climate miti-

gation beneﬁts at least cost9. Combined with social data, digital tools can also

help identify where urban greening and community development can best

combat distributional inequity in housing. Digital twins that create virtual

simulations of physical systems enable optimal resource allocations and safe

Box 4 | Data governance in cities

Data governance plays an increasingly important role for climate action in

cities. Currently, there are unequal data sharing arrangements between

the public and the private sector. For example, the public sector openly

shares schedules and occupancy proﬁles of public transport services

with private companies. But very few private mobility operators transfer

any data back to city authorities on their services. Countering this

requires strong public institutions that have the expertise to recognize

data related risks and the necessary resources to initiate change, for

example, by mandating data sharing arrangements across various urban

sectors. As an example, the city of Munich has implemented data sharing

arrangements that allow all e-scooter providers to operate on city infra-

structure as long as they share their data on where the e-scooters are

parked and what trips are made during the day157. This helps the city

effectively govern where e-scooters can be used and supports future

urban micro-mobility strategies. Scaling such examples is constrained by

inadequate data-related expertise and funding in public institutions. This

results in a strong reliance on external consulting that in turn undermines

in-house knowledge in the context of a fast-changing digital landscape.

To effectively wrest back control from large, resource-rich data mono-

polies like Google or Microsoft, increased collaboration across many

cities is required to generate sufﬁcient leverage. Alongside the public

sector, citizens have a crucial role to play, as in many cases it is their

personal data that is powering novel digital solutions. However, current

market norms are that personal data are massively collected, analyzed,

shared, and monetized, with the individual having little understanding or

control over the process. To counter this, a public policy of human set-

tlements should deﬁne an alternative approach for handling citizens’

data. It should embrace digital agency, enable data subjects to control

their digital footprint, and engage in the governance of data to preserve

political agency in society, as successfully practiced in the case of

Estonia89.

Box 5 | Barriers of scalability of citizen science to a coherent governance concept

Urban trees are increasingly exposed to climate change, suffering from

droughts and heat stress. City authorities need to adapt urban strategies

to such climate-induced changes by monitoring the trees’need for water

and sufﬁciently coordinating maintenance. This responsibility does not

remain at the administration level, but also residents want to actively

participate and care for their lived surrounding, and can successfully

contribute to their vitality. Therefore, local initiatives for community tree

watering are emerging. In Berlin, the digital platform ‘Gieß den Kiez’—

Water your district—of the CityLAB intends to connect and coordinate

such local watering communities. The platform maps open data on city

trees and provides a prediction of their need for water to actively engage

the citizens in tree maintenance through a gamiﬁed approach. Citizens

can observe tree-speciﬁc information, coordinate as a community, and

mark a tree as watered. Despite the positive feedback of the community

and extensive media coverage, the citizen-led approach at present

remains insufﬁcient to scalability. Speciﬁc legal barriers on IT-

infrastructure as well as absent human capacity and digital competence

such as inadequate data-related expertise hinder the local city govern-

ment from taking it up to a government-led initiative. The CityLAB func-

tions as a successful intermediary platform provider, taking advantage of

the E-Government law (E-Government-Gesetz Berlin - EGovG Bln)by

using open data and providing it to the public in a visualized platform

approach. This once again outlines the reliance on external inter-

mediaries to bypass legal and educational scaling constraints and the

relevance of explicit human capacity to provide interfacing. It also

stresses the importance of context and stakeholder considerations in

urban settings.

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innovations to be tested ‘in virtual vivo’before being applied to physical

infrastructure101. Remote sensing data combined with ground-truth data

(including through distributed citizen science initiatives) feed high-

resolution maps of urban form and movement that inform agile urban

planning of location-speciﬁc changes to reduce car dependency. In turn,

geo-localized social media data can reveal actions people are taking to deal

with everyday challenges in the urban environment102.Agent-basedmodels

can then combine the big data resolution with insights on the behavior and

choices of city dwellers, informing strategies on where and how to change

mobility systems. Digitalization creates powerful tools for reducing green-

house gas emissions, exempliﬁed by novel data-driven urban planning

strategies103, or by smart and shared mobility options that reduce reliance on

private cars104,105. An increasing collection of new data further ampliﬁes this

potential106. Mature and established data governance capabilities are a

prerequisite for public actors who seek to utilize sensitive data to inform

policy-making107. To democratize data governance and increase trust in

data-driven decisions, open, transparent and privacy-forward processes are

key. Important design principles include data separation, stewardship, and

citizens’control108,109. It is also key to recognize that digital transformations

can often lead to exclusionary impacts for impoverished citizens110–112.

Digital infrastructure should be built and accessed in ways that reﬂect dif-

ferent groups’perspectives and needs. Those lacking the ﬁnancial capacities

or skills to use or engage with new technologies should not be marginalized.

Education is another contextual ﬁeld that can be either enabler or

barrier if it’s a limited resource. Inter alia, skills and training in support of

net-zero goals is a complex, multi-faceted challenge113,114.Berlin,for

example, is lacking the skilled tradespeople, electricians, and construction

workers required for heat pump installation, and the transport planners and

urban designers competent in cycle infrastructure planning. Micro-degrees

and the engagement of the private sector and unions are central to remove

this barrier.

Finance is typically considered a national-level domain but is

central to urban transitions. Cost-efﬁcient low-carbon technologies such

as heat pumps require up-front investments that are prohibitive for

many households. Targeted credit programs are helpful, but climate

action interventions by municipal governments require funding that

largely surpasses their budgetary capacities. This means sustained

national ﬁnancial support for urban mitigation and adaptation policy

implementation.

At the legal level, interdependencies between national and city-scale

governance require alignment between regulations at both levels. District

transport planners in Berlin are hindered by an arcane street regulation

framework that prioritizes car transport over everything else and restricts

interventions to change how street space is allocated and used in alignment

with zero-carbon mobility goals.

Integrating knowledge creation and climate action

Here we tie these public policy elements back in to our transdisciplinary

GISE framework (Figs. 1and 2). At its core, knowledge creation and

advancing climate action are intrinsically interwoven (vertical arrows in

Fig. 2). Stakeholders and professionals involved in realizing the enabling

factors are creating transformation knowledge. For example, information

and global and national mitigation discussions do not always trickle down to

urbanprofessionalsontheground.Academicactorsinvolvedinpublic

climate advisory boards not only communicate scientiﬁc insights but also

serve as impartial agents that can bring other stakeholders with speciﬁc

political or economic interests to the table.

Formats of knowledge creation and co-design processes, such as

decision theaters and experimental games, are simultaneously required to

deﬁne goals and to create both orientation and system knowledge. These

formats advance climate action while simultaneously providing agency to

people. The potential of co-design processes lies intheir capacity to integrate

stakeholders as epistemic partners to create policy solutions and plan their

implementation based on situated knowledge. These processes can facilitate

a way towards publicly acceptable agreements particularly if structured less

around positioning within power systems and more around ﬁnding solu-

tions that work.

Partnerships for developing shared, place-based cases for climate

action provide promising examples that can be followed. Ahmedabad city’s

heat action plan stands out as a unique climate plan in South Asia for various

reasons. The plan co-produced by the Ahmedabad Municipal corporation

in partnership with several actors including academia, international part-

ners, research organizations, and civil society emphasizes an effective early

warning system, capacity building of health professionals, coordination

across key government agencies and awareness initiatives. Over time, the

plan has been well-adopted by the city, reduced heat related deaths and

morbidities and its success led to its replication in several other Indian

cities115. Ahmedabad and other cities, however, face challenges to main-

streaming and scaling up at the city scale such as through climate resilient

housing or mandating climate actions as part of building codes. As another

example, Graz is revolutionizing its climate governance through the

implementation of the Climate Information System Graz. This interactive

platform integrates a wealth of urban climate data sourced from simulations,

measurements, thermal ﬂights, and drone surveys. Serving as a dynamic

hub, the portal not only informs urban planning but also drives organiza-

tional and political decisions. It fosters synergies with existing policy fra-

meworks, facilitates networking among diverse stakeholders across

disciplines, and promotes novel avenues for cooperation and collaboration.

Climate Commissions bringing together public, private, community and

private sector actors have been developed over the last several years in

Durban, Surat, Edinburgh, Leeds, Belfast, Berlin and other cities. They offer

avenues for collaborative climate action116 and experimental governance117.

Climate Commissions may also be able to develop new capacities and

demand for action.

On the other hand, in extreme cases, cities work in an autocratic mode

where top-down imposition plans leads to complete lack of buy-in and

disconnect with the needs of people. Co-design of processes also needs to

involve actors whose primary focus is not climate change. Understanding

cities as a vital human habit for health at individual and population levels

necessarily involves the public health profession. Health practitioners often

have vital data on local health needs and trends and much-needed skills for

wieldingtheevidencebasethroughpolitical advocacy, tied to a professional

ethical position which encompasses health equity. Co-design of processes

involving health and climate actors can thus improve decision-making on

climate-resilient cities.

Scaling solutions

Dating back as far as the development of statistical physics in the nineteenth

century118, scaling urban knowledge has posed a challenge for disciplines

focused on the urban28,119–121. Along one dimension, the challenge of scaling

is the challenge of understanding the extent to which urban knowledge from

one context can be appliedin another (the generalizability challenge). Along

a second dimension, the scaling challenge contends with the extent to which

urban concepts, such as urban capacity, civic pride and the quality of gov-

ernance, can be operationalized in ways that are valuable for urban research

and practice (the replication challenge)122.

Foregrounding people and communities can play an important role

engaging with both these dimensions. The involvement of people and

communities through citizens assemblies123, Climate Commissions124,cli-

mate juries125, and by other means, is critical to the development of a better

understanding of the heterogeneity of cities, to develop urban capacities, and

to realize the social license needed for the rapid scaling of urban-scale

climate action. People and community-centered research practices and

methodologies are therefore critical for addressing the generalizability

challenge. At the same time, the involvement of people and communities via

citizen science movements126,urbanlabs

127, participatory games128,orother

means, can help with the development of place based understanding of

urban concepts, and address the challenge of replicability. Pairing the

information drawn from these analyses with advances in computational

social science129, including the application of deep learning and neural

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networks and boosting103, stacking and Bayesian model averaging130,maybe

key to unlocking rapid advances in urban learning.

Millions of cities exist worldwide, yet only a small minority possess

the capabilities to systematically explore climate solutions. Numerous

cities lack the technical proﬁciency and ﬁnancial means required for

data collection, developing emissions inventories, climate scenarios

downscaling, vulnerability mapping, and the formulation of climate

strategies in alignment with global and national targets. Furthermore,

these cities often face ﬁnancial constraints, relying primarily on funding

from superior government bodies or international sources. A major

challenge is how solutions that are identiﬁed and implemented in some

cities can be adapted and adopted by others with low transaction costs.

There are broadly four approaches in research and practice for tackling

this challenge.

First, comparative analysis, meta-analysis, and synthesis across case

studies allow shared insights and strategies to be drawn out of many dif-

ferent rich and contextually grounded examples. The recent IPCC Sixth

Assessment Report, for example, has a dedicated chapter synthesizing evi-

denceoneffectiveclimateactionfromcities across both Global North and

South4.

Second, data-based investigations across cities use econometric or

statistical techniques to identify generalizable predictors of effective urban

climate action. For example, a study of ‘smart local energy systems’in the

UK for locally balancing renewable energy supply with ﬂexible demand and

storage resources used spatial econometric techniques to identify the skills,

housing stock characteristics, and local authority competencies associated

with successful implementation131.

Third, generalized learning (machine learning) of spatially-explicit

solutions across geography apply big data techniques to identify interven-

tion priorities across large areas. Non-linear machine learning-based clus-

tering approaches enable the identiﬁcationofsimilarcitiesordistrictsatthe

country level132 or globally2,3,133. Learning approaches also enable the iden-

tiﬁcation of energy-relevant properties of the building stock at the scale of

individual buildings for speciﬁcregions

103, and potentially for full

continents134.

Fourth, functional international climate networks of cities foster

knowledge exchange and mutual learning on what works, and can accelerate

transfers of local innovations and policy experiments9.Examplesofthis

horizontal governance among cities include various mayoral networks,

ICLEI - Local Governments for Sustainability, and the C40 Cities initiative.

Also regional climate networks help support capacity-limited municipalities

to exchange learning on successful interventions or to collaborate on

sourcing common project ﬁnance.

Despite progress on all four of these approaches for scalability, a critical

role for future urban research lies in furthering our understanding of the

contexts and conditions that allow for approaches that were successful in

one place to be applied in others. Future research must tackle the twin

challenges of reproducibility and variability. Reproducibility challenges arise

from the contested and qualitative nature of many urban concepts such as

capacity, resilience, sustainability, and accountability. This makes conﬂict-

ing ﬁndings between studies hard to reconcile, and the studies themselves

hard to reproduce. Variability challenges are due to the complexity of urban

areas, their dynamism, diversity, and histories. These challenges impede

broadly applicable patterns and processes that can provide insights across a

wide range of cities. Big data-driven approaches may help tackle both

challenges in generalizing solutions across cities while respecting city-

speciﬁc idiosyncrasies. Here, urban researchers can beneﬁt from advances in

data applications and advanced statistical approaches in other ﬁelds

including sociology, psychology, and the medical sciences that have simi-

larly faced reproducibility challenges135,136.

Towards a public policy of human settlements in the

21st century

Jane Jacobs wrote, “Cities have the capability of providing something for

everybody, only because, and only when, they are created by everybody.”This

is also true for cities in the 21st century. A public policy of human settlements

can support climate action and the substantial sustainability challenge cities

face, if stakeholders and all parts of urban societies co-create goals and

contribute in their various to implementation.

With the ambition to make the substantial task actionable, we suggest

the following three-fold structure to a multi- and transdisciplinary com-

munity advancing a public policy of cities and human settlements in the

context of climate change. First, coordination and cooperation between

planning, engineering, economic, humanities, health and social sciences and

other disciplines is an integral element of a public policy of human settle-

ments. Only a joint understanding of the challenges, as identiﬁed from

starkly different perspectives, can enable resolving problems and hurdles.

Being conscious of the paradigm shift in the context of the climate and

energy crisis, an understanding of reduced energy and material demand and

its implications for policies and urban development, will enable the iden-

tiﬁcation of interventions concordant with climate and well-being goals137.

Second, while each city is different, it is nonetheless important to scale

solutions by adapting procedures across municipalities, and by learning

horizontally (collaboration, networking, comparing) and vertically (big data

pattern analysis). This requires adequate networking institutions and data

governance structures for cities that operate in the public interest. Third,

researchers and practitioners beneﬁt from coordinating urban climate

action, public health, social inclusion and agency. These domains are

dynamically co-developing. Exchange can support the co-alignments of

goals. Here, too, Jane Jacobs’“everybody”has a key role to play in engaging in

social, political, and economic arenas to develop trusted data, housing,

transport, health, and other infrastructures and optimizing their use and

coordination. The “everybody”is needed in the 21st century to put urban

societiesontoapathwaythatisinlinewith reaching global climate goals and

fosters urban experimentation as climate action: the quintessence of our

public policy of human settlements in the 21st century.

Received: 12 January 2024; Accepted: 30 May 2024;

Published online: 24 June 2024

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Acknowledgements

F.C., N.M.-D., F.N., and F.W. acknowledge support from the CircEUlar

project funded by the Horizon Europe Research and Innovative Action

Programme under Grant Agreement No. 101056810. C.W. acknowledges

support from the iDODDLE project funded by ERC Grant Agreement No.

101003083. D.R. has received funding from the European Union’s Horizon

2020 research and innovation programme under grant agreement No.

101036458 (LOCALISED project) and No. 101019707 (RiskPACC project),

and from a JPI Urban Europe Grant, funded by NWO, grant agreement No.

438.21.445. A.B. has received funding from the Portuguese Foundation for

Science and Technology (SFRH/BD/143942/2019).

Author contributions

F.C. put a ﬁrst framework forward. All authors contributed to the

development and ideas and towards writing the manuscript.

Funding

Open Access funding enabled and organized by Projekt DEAL.

Competing interests

The authors declare no competing interests.

Additional information

Correspondence and requests for materials should be addressed to

Felix Creutzig.

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Technische Universität Berlin, Berlin, Germany.

Mercator Research Institute on Global Commons and Climate Change, EUREF 19, Berlin, Germany.

Research

Institute for Sustainability - Helmholtz Centre Potsdam, Potsdam, Germany.

University for Applied Sciences, Karlsruhe, Germany.

Institute of Social Sciences, Lisbon

University, Lisbon, Portugal.

Ben Cave Associates, Leeds, UK.

School of Public Policy and Urban Affairs and Department of Psychology, Northeastern University,

Boston, MA, USA.

Princeton University, Princeton, NJ, USA.

Environmental Stewardship for Health, Bristol, UK.

Norwegian University of Science and Technology,

Trondheim, Norway.

Technische Universität Dortmund, Dortmund, Germany.

Hertie School, Berlin, Germany.

Universität der Künste Berlin, Berlin, Germany.

Columbia University, New York, USA.

Universität Potsdam, Potsdam, Germany.

CIRED (Ecole des Ponts ParisTech), Nogent-sur-Marne, France.

Sustainable

Europe ResearchInstitute,Cologne,Germany.

International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.

Urban SystemsLab,TheNewSchool,

New York, NY, USA.

Cary Institute of Ecosystem Studies, Millbrook, NY, USA.

Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden.

Beijer

Institute of Ecological Economics, Royal Swedish Academy of Sciences, Stockholm, Sweden.

Ahmedabad University, Navrangpura, Ahmedabad, Gujarat, India.

Department of Urban and Regional Planning and Geo-information Management, Faculty of Geo-Information Science and Earth Observation, University ofTwente,

Enschede,TheNetherlands.

UniversityofCambridge, El-ErianInstitute,CambridgeJudgeBusinessSchool,Cambridge, UK.

Indian Institute for Human Settlements,

Bengaluru, India.

Edinburgh Climate Change Institute, University of Edinburgh, High School Yards, Edinburgh, UK.

Environmental Change Institute (ECI), University

of Oxford, Oxford, UK.

New York University Abu Dhabi, Abu Dhabi, United Arab Emirates. e-mail: [email protected]

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