Editing IPCC:AR6/WGII/Chapter-6 (section)

== 6.1 Introduction and Points of Departure ==

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=== 6.1.1 Background and Chapter Outline ===

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Cities and urbanising areas are currently home to over half the world’s population. What happens in cities is crucial to successful adaptation (Grafakos et al., 2019). By 2050, over two thirds of the world’s population is expected to be urban, many living in unplanned and informal settlements and in smaller urban centres in Africa and Asia ( ''high confidence'' ) ( [[#UNDESA--2018|UNDESA, 2018]] ). Between 2015 and 2020, urban populations globally have grown by about 397 million people, with more than 90% of this growth taking place in less developed countries ( [[#UNDESA--2018|UNDESA, 2018]] ). Projections of the number of people expected to live in urban areas highly exposed to climate change impacts have also increased, exacerbating future risks under a range of climate scenarios. Rates of population growth are most pronounced in smaller and medium-sized settlements of up to 1 million people ( [[#UNDESA--2018|UNDESA, 2018]] ).

Since AR5, there has been increasing understanding of the interdependence of meta-regions, large, small and rural settlements which may be connected through key infrastructure ( [[#Lichter--2017|Lichter and Ziliak, 2017]] ), including national and trans-national infrastructure investments ( [[#Hanakata--2018|Hanakata and Gasco, 2018]] ). Almost all the world’s non-urban population and its provisioning ecosystems are impacted by urban systems through connecting infrastructure and family and kinship ties, remittances and trade arrangements that influence flows of water, food, fibre, energy, waste and people ( [[#Trundle--2020|Trundle, 2020]] ; [[#McIntyre-Mills--2018|McIntyre-Mills and Wirawan, 2018]] ; Zhang et al., 2019; Nerini et al., 2019; [[#Friend--2018|Friend and Thinphanga, 2018]] ). Many rural places are so deeply connected to urban systems that risks are observed to cascade from one to the other, for example, when drought in arable zones leads to food insecurity in cities, or where flood damage to urban transport infrastructure leads to prolonged isolation of small towns and rural settlements ( [[#Friend--2018|Friend and Thinphanga, 2018]] ; [[#McIntyre-Mills--2018|McIntyre-Mills and Wirawan, 2018]] ). A focus of this chapter is the experience of a range of urban settlements, from small to large, and the connecting infrastructure and formal and informal networks and systems that join them to each other. There are close synergies with Chapters 7 (Health, Well-being and the Changing Structure of Communities) and 8 (Poverty, Livelihoods and Sustainable Development). There are further important synergies with Working Group III [[IPCC:Wg2:Chapter:Chapter-8|Chapter 8]] (Urban Systems and Other Settlements) and the Cross-Chapter Paper 2: Cities and Settlements by the Sea.

Well-planned climate adaptation can have far reaching co-benefits for sustainable development and community well-being (Nerini et al., 2019; Tonmoy et al., 2020). However, the varied success of cities’ responses to the global COVID-19 pandemic underscores how social and economic conditions, built environments and local planning can exacerbate or reduce vulnerability and long-term sustainable, community well-being ( [[#Megahed--2020|Megahed and Ghoneim, 2020]] ; Plastrik et al., 2020; Hepburn et al., 2020; Sarkis et al., 2020).

Many of the significant sustainable development initiatives that have been proposed and implemented in the last five years recognise the critical importance of cities, settlements and key infrastructure in responding to the crisis of climate change (Zhang et al., 2019; Nerini et al., 2019). There is widespread acceptance of the need for far-reaching responses by actors from the local to the global scales to make human settlements and infrastructure more resilient ( [[#UNDP--2021|UNDP, 2021]] ). There is recognition also of the considerable capacity in settlements to meet climate change challenges, if the governance, financial and social conditions are in place (Carter et al., 2015; [[#MINURVI--2016|MINURVI, 2016]] ). And yet the implementation of climate adaptation planning lags behind climate mitigation efforts in urban communities ( [[#Sharifi--2020|Sharifi, 2020]] ; Grafakos et al., 2019; Nagendra et al., 2018).

Since the publication of AR5, there has been rapid expansion in policy, practice and research related to climate change and human settlements. The 2030 Agenda for Sustainable Development (the SDGs) agreed in September 2015, was preceded by the Sendai Framework for Disaster Risk Reduction 2015-30 and followed shortly afterwards by the Paris Agreement (December 2015) ( [[#United%20Nations--2015b|United Nations, 2015b]] ). These make explicit mention of ‘mainstreaming of disaster risk assessments into land use policy development and implementation, including urban planning’ (Sendai Framework) ( [[#UNISDR--2015|UNISDR, 2015]] ). The agreements identify ‘sustainable cities and communities’ (SDG11) and ‘cities and subnational authorities’ (Paris Agreement) as important actors in integrating climate and development goals (Sanchez Rodriguez, Ürge-Vorsatz and Barau, 2018). However not all urban SDGs have measurable targets yet, or data, particularly in regard to children and youth, the elderly and disabled ( [[#Klopp--2017|Klopp and Petretta, 2017]] ; Reckien et al., 2017; Nissen et al., 2020). Clear procedures for linking climate adaptation in communities at all scales to the SDGs is lacking (Major, Lehmann and Fitton, 2018; Sanchez Rodriguez, Ürge-Vorsatz and Barau, 2018).

The New Urban Agenda (NUA) (October 2016), with its focus on housing and sustainable urban development, commits its signatories to building resilient and responsive cities that foster climate change mitigation and adaptation ( [[#United%20Nations--2016b|United Nations, 2016b]] ). This agreement followed the Geneva UN Charter on Sustainable Housing, endorsed by 56 member states of the United Nations Economic Commission for Europe ( [[#United%20Nations--2015d|United Nations, 2015d]] ). The NUA aims to ensure access to decent, adequate, affordable and healthy housing for all, while reducing the impact of the housing sector on the environment and increasing resilience to extreme weather events ( [[#United%20Nations--2016b|United Nations, 2016b]] ). Voluntary, networked action led by cities was also illustrated by a November 2019 call to Mayors and youth climate activists to sign a voluntary pledge in a ‘Race to Zero’ ahead of the Conference of the Parties 26, which included endorsing principles of a New Green Deal ( [[#C40--2019|C40, 2019]] ). Other voluntary, global, urban efforts have been led by the scientific community including the Research and Action Agenda on Cities and Climate Change Science which aims to promote research and reports (Prieur-Richard, Walsh and Craig, 2019).

These collaborative global changes are reflected in the bodies of literature assessed for this report. In AR5, the section on ‘human settlements, industry, and infrastructure’ contained three chapters: urban areas; rural areas; and key economic sectors and services. This chapter covers the full range of human settlements: from small settlements in predominantly rural areas, to large metropolises in both high-income and low-income countries. It also assesses evidence of climate change impacts, vulnerability and adaptation on a range of urban infrastructures, including infrastructure that incorporates socio-economic and ecosystem dimensions (see [[#6.1.3|Section 6.1.3]] ).

This assessment also considers new literature about how enabling environments can support adaptation in ways that are also sensitive to Indigenous knowledge and Local knowledge (see below [[#6.1|Section 6.1]] ), social justice (6.4.3.4)) and climate mitigation ( [[#6.3.5.2|Section 6.3.5.2]] ). It builds on the findings of AR5 which highlighted the concentration of global climate risks in urban areas, the complex causal chains that mediate climate impacts for smaller settlements and rural areas, and the multiple issues shaping and influencing economic sectors and infrastructure. This integrated chapter enables a more detailed analysis of the inter-connected drivers of risk that affect urban people and settlements of different sizes. This discussion also highlights the inter-connections within and between urban areas, and between different types of infrastructure and how these complex relationships accentuate or limit the effects of climate change and the institutional structures that play a critical role in mediating and govern these relationships.

This chapter has five main sections. The first elaborates on changes in the international policy context since 2014, highlighting the implications that this has for responses to climate change in cities, settlements and key infrastructure. [[#6.2|Section 6.2]] is focused on observed and projected climate risks, paying particular attention to the ways in which these are created through processes of urbanisation and infrastructural investment. [[#6.3|Section 6.3]] takes an integrated and holistic approach to an assessment of adaptive actions relevant to key infrastructures (those that form the material basis for resilience in cities and settlements, drive economies and are essential for human well-being). [[#6.4|Section 6.4]] assesses the enabling conditions and leadership qualities associated with adaptation processes that can also meet the equity agenda of the SDGs, to leave no-one behind, including the role of governance, finance, institutions and emerging literature around the limits of urban adaptation.

Case studies highlight how climate and other issues interrelate to create (or reduce) urban risk within and between scales of decision making. They illustrate how multiple levels of governance and formal and informal decision making sectors influence how risk production/reduction plays out across a range of urban contexts and networks.

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=== 6.1.2 Points of Departure ===

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The AR5 conceptualised cities and settlements as complex interdependent systems that could be engaged in supporting climate change adaptation (Revi et al., 2014 8.8.2). Effective municipal governance systems and cooperative multi-level governance supported adaptation action. The AR5 report expressed ''medium confidence'' that governance interventions can help develop synergies across geographical and institutional scales. Urban areas face challenges of infrastructure investment and maintenance, land use management, livelihood creation and ecosystem services protection. AR5 also considered how urban localities can encourage incremental and transformative adaptation, build resilience and support sustainable development. The assessment identified the need for multi-level and multi-partner action in rapidly growing cities where institutions and infrastructure are still not established to meet the growing demands of the cities. However, there was only ''medium confidence'' that adaptation action was happening in the AR5 review period.

The framing of ‘key economic sectors and services’ in AR5 focused primarily on three infrastructural areas (energy, water services, transport) and on primary and secondary economic activities (including recreation and tourism, insurance and financial services). Cities, settlements and key infrastructure are also referred to in the IPCC special reports released since AR5. The Special Report on Global Warming of 1.5°C ( [[#IPCC--2018|IPCC, 2018]] ) examines impacts of global warming on urban systems and infrastructure in the context of advancing sustainable development and eradicating poverty. It highlights the risks facing residents of unplanned and informal urban settlements, many of which are exposed to a range of climate-related hazards (Sections 3.4.8 and 4.4.1.3). The Special Report on Global Warming of 1.5°C also identifies green infrastructure, sustainable land use and planning, and sustainable water management as key adaptation options that can reduce risks in urban areas (SPM C2.4; C2.5), and highlights ‘urban and infrastructure’ as one of four system transitions required to limit warming to 1.5°C to create an enabling environment for adaptation ( [[IPCC:Wg2:Chapter:Chapter-4#4.3.3|Section 4.3.3]] ). Innovative governance arrangements that go beyond formal ‘government’ and political arrangements and that include non-state actors, networks and informal institutions were identified as important in addressing climate change and implementing responses to 1.5°C-consistent pathways (Special Report on Global Warming of 1.5°C [Sections 4.4.1 and 5.6.2]). In addition, the Special Report on Global Warming of 1.5°C mentions, with ''high confidence'' , the climate-related health effects of urban heat islands, urban heatwaves and increasing risks from some vector-borne diseases (illnesses caused by pathogens and parasites in human populations) (SPM B5.2). The report also notes both trade-offs and important co-benefits of sustainable development in pursuit of climate resilient development pathways that achieve ambitious mitigation and adaptation in conjunction with poverty eradication and efforts to reduce inequalities (SPM D6).

The Special Report on Oceans and Cryosphere (SROCC) similarly emphasizes the role governance plays in reducing disaster risk, through planning, and zoning ( [[#IPCC--2019b|IPCC, 2019b]] ). It identifies vulnerability factors such as poverty, which can undermine resilience and sustainable development in urban communities ( [[#IPCC--2019b|IPCC, 2019b]] SPM C3.1,and [[IPCC:Wg2:Chapter:Chapter-2#2.3|Section 2.3.2]] ) The SROCC report shows that the emerging climate-related challenges are impacting the accessibility and availability of vital resources and blurring the public and private boundaries of risk and responsibility (Cross-Chapter Box 3). According to the SROCC report, new governance arrangements are emerging to address these challenges, including participatory and networked structures, and institutions linking formal and informal networks involving state, private sector, Indigenous and civil society actors (Cross-Chapter Box 3). The SROCC report calls for place-specific action because there is no single climate governance panacea for the ocean, coasts and cryosphere (Cross-Chapter Box 3). The SROCC report highlights evidence of the importance of inclusivity, fairness, deliberation, reflexivity, responsiveness, social learning, the co-production of knowledge, and respect for ethical and cultural diversity in climate-related urban decision making (Cross-Chapter Box 3). In addition, the Special Report on Climate Change and Land notes that urbanisation can intensify extreme rainfall events over the city or downwind of urban areas and have can significant consequences for heat island effects on loss of food production, posing additional risks to the food system ( [[#IPCC--2019b|IPCC, 2019b]] SPM A5.3 and Cross-Chapter Box 4 in Chapter 2).

An additional research bridge between AR5 and AR6 was the IPCC Cities and Climate Change Science conference held in Edmonton, Canada, in March 2018 (Prieur-Richard, Walsh and Craig, 2019). This generated a ‘Global Research and Action Agenda on Cities and Climate Change Science’ (Prieur-Richard, Walsh and Craig, 2019), which highlights six topical research areas where more evidence is needed to inform action: finance; informality; uncertainty; urban planning and design; built and green/blue infrastructure; and sustainable consumption and production. These areas are addressed in specific sections of this chapter or as cross-cutting themes. The Cross-Working Group Box URBAN in this chapter provides a linkage with perspectives from Working Group III.

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=== 6.1.3 Terminology and Definitions ===

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This chapter covers both ‘cities and settlements’ and ‘key infrastructure’.

Definitions of ‘urban’ have become more nuanced since the AR5 review with the publication of the OECD report ‘A new perspective on urbanisation’ ( [[#OECD%20and%20European%20Commission--2020|OECD and European Commission, 2020]] ). This report presents two new global definitions of urbanisation reflecting the degree of urbanisation on a continuum of cities, towns and semi-dense areas, and rural areas. The OECD estimates almost half the world’s population (48%) live in cities, while just 24% live in rural areas and 28% live in towns and semi-dense areas (28%). In addition, the OECD report defines metropolitan areas as functional urban areas together with their surrounding commuting zones ‘to capture the full extent’ of a city’s working population. Metropolitan areas account for 54% of total world population, with the OECD estimating that commuting zones representing 17% of the overall metropolitan population, rising to 31% in high-income countries. In the context of these global definitions, this chapter identifies ‘cities and settlements’ as concentrated human habitation centres (along a dynamic continuum from rural to urban) (Murali et al., 2019; [[#Ward--2016|Ward and Shackleton, 2016]] ) (Figure 6.1) that are fundamentally inter-connected to other urban centres and rural areas as nodes within broader networks.

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[[File:9463d3b3559028c57c12ae89b05e6272 IPCC_AR6_WGII_Figure_6_001.png]]

'''Figure 6.1 |''' '''Defining ‘urban’ and ‘rural’ in relation to cities and settlements'''

Key infrastructure is used here to refer to ‘critical nodes and arteries’ that comprise urban energy, food, water, sewerage, health, transport and communication systems ( [[#Steele--2017|Steele and Legacy, 2017]] ; Maxwell et al., 2018; Bassolas et al., 2019). Key or critical infrastructure provides much of the material basis of cities and settlements, as well as the mechanisms for enabling flows of people, goods, data, waste, energy (through urban metabolism processes of consumption and production) and capital, between urban regions and rural areas (Blay-Palmer et al., 2018; Dijst et al., 2018). An overview of this process of ‘planetary’ urbanisation is provided in Box 6.1. The balance of accumulated scientific knowledge on climate risks, impact and adaptation has been generated from studies in large and medium-sized cities of 1 million or more. While these larger cities continue to grow rapidly (UNDESA 2018), settlements of more than 5 million people contain less than a quarter of the world’s urban population, and more than half of the world’s urban residents live in settlements of 1 million or less (Table 6.1). There is a key gap in knowledge, especially concerning urban enabling environments and how smaller settlements can be supported to accelerate equitable and sustainable adaptation in the face of financial and governance constraints (Birkmann et al., 2016; Shi et al., 2016; [[#Dulal--2019|Dulal, 2019]] ; Rosenzweig et al., 2018b).

'''Table 6.1 |''' Proportion of the urban population in different size class urban areas (UN-DESA 2018). Each column indicates the percentage of urban residents in that region living in cities of that size class.

{| class="wikitable"
|-
! Proportion (by region) of urban population living in cities with population size

! Africa

! Asia

! Latin America and the Caribbean

! Europe

! Northern America

! Oceania

! World

|-
| 10 million +

| 8

| 15

| 17

| 4

| 10

| 0

| 13

|-
| 5–10 million

| 6

| 9

| 3

| 5

| 17

| 0

| 8

|-
| 1–5 million

| 22

| 22

| 25

| 16

| 30

| 60

| 22

|-
| 500,000–1 million

| 9

| 10

| 8

| 11

| 13

| 2

| 10

|-
| 300,000–500,000

| 6

| 6

| 6

| 8

| 7

| 11

| 6

|-
| Under 300,000

| 48

| 38

| 40

| 57

| 24

| 27

| 41

|}

This chapter takes a comprehensive approach to understanding ‘key infrastructure’ as expressed in social, nature-based and physical infrastructure. Social infrastructure includes the social, cultural, and financial activities and institutions, as well as associated property, buildings and artefacts and policy domains such as social protection, health and education that support well-being and public life (Frolova et al., 2016; [[#Latham--2019|Latham and Layton, 2019]] ). Nature-based infrastructure focuses on solutions to risk, applying natural assets such as trees or open water, physical infrastructure describes engineering approaches and grey/physical infrastructure refers to engineered assets that provide one or multiple services required by society, such as transportation or wastewater treatment ([IISD, N.D.]; see also Annex II: Glossary).

This approach is based on a framing of cities and settlements as complex systems where social, ecological and physical processes interact in planned and unplanned ways. This chapter therefore builds on the AR5 [[IPCC:Wg2:Chapter:Chapter-10|Chapter 10]] ( [[#Arent--2014|Arent et al., 2014]] ) conception of key economic sectors and services (e.g., energy, water, transport, waste, sanitation and drainage) by positioning these within three major categories of infrastructure: social, nature based and physical (see [[#6.3|Section 6.3]] ). Where adaptation challenges can be responded to by more than one approach, sometimes working together, this is noted (see also Sections 17.2 and 17.4). This approach allows an understanding of adaptation that is not constrained to the administrative boundaries of cities and settlements, but that includes the networks and flows that connect peri-urban communities, metropolitan regions, suburban settlements and more rural places (see Box 6.1). Both formal provision of infrastructure services by government and informal provision by communities and individuals are considered at risk from climate change, as are existing adaptation pathways and actions.

Cities are complex entities where social, ecological and physical systems interact in planned and unplanned ways (Markolf et al., 2018). The complexity of cities, settlements and key infrastructure (Figure 6.2) where multiple functional systems continuously interact makes it difficult to distinguish risks (Box 6.1). The literature often resolves this by offering discrete assessments for specific sectors (see [[#6.3|Section 6.3]] ). This fragmented approach to understanding climate change associated impacts and risks is then reflected also in siloed approaches to risk management and adaptation financing (see [[#6.4|Section 6.4]] ). Recent literature notes that resilience planning has begun to overcome this tendency by presenting climate change impacts, losses and damages, and urban processes, as unfolding together in interacting and cascading pathways (Fraser et al., 2020; Eriksen et al., 2020) (Figure 6.2). The chapter reflects this change in the literature by presenting climate change impacts through a series of risk assessments, including by hazard type, through indirect impacts on health or food security, key infrastructure systems, land use and human mobility, water flows and on structural conditions, such as poverty and justice in the city (see Sections 6.3 and 6.4). In a departure from AR5 we also consider the consequential interactions of climate risks, impacts, adaptation and climate mitigation (see also Cross-Working Group Box URBAN in Chapter 6).

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[[File:11f21bcf861c8a31cd6bae4c55659355 IPCC_AR6_WGII_Figure_6_002.png]]

'''Figure 6.2 |''' '''The interconnected nature of cities, settlements and infrastructure'''

The IPCC 1.5°C Special Report commented that ‘The extent of risk depends on human vulnerability and the effectiveness of adaptation for regions (coastal and non-coastal), informal settlements, and infrastructure sectors (energy, water, and transport) ( ''high confidence'' )’ ( [[#IPCC--2018|IPCC, 2018]] ).We take this statement as a starting point for assessing the risks to cities, settlements and key infrastructure, with infrastructure extended as noted above. Risks from climate change are understood as the product of climate change associated hazards impacting on exposed and vulnerable people and assets (including biodiversity). Adaptation can, in some cases, reduce exposure and susceptibility and enable recovery and scope for transformation toward long-term equitable and sustainable development. Risks describe both present conditions and future prospects. Direct attribution of hazards to climate change remains limited to temperature extremes and sea level rise, though we consider all hydrometeorological hazards as systems associated with climate change processes.

This chapter also assesses conditions supporting incremental and transformative adaptation ( [[#6.4|Section 6.4]] ). Incremental and transformative adaptation are both important but serve distinct roles in the interaction of urban systems, climate risk and risk management, and in advancing social justice, just transitions and climate resilient development (see [[#6.4|Section 6.4]] ). Climate resilient development pathways are an emerging concept in the literature since the AR5 (Schipper et al., 2020). Climate resilient development is an iterative process of systemic change that integrates both mitigation and adaptation efforts (see Annex II: Glossary). Initial studies highlight the way rapid urbanisation and precarious urban housing and land tenure can undermine climate resilient development, while human settlements that are managed to protect housing tenancy and land tenure rights can advance land use planning and social learning while reducing inequalities and vulnerability and enhancing resilient development (Mitchell, Enemark and Van der Molen, 2015; [[#Bellinson--2019|Bellinson and Chu, 2019]] ; [[#Ürge-Vorsatz--2018|Ürge-Vorsatz et al., 2018]] ). The benefits of integrating decision making across scales for climate resilient development is also highlighted in [[#6.4|Section 6.4]] . How households engage with communities and neighbourhoods and larger units within cities, and how cities (both formal and informal) interact with sub-national and national actors is also discussed, as is the role of finance and community-based organisations (CBOs)/NGOs in the governance process.

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=== 6.1.4 Global Urban Trends ===

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Since AR5, many cities and other settlements, particularly unplanned and/or informal in Asia and Africa, have continued to grow at rapid rates (van den Berg , Otto and Fikresilassie 2021). Elsewhere, in Latin America in particular, while growth is less rapid, inequality persists. As a result, cities and settlements are crucial both as sites of potential action on climate change, and sites of increased exposure to risk ( ''medium evidence, high agreement'' ) ''.''

Patterns and trends for urban population growth were described in detail in AR5. Between 2015 and 2020, urban populations globally have grown by more than 397 million people, with more than 90% of this growth taking place in less developed regions ( [[#UNDESA--2018|UNDESA, 2018]] ). The latest population projections from [[#UNDESA--2018|UNDESA (2018)]] reinforce the trends identified previously, with even higher estimates for global urban populations. The 2012 data used in AR5 projected a global urban population of 4984 million in 2030 and 6252 million in 2050; the 2018 revisions project 5167 million and 6680 million respectively. Particularly noteworthy is the higher projection provided for sub-Saharan Africa’s urban population: increasing from 596 million to 666 million in 2030, and from 1069 million to 1258 million in 2050. These figures highlight the continued trend toward larger urban populations, and the particular significance of this in areas which currently have relatively small proportions of their populations living in towns and cities; this is also true in some Small Island States (e.g., the Solomon Islands) (McEvoy et al., 2020). The proportion of the global urban population living in megacities (with populations of more than 10 million people) is expected to continue growing slowly (to 16% of the urban total, or 862 million people, living in 48 agglomerations) by 2035 ( [[#UNDESA--2018|UNDESA, 2018]] ). The size and form of these megacities presents particular challenges with climate change impacts, in areas including air quality (Baklanov, Luisa and Molina, 2016), flooding (Januriyadi et al., 2018), and temperature increase (Darmanto et al., 2019) (see [[#6.2.3|Section 6.2.3]] ).

While there are few analyses of urban trends at the global scale, an additional 2.5 billion people are projected to be living in urban areas by 2050, with up to 90% of this increase concentrated in the regions of Asia and Africa, particularly in India, China and Nigeria, where 35% of this urban growth is projected to occur ( [[#UNDESA--2018|UNDESA, 2018]] ). Growth rates are slowing down in North America, South America and Europe ( [[#UNDESA--2018|UNDESA, 2018]] ). Much global growth continues to outstrip the ability of governments or the private sector to plan, fund and provide for sustainable urban infrastructure and this is most marked in low-income and informal settlements (Angel et al., 2016). Rural migration as a driver of urbanisation is discussed in 6.2.4.3, and literature has documented the way urban expansion and the conversion of agricultural land is also driven by investment incentives and weak planning policies (Colsaet, Laurans and Levrel, 2018; [[#Woodworth--2017|Woodworth and Wallace, 2017]] ). At the same time, early evidence suggests that, at least in some locations, out-migration from cities occurred as a result of the COVID-19 pandemic (Rajan, Sivakumar and Srinivasan, 2020), but the evidence is not clear and in some cases may have increased migration to other megacities (Chow et al., 2021). There is also growing recognition that poor planning has exacerbated the concentrated of deprivation in specific locations, deepening a cycle of exclusion and marginalisation ( [[#UNDESA--2020|UNDESA, 2020]] ).

One critical element of global urban trends which has received growing attention is informality (see also Prieur-Richard, Walsh and Craig, 2019). Informality is one of the key defining features of cities and settlements in the Global South (see Annex II: Glossary; Banks, Lombard and Mitlin, 2020; [[#Myers--2021|Myers, 2021]] ; [[#UN-Habitat--2016c|UN-Habitat, 2016c]] ). In almost all nations in the Global South, more than half the urban workforce work in informal employment; the proportions are particularly high in South Asia (82% in informal employment) and sub-Saharan Africa (66%) (Chen, Roever and Skinner, 2016; [[#Chen--2014|Chen, 2014]] ). The term ‘informal settlement’ refers to urban settlements or neighbourhoods that developed outside the formal system that is meant to record land ownership and tenure and without meeting a range of regulations relating to planning and land use, built structures and health and safety. Informality is a broader concept than ‘slums’, which are usually defined using measures of housing quality, provision of services and overcrowding. While most countries do not generate formal statistics on the number of people living in informal settlements, UN Habitat provides regional and global estimates of the number of urban households that are ‘slum’ households and therefore likely to include most residents of informal settlements. These estimates suggest that there were 1034 million slum dwellers in 2018, including some 56% of the urban population in sub-Saharan Africa and more than 30% of the urban population of South Asia ( [[#UN-Habitat--2020|UN-Habitat, 2020]] ). Informality is particularly important in understanding climate risks and responses in cities and settlements, and also in relation to key infrastructure ( [[#Trundle--2020|Trundle, 2020]] ; Taylor et al., 2021).

Evidence since AR5 confirms that occupants of informal settlements are particularly exposed to climate events given low-quality housing, limited capacity to adapt, and limited or no risk-reducing infrastructure ( ''high confidence'' ) ( [[#Melore--2020|Melore and Nel, 2020]] ; Twinomuhangi et al., 2021; Satterthwaite et al., 2020; Patel et al., 2020a)(see [[#6.2|Section 6.2]] and case study). The impacts of COVID-19 are also increasingly impacting high-density informal and slum settlements where social distancing and access to water for handwashing are limited (Bhide, 2020; Pinchoff et al., 2021; Tagliacozzo, Pisacane and Kilkey, 2021; [[#Wilkinson--2020|Wilkinson, 2020]] ). This compounds pre-existing vulnerability to climate change associated hazards. Box 6.1 expands on trends in informality as part of global urbanism, peri-urbanisation and suburbanisation, with implications for the global distribution of climate risks and adaptive capacity.

Adaptation and related concepts of urban climate resilience are also concerns for the broader agenda of sustainable development (Wachsmuth, Cohen and Angelo, 2016). Urban areas can play a positive role in advancing sustainability, but the pace and scale of urban development can also undermine progress in SDGs ( [[#Barnett--2016|Barnett and Parnell, 2016]] ; Maes et al., 2019; Anarfi, Hill and Shiel, 2020) ( ''high confidence'' ). With careful planning, urbanisation can be a transformative force, enhancing equity and well-being through co-benefits and synergies between climate change adaptation, equitable urban development and mitigation ( ''medium evidence, medium agreement'' ) ( [[#Parnell--2016a|Parnell, 2016a]] ; Solecki et al., 2015; [[#Sharifi--2020|Sharifi, 2020]] ). Cities can be effective change agents when supported by networked local and national institutions, including professional bodies ( ''high confidence'' ) (Andonova, Hale and Roger, 2017; [[#Brandtner--2021|Brandtner and Suárez, 2021]] ; Heidrich et al., 2016; [[#Kern--2019|Kern, 2019]] ; [[#Farzaneh--2020|Farzaneh and Wang, 2020]] ). Low Emission Development Strategies (LEDS) have developed effective science–policy interactions to support energy-system, environmental and economic development planning strategies in the city of Shanghai, China ( [[#Farzaneh--2020|Farzaneh and Wang, 2020]] ). New literature is emerging about how adaptive changes at the urban level could integrate both far reaching rapid emission reduction and community protection in transformative ways ( [[#Wamsler--2018|Wamsler and Raggers, 2018]] ; [[#Rosenzweig--2018|Rosenzweig and Solecki, 2018]] ; [[#UN-Habitat--2020|UN-Habitat, 2020]] ; [[#Ziervogel--2019a|Ziervogel, 2019a]] ). There is an increasing consensus about the need for integrated governance of urban areas within and across regions, so that urban risk management and adaptation happen hand in hand with more general processes of transition toward more sustainable urban regions ( [[#Simon--2016|Simon, 2016]] ; [[#UN-Habitat--2020|UN-Habitat, 2020]] ).

Since AR5, there has also been increasing recognition of the contribution of diverse knowledges including local and Indigenous knowledge in contributing to the development and interpretation of urban relevant climate change data and policy for effective action (Klenk et al., 2017; Hosen, Nakamura and Hamzah, 2020; [[#Makondo--2018|Makondo and Thomas, 2018]] ). Indigenous and local knowledge inform coping strategies in urban adaptation planning and new directions for action (Nakashima, Krupnik and Rubis, 2018; Abudu Kasei, Dalitso Kalanda-Joshua and Tutu Benefor, 2019). Indigenous and local knowledge is also found to shape perceptions about urban climate risk awareness, its acceptable limits, causation and preferences for adaptation (see also Pyhälä et al., 2016 for a review; see Jaakkola, Juntunen and Näkkäläjärvi, 2018 for impacts on Indigenous peoples in the EU; Saboohi et al., 2019). Local perceptions about climate change in turn influence adaptation behaviours in settlements and urban communities (Lee et al., 2015; Larcom, She and van Gevelt, 2019). Engagement with Indigenous and local knowledge is an enabling condition for planning community-appropriate climate adaptation responses (Fernández-Llamazares et al., 2015). Urban decision making that includes Indigenous and local knowledge has co-benefits for addressing indigenous dispossession, historical inequities and marginalisation of indigenous values that occurred (Parsons et al., 2019; [[#Carter--2019|Carter, 2019]] ; Maldonado et al., 2016; Orlove et al., 2014; Pearce et al., 2015). Indigenous and local knowledge can help deliver culturally appropriate strategies and local choices for urban risk management through, for example community-based observation networks (Alessa et al., 2016), integrating ecosystem-based adaptation strategies in institutional structures (Nalau et al., 2018), using multiple evidence-based approaches (Tengö et al., 2014), and adopting forms of governance that centre Indigenous peoples in urban adaptation and decision making ( [[#Horn--2018|Horn, 2018]] ; Parsons, Fisher and Nalau, 2016).

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'''Box 6.1 | Planetary Urbanisation and Climate Risk'''
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The scale, reach and complexity of contemporary urbanisation compounds climate risks and conditions adaptation ( ''high confidence'' ) ( [[#Miller--2017|Miller and Hutchins, 2017]] ; Rosenzweig et al., 2018b). Urbanisation manifests as a heterogeneous and plural process with varied spatial manifestations ( [[#Oswin--2018|Oswin, 2018]] ) that extends beyond cities and settlements, defining actions elsewhere in what has been called ‘planetary urbanization’ ( [[#Brenner--2014b|Brenner, 2014b]] ). While the concept of planetary urbanisation is contested, for example for a predominantly Eurocentric focus ( [[#Vegliò--2021|Vegliò, 2021]] ), the concept has reflected human urbanisation as a mega-trend of urban expansion and landuse intensification ( [[#Capon--2017|Capon, 2017]] ; [[#Lauermann--2018|Lauermann, 2018]] ). Three dimensions of planetary urbanisation are currently shaping adaptation actions: the new forms and scales of urbanisation, the blurring of boundaries around clearly demarcated territories, and the fragmentation of the urban hinterland into units that serve productive functions for the reproduction of urban space under capitalism ( [[#Brenner--2017|Brenner and Schmid, 2017]] ).

Planetary scale urbanisation challenges current understandings of spatial settlements and how risk affects urban communities ( ''limited evidence, medium agreement'' ) (Ruddick et al., 2018). Massive urbanisation manifests in large agglomerations such as metropolitan areas and urban regions, conurbations with unique risk challenges, particularly when interacting with other drivers of vulnerability ( [[#Adetokunbo--2015|Adetokunbo and Emeka, 2015]] ; Maragno, Pozzer and Musco, 2021). Experiences of regional collaboration to scale adaptation to metropolitan areas have shown to be effective, particularly facilitating information and technology exchanges and institutional cooperation ( [[#Shi--2019|Shi, 2019]] ; [[#Lundqvist--2016|Lundqvist, 2016]] ), but may face challenges such as addressing administrative and fiscal requirements and enrolling local populations in a meaningful participation process ( [[#Shi--2019|Shi, 2019]] ). For example, the coordination of planning policies in the Vienna–Bratislava metropolitan region, further divided by an international border, demonstrates that institutional coordination alone is not sufficient to deliver effective spatial governance: instead, meaningful spatial policies required the involvement of multiple actors ( [[#Patti--2017|Patti, 2017]] ). In addition to institutional coordination, adaptation in rapidly urbanising areas requires understanding how these processes magnify risk and condition urban responses (see also [[#6.3|Section 6.3]] ).

Urban expansion processes affect human settlements everywhere, regardless of their size. Figure 6.1 represents a continuum of settlements from high- to low-density areas ( [[#Ward--2016|Ward and Shackleton, 2016]] ). Urban and rural areas are not always clearly differentiated ( [[#Brenner--2014a|Brenner, 2014a]] ; [[#Brenner--2017|Brenner and Schmid, 2017]] ). For example, in 2010/2011, drought-exacerbated wildfires across Russia’s agricultural hinterland not only led to increased air pollution in Moscow and other large cities in the region, it also disrupted global supply chains of wheat and caused skyrocketing global food prices (Zscheischler et al., 2018). Floods in Bangkok, Thailand in 2011 destroyed many foreign-owned factories, leading to a global shortfall in different types of IT equipment ( [[#Levermann--2014|Levermann, 2014]] ).

Rural areas provide ecosystem services that benefit cities directly, including through reducing hazards (runoff, and temperature) and through carbon storage, and can be maintained through urban markets and other inputs ( [[#Gebre--2019|Gebre and Gebremedhin, 2019]] ). Most urban areas extend into dispersive peri-urban areas where urban and rural land uses co-exist ( [[#Simon--2016|Simon, 2016]] ) and/or suburban areas which are lower density and primarily residential in function. Moreover, the urban and rural differentiation creates normative expectations at the heart of planning conflicts and constraints of urban governance (Taylor, Butt and Amati, 2017). Expanding peri-urban areas pose specific structural constraints to addressing risks. In Bogotá, Colombia, a study found marked inequalities as more impoverished families had restricted access to peri-urban forests, trees and tree services (Escobedo et al., 2015). Factors such as limited land ownership and tenure insecurity in peri-urban areas hinder people’s ability to invest in permanent infrastructure to buffer themselves from flood events, as witnessed in the slums in Nairobi (Thorn, Thornton and Helfgott, 2015). Building resilience and adaptation via community mobilisation may not be effective in peri-urban areas shaped by migration, agricultural intensification and industrialisation ( [[#Wandl--2017|Wandl and Magoni, 2017]] ).

At the same time, actions to improve access to peri-urban services almost always improve resilience ( [[#Simon--2016|Simon, 2016]] ) Evidence from Kampala, Addis Ababa, Dar es Salaam, Douala, Ibadan, Nairobi, Dakar and Accra shows that urban and peri-urban agriculture and forestry can support adaptation (Lwasa et al., 2014). In the metropolitan area of Milan, multi-functional agriculture supports a local, more sustainable food chain ( [[#Magoni--2017|Magoni and Colucci, 2017]] ). Since communities in peri-urban areas are often transitory, efforts toward creating social capital by promoting civic engagement are crucial to facilitate collective action (Narain et al., 2017). For example, adaptation actions can help to build the capacity of the community to engage with service providers (Harris, Chu and Ziervogel, 2018; Ziervogel et al., 2017), as demonstrated in parts of peri-urban Kolkata, India and Khulna, and Bangladesh ( [[#Gomes--2018|Gomes and Hermans, 2018]] ; Gomes, Hermans and Thissen, 2018).

Urbanisation on an immense scale blurs the boundaries that previously defined cities and settlements ( [[#Arboleda--2016a|Arboleda, 2016a]] ; [[#Shaw--2015|Shaw, 2015]] ; [[#Brenner--2014a|Brenner, 2014a]] ; [[#OECD%20and%20European%20Commission--2020|OECD and European Commission, 2020]] ; [[#Schmid--2018|Schmid, 2018]] ; Davidson et al., 2019; [[#Wu--2020|Wu and Keil, 2020]] ). For example, peri-urban areas typically extend over multiple government jurisdictions ( [[#Wandl--2017|Wandl and Magoni, 2017]] ). Adaptation actions can be difficult to plan, coordinate, implement and evaluate in these transboundary contexts (Solecki et al., 2018; [[#Srivastava--2020|Srivastava, 2020]] ; [[#Fünfgeld--2015|Fünfgeld, 2015]] ; [[#Rukmana--2020|Rukmana, 2020]] ; Carter et al., 2018). In Medellín, Colombia, a 46-mile-long green belt is being built to stop urban expansion while also protecting urban forests, providing access to green spaces, and reducing urban heat island effects (Anguelovski et al., 2016). However, large-scale infrastructure projects such as this one require coordination between regional transport authorities and the different municipalities in charge of housing and public services, in addition to consulting communities on their social impact (Chu, Anguelovski and Roberts, 2017). Local and regional authorities have competing mandates, such as a competition for taxpaying residents in peri-urban, commuting zones, and different infrastructure investment logics, political drivers and constituent needs. Smaller discrete infrastructure projects that actively engage local populations may provide better opportunities to build resilience across fragmented spaces ( [[#Santos--2017|Santos, 2017]] ; [[#Kamalipour--2020|Kamalipour and Dovey, 2020]] ).

Suburbanisation follows a gradual movement of citizens from high-density urban centres to the suburbs ( [[#Pieretti--2014|Pieretti, 2014]] ). The development of enclaves for higher-income people that appropriate resources and constrain access to those resources for disadvantaged populations has been recorded in places as distant as Santiago de Chile, People’s Republic of China, India, Indonesia and the Philippines (Calvet and Castán Broto, 2016; Phelps, Miao and Zhang, 2020; Bulkeley, Castán Broto and Edwards, 2014; Buchori et al., 2021; [[#Kleibert--2018|Kleibert, 2018]] ). The appropriation of land and resources in enclaves defends exclusive, privileged communities at the expense of everyone else. Enclaves exacerbate inequalities because those who cannot afford to live in the enclave suffer the fragmentation of public services, restrictions in access to resources, and greater exposure to climate risks ( [[#Hodson--2010|Hodson, 2010]] ; Haase et al., 2017). Moreover, suburbanisation is linked to the privatisation of public spaces and the decline of public infrastructures, collective spaces and green projects ( [[#Long--2019|Long and Rice, 2019]] ; North, Nurse and Barker, 2017). Climate gentrification, whereby vulnerable communities are displaced from urban areas with lower climate risks ( [[#UN-Habitat--2020|UN-Habitat, 2020]] ), reconfigures urban areas, for example, as higher-income populations move away from the city centres, as shown in North American cities that have already suffered climate-related impacts such as Miami, Philadelphia and New Orleans (Keenan, Hill and Gumber, 2018; Shokry, Connolly and Anguelovski, 2020; [[#De%20Koning--2020|De Koning and Filatova, 2020]] ; Aune, Gesch and Smith, 2020).

Urbanisation leads to the spatial fragmentation of the hinterland, divided alongside functional units to serve the demands of the capitalist urban economy ( [[#Brenner--2017|Brenner and Schmid, 2017]] ). Urbanisation is thus linked to new intensities of resource exploitation that threaten vulnerable land and ecosystems, as shown in the Amazon, and that extend across scales ( [[#Arboleda--2016b|Arboleda, 2016b]] ; [[#Wilson--2018|Wilson, 2018]] ). The fragmentation of the hinterland for extractivist purposes depletes ecosystem services and further exacerbates cascading risks ( ''high confidence'' ) ( [[#6.2.6|Section 6.2.6]] ).

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<span id="changes-in-the-global-enabling-environment"></span>
=== 6.1.5 Changes in the Global Enabling Environment ===

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This section reports on changes in global enabling environment; the architecture of international agreements available to inform policy for national governments and others on urbanisation and climate adaptation, since the AR5.

Six new international agreements and initiatives have been achieved, each of which has far-reaching implications for the management of rapid urbanisation and climate change: the Paris Climate Agreement ( [[#United%20Nations--2015b|United Nations, 2015b]] ); the 2030 Agenda for Sustainable Development, including the SDGs ( [[#United%20Nations--2015c|United Nations, 2015c]] ); the Sendai Framework for Disaster Risk Reduction ( [[#UNISDR--2015|UNISDR, 2015]] ); the New Urban Agenda ( [[#United%20Nations--2016a|United Nations, 2016a]] ); Addis Ababa Action Agenda (July 2015); and the World Humanitarian Summit (May 2016). Table 6.2 summarises these.

'''Table 6.2 |''' International policy agreements with implications for urbanisation and climate adaptation

{| class="wikitable"
|-
! Agreement

(date of agreement)

! Scope of agreement

! Relevance for cities, settlements and infrastructure

! Relevance for addressing climate change risk

|-
| Sendai Framework for Disaster Risk Reduction

(March 2015)

| Global agreement for reducing disaster risks in all countries and at all levels.

Highlights urbanisation as a key driver of risk and resilience.

| Identifies rapid urbanisation as a key underlying risk factor for disasters and driver of resilience.

Promotes shift from disaster response to disaster risk management and reduction through cooperation between national and local governments. Limited focus on the role of civil society.

| Highlights the need to respond to systemic risk, including compound and cascading risks and impacts from natural, technological and biological hazards. Includes focus on chronic stressors and sudden shocks through governance, planning, disaster response, post-event recovery.

|-
| Addis Ababa Action Agenda

(July 2015)

| Global agreement arising from the International Conference on Financing for Development ( [[#United%20Nations--2015a|United Nations, 2015a]] ) emphasized the need for adequate financing at all levels of government, especially sub-national and local, to support sustainable development, infrastructure and climate mitigation ( [[#UN-Habitat--2016b|UN-Habitat, 2016b]] ).

| Includes general comments on the importance of local actors and recognises the need for strengthening capacities of municipal and local governments.

Commits to ‘support’ local governments to ‘mobilise revenues as appropriate’.

Offers little on how to get finance to support local governments addressing these commitments.

| Financing a critical element of risk reduction in cities and settlements (see [[#6.4|Section 6.4]] ).

Underlying variability of institutional arrangements inhibits development of universal framework.

|-
| Transforming our world: the 2030 Agenda for Sustainable Development

(September 2015)

| Global agreement adopted by 193 governments that includes the 17 Sustainable Development Goals (SDGs).

| SDG11 speaks explicitly to making cities ‘inclusive, safe, resilient and sustainable’. Extensive reference to universal provision of basic services in other SDGs which will require substantial efforts in cities; equality and governance are also stressed.

Focuses on national goals and national monitoring with insufficient recognition of key roles of local and regional governments and urban civil society in addressing most of the SDGs.

| SDG13 on climate action requires action in cities and settlements.

Integrated approach can address underlying drivers of risk.

|-
| The Paris Agreement

(December 2015)

| Global agreement under UN Framework Convention on Climate Change: signed by 194 and ratified by 189 member states (05/01/21).

| References the role of the local or sub-national levels of government and cities as non-state actors.

| Encourages cities to develop specific agendas for climate action (mitigation and adaptation).

|-
| The World Humanitarian Summit

(May 2016)

| Not an agreement, but a summit of 180 member states generating over 3500 commitments to action and addressing the role of non-state actors in reducing risk of climate change related forced displacement of people.

| Includes five agreed ‘core responsibilities’ with relevance for urban areas, and commitments were made by professional associations, non-governmental organisations and networks of local authorities to address these in towns and cities.

| Climate change likely to shape flows of refugees and migrants who are likely to live in highly exposed areas, particularly in low-income cities. However ‘meagre funding for collaboration, poor data collection and sharing’ ( [[#Acuto--2016|Acuto, 2016]] ) limits commitment effectiveness ( [[#Speckhard--2016|Speckhard, 2016]] ).

|-
| The New Urban Agenda (October 2016)

| Global agenda adopted at UN Conference on Housing and Sustainable Urban Development (Habitat III) envisioned national urban policies and adaptation plans as a central device to inform sub-national governments addressing sustainable development.

| Intended as the global guideline for sustainable urban development for 20 years, seeking to provide coherence with other agreements. Focus on national policy and action. Limited recognition of urban governments or civil society as initiators and drivers of change.

| Clearly frames roles for cities within national and international systems in contributing to sustainability (including low-carbon development) and resilience (including adaptation). Frames the role for cities within national and international systems, including an ongoing assessment of their contribution to sustainability and resilience ( [[#Kaika--2017|Kaika, 2017]] ; Valencia et al., 2019).

|}

Alongside new international agreements are a series of new landmark global stocktake reports: three IPCC special reports including the IPCC 1.5 report ( [[#IPCC--2019a|IPCC, 2019a]] ; [[#IPCC--2019b|IPCC, 2019b]] Hoegh-Guldberg et al., 2018), the UN Environment GEO6 (UN Environment, 2019) and IPBES 2019 ( [[#Brondizio--2019|Brondizio et al., 2019]] ), and UNDRR 2019 ( [[#UNDRR--2019|UNDRR, 2019]] ), each have argued for urgent action on climate mitigation and to invest in inclusive strategies for adaptation if the SDGs are to be met. These findings are comprehensively evidenced and do not need to be revisited here. Our starting point then is to assess the science on how inclusive, sustainable development can be delivered through enhanced adaptation to climate change risks.

As a blueprint for advancing human dignity, the SDGs emphasize the need to consider how to achieve a better and more sustainable future while ‘leaving no one behind.’ In doing so, they highlight an agenda focused on well-being, equality and justice. The objective for SDG11 is defined as: ‘Make cities and human settlements inclusive, safe, resilient and sustainable’ with 10 associated targets including ensuring access for all to adequate, safe and affordable housing and basic services; participatory planning; safeguarding heritage features; reducing disasters, particularly water related disasters and economic impacts on the poor; and promoting resource efficiency, mitigation and adaptation to climate change, resilience to disasters, and develop and implement plans, in line with the Sendai Framework for Disaster Risk Reduction. Similarly, SDG9 aims to build resilient infrastructure, promote inclusive and sustainable industrialisation and foster innovation, with associated targets. The IPCC 1.5 special report emphasized that there are often co-benefits in pursuit of SDGs and adaptation strategies where ‘well-designed mitigation and adaptation responses can support poverty alleviation, food security, healthy ecosystems, equality and other dimensions of sustainable development’ ( [[#IPCC--2018|IPCC, 2018]] FAQ5.1). However there may also be negative trade-offs, for example between pursuit of growth and reducing climate change risk ( [[#International%20Council%20for%20Science--2017|International Council for Science, 2017]] ; [[#IPCC--2018|IPCC, 2018]] Executive Summary; Roy et al., 2018a).

The Paris Agreement also envisioned a significantly more active role for cities and other non-state actors in facilitating policy change (Hale, 2016), including through participation in Nationally Determined Contributions (NDCs), although there is little systematic review of the contributions made by cities to NDCs (Hsu et al., 2020; [[#Bäckstrand--2017|Bäckstrand and Kuyper, 2017]] ). Over two-thirds, 113 out of 164, of initial Intended Nationally Determined Contributions (INDCs), prior to ratification, had referenced urban responses in the context of sustainable development, climate mitigation and adaptation ( [[#UN-Habitat--2016a|UN-Habitat, 2016a]] ). Analysis of those INDCs revealed 58 focused on urban climate adaptation, 17 focused on both adaptation and mitigation, and 4 focused on mitigation ( [[#UN-Habitat--2017|UN-Habitat, 2017]] ). Simultaneously, multiple efforts have emerged to align the actions of nation states with those of other actors, including the UNFCC 2014 Global Climate Action Portal (Hsu, Weinfurter and Xu, 2017). While significant optimism has been gathered around the possibility to intervene at sub-national level, the most difficult challenge has been to establish a coherent view of the overall contribution that cities and settlements are making (Hale, 2016; Chan et al., 2015b). Although meeting the Paris goals will require staying within a ‘carbon budget’, supporting rapidly developing urban areas in the Global South to the same infrastructure level as developed cities may consume significant proportions of that budget ( [[#Bai--2018|Bai et al., 2018]] ).

There is increasing international effort among non-Party stakeholders to the Paris Climate Agreement to collaborate to meet the Paris Climate goals ( [[#Data%20Driven%20Yale%20New%20Climate%20Institute%20PBL--2018|Data Driven Yale New Climate Institute PBL, 2018]] ; Chan et al., 2015a). A review of contributions by non-state actors in 2019 by the EU Covenant of Mayors identified 10427 cities with climate commitments, while the Global Covenant of Mayors included 10543 cities representing a population of 969 million citizens ( [[#Palermo--2020|Palermo et al., 2020]] ; [[#Peduzzi--2020|Peduzzi et al., 2020]] ). International efforts also include the United Nations Framework Convention on Climate Change (UNFCCC) Non-State Actor Zone for Climate Action ( [[#Data%20Driven%20Yale%20New%20Climate%20Institute%20PBL--2018|Data Driven Yale New Climate Institute PBL, 2018]] ). There is also a proliferation of new non-governmental and public-private actors that address both adaptation and mitigation in cities and settlements, including: the C40 Cities Climate Leadership Group, 100 Resilient Cities; the Global Resilient Cities Network, We Mean Business, and We Are Still In ( [[#Ireland--2019|Ireland and Clausen, 2019]] ) and the Global Alliance for Buildings and Construction (Dean et al., 2016). However, there is as yet limited research into the effectiveness of these initiatives in enhancing medium and small city adaptation and limited documentation of climate adaptation actions by non-traditional agents, particularly in the Global South ( [[#Lamb--2019|Lamb et al., 2019]] ).

New urban activists and stakeholders, including youth, and Indigenous and minority communities and NGOs alongside business groups have also been visible in the global urban climate debate, pressing for faster, more far-reaching change ( [[#Frantzeskaki--2016|Frantzeskaki et al., 2016]] ; O’Brien, Selboe and Hayward, 2018; Alves, Campos and Penha-Lopes, 2019; [[#Smith--2018|Smith and Patterson, 2018]] ; [[#Crnogorcevic--2019|Crnogorcevic, 2019]] ; [[#Campos--2016|Campos et al., 2016]] ; [[#Hayward--2021|Hayward, 2021]] ). Emergent urban social movements for climate justice often build on established international networks including local activists such as Shack and Slum Dwellers International, while others are inspired by Indigenous movements and are focused on human rights, indigenous sovereignty and land claims, access to water, intergenerational justice, and gender and youth movements coordinated on social media ( [[#Agyeman--2016|Agyeman et al., 2016]] ; [[#Cohen--2018|Cohen, 2018]] ; [[#Ulloa--2017|Ulloa, 2017]] ; [[#Hayward--2021|Hayward, 2021]] ; [[#Prendergast--2021|Prendergast et al., 2021]] ). The emergence of climate justice movements in urban communities has the potential to reframe policy discussion in cities in ways that also bring inequality and climate justice to the fore ( [[#Sheller--2016|Sheller and Urry, 2016]] ), underscoring growing public calls for more far-reaching, transformative changes toward socially just urban transformations ( [[#Akbulut--2019|Akbulut et al., 2019]] ; [[#Foran--2019|Foran, 2019]] ; Vandepitte, Vandermoere and Hustinx, 2019; [[#Smith--2018|Smith and Patterson, 2018]] ).

This section demonstrates the consistency with which urban processes and places have been rising to the top of international agreements and agendas in the last 10 years ( [[#Bulkeley--2015|Bulkeley, 2015]] ; [[#van%20der%20Heijden--2018|van der Heijden et al., 2018]] ; [[#Knieling--2016|Knieling, 2016]] ). However, many cities, particularly smaller cities and informal settlements in the Global South where development is rapid, need greater support for local governance, more information, and more diverse sources of finance to meet the vision of global climate agreements (Greenwalt, Raasakka and Alverson, 2018; [[#Cohen--2019|Cohen, 2019]] ). Moreover, the response of many cities to climate change is often constrained by wider political, social and economic structures, development path dependences and high carbon lock in ( [[#Princeti--2016|Princeti, 2016]] ; [[#Johnson--2018|Johnson, 2018]] ; [[#Jordan--2015|Jordan et al., 2015]] ).

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<span id="impacts-and-risks"></span>