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

=== 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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