Urban Areas
Coordinating Lead Authors:
Aromar Revi (India), David E. Satterthwaite (UK)
Lead Authors:
Fernando Aragón-Durand (Mexico), Jan Corfee-Morlot (USA/OECD), Robert B.R. Kiunsi
(United Republic of Tanzania), Mark Pelling (UK), Debra C. Roberts (South Africa),
William Solecki (USA)
Contributing Authors:
Jo da Silva (UK), David Dodman (Jamaica), Andrew Maskrey (UK), Sumetee Pahwa Gajjar
(India), Raf Tuts (Belgium)
Review Editors:
John Balbus (USA), Omar-Dario Cardona (Colombia)
Volunteer Chapter Scientist:
Alice Sverdlik (USA)
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Figure 8-1 | Global and regional maps showing the location of urban agglomerations with 750,000-plus inhabitants in 1950 (derived from statistics in UN DESA Population Division, 2012)
This chapter should be cited as:
Revi, A., D.E. Satterthwaite, F. Aragón-Durand, J. Corfee-Morlot, R.B.R. Kiunsi, M. Pelling, D.C. Roberts, and W. Solecki, 2014: Urban areas. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of theIntergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea,T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken,P.R. Mastrandrea, and L.L.White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and NewYork, NY, USA, pp. 535-612.
Table of Contents
Executive Summary................................................................... 538
8.1. Introduction ........................................................................ 541
8.1.1. Key Issues ....................................................................... 541
8.1.2. Scope of the Chapter ....................................................... 541
8.1.3. Context: An Urbanizing World ....................................... 541
8.1.4. Vulnerability and Resilience ........................................... 547
8.1.4.1.Differentials in Risk and Vulnerability within and between Urban Centers ...... 547
8.1.4.2.Understanding Resilience for Urban Centers in Relation to Climate Change .... 548
8.1.5. Conclusions from the Fourth Assessment Report (AR4) and New Issues Raised by this Chapter ................. 5498.2. Urbanization Processes, Climate Change Risks, and Impacts ........ 550
8.2.1. Introduction ................................................................................. 550
8.2.2. Urbanization: Conditions, Processes, and Systems within Cities ...... 551
8.2.2.1.Magnitude and Connections to Climate Change .............................. 551
8.2.2.2. Spatial and Temporal Dimensions ................................................... 551
8.2.2.3.Urbanization and Ecological Sustainability ...................................... 552
8.2.2.4.Regional Differences and Context-Specific Risks ............................ 552
8.2.3. Climate Change and Variability: Primary (Direct) and Secondary (Indirect) Impacts .. 552
8.2.3.1.Urban Temperature Variation: Means and Extremes ......................... 552
8.2.3.2.Drought and Water Scarcity: Means and Extremes ............................ 555
8.2.3.3.Coastal Flooding, Sea Level Rise, and Storm Surge .......................... 555
8.2.3.4.Inland Flooding and Hydrological and Geo-Hydrological Hazards at Urban Scale .... 555
8.2.3.5. Emerging Human Health, Disease, and Epidemiology Issues in Citie.............. 556
8.2.4. Urban Sectors: Exposure and Sensitivity ..................................... 556
8.2.4.1.Water Supply,Wastewater, and Sanitation ................................. 557
8.2.4.2. Energy Supply ........................................................................... 558
8.2.4.3. Transportation and Telecommunications .................................. 558
8.2.4.4.Built Environment, and Recreation and Heritage Sites .............. 559
8.2.4.5.Green Infrastructure and Ecosystem Services ............................ 560
8.2.4.6.Health and Social Services .......................................................... 560
8.2.5. Urban Transition to Resilience and Sustainability ........................ 560
8.3. Adapting Urban Areas ...................................................................... 563
8.3.1. Introduction .................................................................................... 563
8.3.2. Development Plans and Pathway.................................................... 563
8.3.2.1.Adaptation and Development Planning ................................. 564
Box 8-1. Recent Literature on Urban Adaptation in Low- and Middle-Income Nations ... 564
8.3.2.2.Disaster Risk Reduction and Its Contribution to Climate Change Adaptation ....... 565
8.3.3. Adapting Key Sectors ................................................................ 566
8.3.3.1.Adapting the Economic Base of Urban Centers ....................... 566
8.3.3.2.Adapting Food and Biomass for Urban Populations ............... 568
8.3.3.3.Adapting Housing and Urban Settlements ............................... 568
8.3.3.4.Adapting Urban Water, Storm, and Waste Systems ................. 570
8.3.3.5.Adapting Electric Power and Energy Systems .......................... 571
8.3.3.6.Adapting Transport and Telecommunications Systems ............ 571
8.3.3.7.Green Infrastructure and Ecosystem Services within Urban Adaptation .... 572
Box 8-2. Ecosystem-Based Adaptation in Durban .................................. 573
8.3.3.8.Adapting Public Services and Other Public Responses ............... 575
8.4. Putting Urban Adaptation in Place: Governance, Planning, and Management .. 575
8.4.1. Urban Governance and Enabling Frameworks, Conditions, and Tools for Learning .. 576
8.4.1.1.Multi-Level Governance and the Unique Role of Urban Governments ........ 576
8.4.1.2.Mainstreaming Adaptation into Municipal Planning ..................................... 578
8.4.1.3.Delivering Co-Benefits ................................................................ 578
8.4.1.4.Urban Vulnerability and Risk Assessment Practices: Understanding Science, Development, and Policy Interactions ............ 579
8.4.1.5.Assessment Tools: Risk Screening, Vulnerability Mapping, and Urban Integrated Assessment .......................... 579
8.4.2. Engaging Citizens, Civil Society, the Private Sector, and Other Actors and Partners ... 580
8.4.2.1. Engaging Stakeholders in Urban Planning and Building Decision Processes for Learning ......................... 580
8.4.2.2. Supporting Household and Community-Based Adaptation ......... 580
8.4.2.3.Private Sector Engagement and the Insurance Sector ................... 582
Box 8-3. Micro-Finance for Urban Adaptation ......................................... 584
8.4.2.4.Philanthropic Engagement and Other Civil Society Partnerships .. 584
8.4.2.5.University Partnerships and Research Initiatives ............... 585
8.4.2.6.City Networks and Urban Adaptation Learning Partnerships ........ 585
8.4.3. Resources for Urban Adaptation and Their Management ................ 585
8.4.3.1.Domestic Financing: Tapping into National or Subnational Regional Sources of Funding and Support ........................... 586
Box 8-4. Environmental Indicators in Allocating Tax Shares to Local Governments in Brazil ....................................... 587
8.4.3.2.Multilateral Humanitarian and Disaster Management Assistance ........................................................................................ 587
8.4.3.3.International Financing and Donor Assistance for Urban Adaptation .......... 588
8.4.3.4.Institutional Capacity and Leadership, Staffing, and Skill Development ...... 589
Box 8-5. Adaptation Monitoring: Experience from New York City ......................... 589
8.4.3.5.Monitoring and Evaluation to Assess Progress ............................................. 590
8.5. Annex: Climate Risks for Dar es Salaam, Durban, London, and New York City ... 590
References .......................................................................................................... 590
Frequently Asked Questions
8.1: Do experiences with disaster risk reduction in urban areas provide useful lessons for climate-change adaptation? ........................ 565
8.2: As cities develop economically, do they become better adapted to climate change? .... 567
8.3: Does climate change cause urban problems by driving migration from rural to urban areas? ..................... 568
8.4: Shouldn’t urban adaptation plans wait until there is more certainty about local climate change impacts? ..................................... 580
Executive Summary
Urban climate adaptation can build resilience and enable sustainable development. {8.1, 8.2, 8.3}
Action in urban centers is essential to successful global climate change adaptation. Urban areas hold more than half the world’s population and most of its built assets and economic activities. They also house a high proportion of the population and economic activities most at risk from climate change, and a high proportion of global greenhouse gas emissions are generated by urban-based activities and residents (medium confidence, based on medium evidence, high agreement). {8.1}
Much of key and emerging global climate risks are concentrated in urban areas. Rapid urbanization and rapid growth of large cities in low- and middle-income countries have been accompanied by the rapid growth of highly vulnerable urban communities living in informal settlements, many of which are on land at high risk from extreme weather (medium confidence, based on medium evidence, high agreement). {8.2, 8.3, Tables 8-2, 8-3}
Cities are composed of complex inter-dependent systems that can be leveraged to support climate change adaptation via effective city governments supported by cooperative multilevel governance. This can enable synergies with infrastructure investment and maintenance, land use management, livelihood creation, and ecosystem services protection (medium confidence, based on limited evidence, medium agreement). {8.3, 8.4}
Urban adaptation action that delivers mitigation co-benefits is a powerful, resource-efficient means to address climate change and to realize sustainable development goals (medium confidence, based on medium evidence, high agreement). {8.4}
Urban climate change risks, vulnerabilities, and impacts are increasing across the world in urban centers of all sizes, economic conditions, and site characteristics. {8.2}
Urban climate change-related risks are increasing (including rising sea levels and storm surges, heat stress, extreme precipitation, inland and coastal flooding, landslides, drought, increased aridity, water scarcity, and air pollution) with widespread negative impacts on people (and their health, livelihoods, and assets) and on local and national economies and ecosystems (very high confidence, based on robust evidence, high agreement). These risks are amplified for those who live in informal settlements and in hazardous areas and either lack essential infrastructure and services or where there is inadequate provision for adaptation. {8.2, Table 8-2}
Climate change will have profound impacts on a broad spectrum of infrastructure systems (water and energy supply, sanitation and drainage, transport and telecommunication), services (including health care and emergency services), the built environment, and ecosystem services. These interact with other social, economic, and environmental stressors exacerbating and compounding risks to individual and household well-being (medium confidence, based on medium evidence, high agreement). {8.2}
Cities and city regions are sufficiently dense and of a spatial scale that they influence their local micro-climate. Climate change will interact with these conditions in a variety of ways, some of which will exacerbate the level of climate risk (high confidence, based on robust evidence, high agreement). {8.2}
Urban climate adaptation provides opportunities for both incremental and transformative development. {8.3, 8.4}
Urban adaptation provides opportunities for incremental and transformative adjustments to development trajectories toward resilience and sustainable development via effective multilevel urban risk governance, alignment of policies and incentives, strengthened local government and community adaptation capacity, synergies with the private sector, and appropriate financing and institutional development. Opportunities to do so are high in many rapidly growing cities where institutions and infrastructure are being developed, though there is limited evidence of this being realized in practice (medium confidence, based on limited evidence, high agreement). {8.4}
Urban adaptation can enhance economic comparative advantage, reducing risks to enterprises and to households and communities (medium confidence, based on medium evidence, high agreement). {8.3}
City-based disaster risk management with a central focus on risk reduction is a strong foundation on which to address increasing exposure and vulnerability and thus to build adaptation. Closer integration of disaster risk management and climate change adaptation along with the incorporation of both into local, subnational, national, and international development policies can provide benefits at all scales (high confidence, based on medium evidence, high agreement). {8.3}
Ecosystem-based adaptation is a key contributor to urban resilience (medium confidence, based on medium evidence, high agreement (among practitioners)). {8. 3}
Effective urban food-security related adaptation measures (especially social safety nets but also including urban and peri-urban agriculture, local markets, and green roofs) can reduce climate vulnerability especially for low-income urban dwellers (medium confidence, based on medium evidence, medium agreement). {8.3}
Good quality, affordable, well-located housing provides a strong base for city-wide climate change adaptation minimizing current exposure and loss. Possibilities for building stock adaptation rest with owners and public, private, and civil society organizations (high confidence, based on robust evidence, high agreement). {8.3, 8.4}
Reducing basic service deficits and building resilient infrastructure systems (water supply, sanitation, storm and waste water drains, electricity, transport and telecommunications, health care, education, and emergency response) can significantly reduce hazard exposure and vulnerability to climate change, especially for those who are most at risk or vulnerable (very high confidence, based on robust evidence, high agreement). {8.3}
For most key climate change associated hazards in urban areas, risk levels increase from the present (with current adaptation) to the near term but high adaptation can reduce these risk levels significantly. It is less able to do so for the longer term, especially under a global mean temperature increase of 4°C. {Tables 8-3, 8-6}
Implementing effective urban adaptation is possible and can be accelerated. {8.4}
Urban governments are at the heart of successful urban climate adaptation because so much adaptation depends on local assessments and integrating adaptation into local investments, policies, and regulatory frameworks (high confidence). {8.4} Well governed cities with universal provision of infrastructure and services have a strong base for building climate resilience if processes of planning, design, and allocation of human capital and material resources are responsive to emerging climate risks (medium confidence, based on medium evidence, high agreement). {8.4}
Building human and institutional capacity for adaptation in local governments, including scope for reflecting on incremental and transformative adaptation pathways, accelerates implementation and improves urban adaptation outcomes (high confidence, based on medium evidence, high agreement). {8.4}
Coordinated support from higher levels of governments, the private sector, and civil society and horizontal learning through networks of cities and practitioners benefits urban adaptation (medium confidence, based on medium evidence, medium agreement). {8.4}
Leadership within local governments and also across all scales is important in driving successful adaptation and in promoting and sustaining a broad base of support for the urban adaptation agenda (medium confidence, based on medium evidence, high agreement). {8.4}
Addressing political interests, mobilizing institutional support for climate adaptation, and ensuring voice and influence to those most at risk are important strategic adaptation concerns (medium confidence, based on limited evidence, medium agreement). {8.4}
Enabling the capacity of low-income groups and vulnerable communities, and their partnership with local governments, can be an effective urban adaptation strategy (medium confidence, based on limited evidence, high agreement). {8.3, 8.4}
Urban centers around the world face severe constraints to raising and allocating resources to implement adaptation. In most lowand middle-income country cities, infrastructure backlogs, lack of appropriate mandates, and lack of financial and human resources severely constrain adaptation action. Small urban centers often lack economies of scale for adaptation investments and local capacity to act, as they have relatively low national and international profiles (medium confidence, based on medium evidence, high agreement). {8.3, 8.4}
International financial institutions provide limited financial support for adaptation in urban areas. There is limited current commitment to finance urban adaptation from different levels of government and international agencies (medium confidence, based on limited evidence, high agreement). {8.4}
A scientific evidence base in each urban center is essential for effective adaptation action. This includes local risk and vulnerability assessments and information and data with which to consider current and future risk and adaptation and development options (medium confidence, based on medium evidence, high agreement). {8.4}
Dealing with the uncertainty associated with climate change projections and balancing them with actions to address current vulnerabilities and adaptation costs helps to assist implementation in urban areas (medium confidence, based on medium evidence, medium agreement). {8.2, 8.4}
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