Climate Change and U.S. Cities: Urban Systems, Sectors, and Prospects for Action

By William D. Solecki and Cynthia Rosenzweig

Approximately 80% of the U.S. population now lives in urban metropolitan areas, and this number is expected to grow significantly in the coming years. At the same time, the built infrastructure sustaining these populations has become increasingly vulnerable to climate change. Stresses to existing systems, such as buildings, energy, transportation, water, and sanitation are growing. If the status quo continues, these systems will be unable to support a high quality of life for urban residents over the next decades, a vulnerability exacerbated by climate change impacts. Understanding this dilemma and identifying a path forward is particularly important as cities are becoming leading agents of climate action.

Prepared as a follow-up to the Fourth National Climate Assessment (NCA), Climate Change and U.S. Cities documents the current understanding of existing and future climate risk for U.S. cities, urban systems, and the residents that depend on them. Beginning with an examination of the existing science since 2012, chapters develop connections between existing and emerging climate risk, adaptation planning, and the role of networks and organizations in facilitating climate action in cities. From studies revealing disaster vulnerability among low-income populations to the development of key indicators for tracking climate change, this is an essential, foundational analysis. Importantly, the assessment puts a critical emphasis on the cross-cutting factors of economics, equity, and governance.

Urban stakeholders and decision makers will come away with a full picture of existing climate risks and a set of conclusions and recommendations for action. Many cities in the United States still have not yet planned for climate change and the costs of inaction are great. With bold analysis, Climate Change and U.S. Cities reveals the need for action and the tools that cities must harness to effect decisive, meaningful change.
 

• Language: English
• Publisher: Island Press
• Release date: Feb 8, 2022
• ISBN: 9781610919791

Book preview

Chapter 1

Introduction: Cities and Climate Change Connections

CONVENING LEAD AUTHORS:

William Solecki (City University of New York),

Cynthia Rosenzweig (NASA GISS)

LEAD AUTHORS:

Radley Horton (Columbia University),

Alex de Sherbinin (Columbia University – CIESIN)

THE GOAL OF THIS BOOK IS TO ASSESS the new knowledge and information about climate change and U.S. cities.¹ It is now known that climate change is already being experienced by U.S. cities through gradual shifts in climate variables and through extreme events (Melillo et al. 2014). This book attempts to document the state-of-the-art understanding of current and future climate risk for U.S. cities, urban systems and the residents that depend on them. Contemporary climate change represents an era of increasing climate variability that is driving urban managers and residents to be more flexible and adaptive in response to these dynamic risks. Urban systems such as water, energy, and transportation infrastructure are designed and managed to operate within an expected range of environmental conditions. Climate change is associated with gradual and punctuated shifts in the environmental baseline of cities and in turn is placing increased stress on city life.

This book is an expansion and extension of the urban focused assessment research presented in the 2014 U.S. National Climate Assessment and a follow-up to the work being done as part of the Fourth National Climate Assessment due to be released at the end of 2018. Urban issues have played an important role in large scale climate assessment activities since the late 1990s. For example, as part of the initial National Climate Assessment in 2000, Rosenzweig and Solecki (2001) led the development of the first major assessment of how a large city and its surrounding metropolitan region could be impacted by climate variability and change. The work focued on the New York Metropolitan Region. For the 2009 Assessment, climate change and cities issues were presented within several sections of the report. The results of 2009 assessment provided some updates of the findings from the 2000 asssesment effort with a focus on new climate models and associated impacts and vulnerabilities. The 2014 National Climate Assessment for this first time includes a chapter with urban in its title (i.e., Chapter 11 – Vulnerability, Urban, and Infrastructure). The NCA4 also will include an urban related chapter.

The research team assembled for this book focused on an assessment of the scholarly literature of climate change and U.S. cities, with an emphasis on research findings generated in the past five years (since early 2012). The scope of the book is to create a foundational document on climate change and U.S. cities that assesses state-of-the-art knowledge and information across a broad set of topics. The assessment is designed to be policy relevant that is particularly important as cities have become agents of climate action moving forward after the COP21 meeting in December of 2015 and the resulting Paris Agreement. The audience for this current assessment book includes a wide variety of interested parties, including policymakers, academics, and science and technical experts, as well as the general public.

1.1 Urban Issues - Results from previous U.S. National Climate Assessments

As part of the 2000 U.S. National Climate Assessment the Climate Change and a Global City Report was published (Rosenzweig and Solecki 2001). The most significant conclusions from that assessment illustrated the key potential impacts, vulnerabilities, opportunities and challenges across a set of set of urban sectors including water, energy, transportation, public health, and decision-making. The assessment documented that climate change already was having an impact on the region and that significant populations and assets were at risk. Because of the tightly coupled character of urban systems, integrative or cascading impacts from extreme climate events could occur in urban areas.

For the 2009 national climate assessment, further advancement was made with respect to understanding climate change in cities. Urban issues were embedded in several sections of the report including in the chapter entitled Society, small sections within two regional chapters (Northeast and Southwest), and occasional references to cities and high-density settlements in other chapters. Differential vulnerability of populations and infrastructure was highlighted in the report. It was stated that urban areas have unique vulnerabilities to climate change, as these areas are already stressed systems, have large at-risk populations and intense concentrations of critical infrastructure, and existing climate risks such as heat islands, and inland and coastal flooding. The 2009 report also provided additional insights into the actions that cities had begun to take to adapt to climate change, particularly with respect to protection of vulnerable infrastructure and populations during extreme climate events such as heat waves and storm surge events. Specific activities noted include heat early warning systems and the procurement of heat resistant materials, and initial discussions regarding the increasing vulnerability of near-shore locations.

For the 2014 National Climate Assessment, several key findings were derived including that U.S. cities are already experiencing the effects of climate change and greater impacts are expected with the onset of an increasingly dynamic climate. This was deemed to be especially important since approximately 245 million residents, or 80% of the U.S. population, now live in urban metropolitan areas, the definition of which includes core cities and extended suburban and exurban areas. This number is expected to grow to 364 million by 2050 (U.S. Census Bureau 2012). The built infrastructure within cities and connected to cities which sustains these populations has become increasingly fragile and deficient and increasingly vulnerable to climate change (Solecki et al. 2013; Wilbanks et al. 2012). Existing built infrastructure systems (such as buildings, energy, transportation, water, and sanitation systems) are expected to become increasingly stressed and, if the status quo continues, unable to support a high quality of life for urban residents over the next decades – especially when the impacts of climate change are added to the equation (McCrea et al. 2011).

The U.S. National Climate Assessment currently incorporates a sustained assessment process in which climate modeling, adaptation and resiliency program evaluation, and implementation of monitoring climate change indicators and metrics have been developed and are in various stages of implementation. These ongoing activities have provided the foundation for the ongoing 4th National Climate Assessment (NCA4).

1.2 Cities and Climate Change – Their Emerging Future Together

As presented by global climate modeling scenarios, future climate change in cities will manifest as directional shifts in average annual climate-related conditions such as higher average annual temperature, more rapid sea level rise as well as an increased frequency and intensity of extreme weather events including extended heat waves and more intense storms. Observed climate data from the early 20th century to the present illustrate a shift in the frequency and magnitude of extreme events, particularly with respect to an increased rate of heavy precipitation events and the occurrence of heat waves. Worst-case scenarios for future climate change include instances where multiple extreme events occur at the same time – for example, a large coastal storm with tidal surge and flooding coincident with an extreme heat event.

Climate change will increase the exposure and vulnerability of cities and their residents to these hazards. Climate-related shifts represent significant challenges as well as potential opportunities for these systems and their managers. Increased climate variability and directional change poses a series of interrelated challenges to the country’s cities. The impact of climate will be compounded by the fact that the U.S. is highly urbanized, with about 80% of its population living in cities and metropolitan areas. The potential impact of climate change is compounded by the fact that many cities depend on critical infrastructure, like water and sewage systems, roads, bridges, and power plants, that are aging and in need of repair or replacement. Rising sea levels, storm surges, heat waves, and extreme weather events will compound these issues, stressing or even overwhelming these essential services.

Cities have become early responders to climate change challenges and opportunities due to two simple facts (Rosenzweig et al. 2010). Urban areas have large and growing populations that are vulnerable for many reasons to climate variability and change. Cities also depend on extensive infrastructure systems and the resources that support them. These systems often extend to, or derive from, rural locations at great distances from urban centers. Urban residents are particularly vulnerable to disruptions in essential infrastructure services, in part because many of these infrastructure systems are reliant and interdependent on each other. For example, electricity is essential to multiple systems, and a failure in the electrical grid can affect water treatment, transportation services, telecommunications, and public health. As climate change impacts increase, climate-related events also will have large consequences for significant numbers of people living in cities or the extended suburbs of metropolitan regions. These changing conditions also create opportunities and challenges for urban climate adaptation, and many cities have begun adopting plans to address these changes.

Events like Hurricane Katrina and Sandy and the more recent Hurricanes Harvey, Irma, and Maria and the fires and flooding in California have alerted the nation’s urban residents to the emergence of a new climate normal that is a result of climate change. In this new normal, unprecedented extreme events can occur and the prospects of gradual environmental shifts, like sea level rise, will exacerbate future environmental stress on urban systems and the daily life of urban residents. A rich literature of specific case studies on these topics have emerged (e.g. Berardy and Chester 2017; Cheng et al. 2017; Hauer 2017) as well as systematic appraisals and frameworks regarding how to manage these risks (e.g., Depietri and McPhearson; Reckien 2017; Solecki et al. 2017; Wallace 2017). Another growing issue, also incorporated into this book, is the recognition that climate change is not isolated from existing risks, challenges, and opportunities present within the structure and functioning of cities. These elements are directly linked and in this context, climate change will potentially make existing urban climate risks worse and result in impediments to economic development (see as example Dinan 2017; Gornitz et al. 2017; and Petkova 2017). This book attempts to capture the key findings and new information that emerges from this collective yet diverse literature and in turn provide a benchmark of new knowledge.

1.3 Scientific Background

This book takes an explicitly systems-level perspective to detail and understand the connections between climate change and cities. The book focuses on how the climate shifts influence changes in urban systems such as water and energy supply, transportation and public health, and what societal context conditions like economics, governance, legal regimes and insurance mediate and influence these connections.

To understand and illustrate the connections between climate change and cities at the sector and service level, the study focuses on how climate change will shift the function, structure, or organization of specific sectors or services and thereby reveal system-level challenges for adaptation strategies, vulnerabilities and opportunities. How these impacts, vulnerabilities, and adaptation strategies are mediated by a set of cross-cutting factors such as economics, equity, and governance is another critical component of the assessment process.

1.4 Guiding Framework

The assessment utilizes several conceptual outlines to structure its analytical discussion of climate change and cities. The assessment utilizes an urban climate risk conceptual framework for examining climate risk, climate scenarios, and the urbanization process. The urban climate risk framework utilized here incorporates several basic elements including existing and emerging climate risk, interactions with urban sectors and services which help illustrate a set of vulnerabilities, impacts, and adaptation strategies which in turn are mediated by a set of cross-cutting issues and urbanization context. The diagram below illustrates of some these basic relationships.

Figure 1-1 shows a simple conceptual framework that illustrates how current and emerging climate risks are translated through urban sectors and services thereby fostering the development of a variety of vulnerabilities, impacts, and adaptation challenges and opportunities. This process is deeply connected to and influenced by ongoing urbanization processes in individual cities and extended metropolitan regions. The urbanization processes connect the climate risk, urban systems and vulnerabilities, impacts, and adaptation through a set of cross-cutting issues such as governance capacity and resources including the level of local expertise and budget structure.

This assessment recognizes that there are several existing climate hazards present in U.S. cities. Key hazards include sea level rise and coastal storm surge, heat waves, intense precipitation and riverine and street level flooding, drought, extreme wind events, urban heat islands, secondary air pollutants, and cold air events including frozen precipitation. Current key climate risks, which include conditions of likelihood and consequence faced by U.S. cities, include the following:

Image: Figure 1-1. Urbanization Risk Assessment Framework. Source: authors.

Figure 1-1. Urbanization Risk Assessment Framework. Source: authors.

• Populations vulnerable to river and coastal flooding;

• Major population centers on the nation’s coasts have assets and populations exposed to flooding and associated equity issues;

• Economic loss potential much greater than insured loss; significant non-market value losses also a risk; and,

• Major coastal storm events (e.g., hurricane) could result in ~ hundreds of billions of dollars of economic losses.

• Public health crises and economic losses resulting from a large scale extreme heat event.

Climate change in most cases will exacerbate these risks, with exception of the frequency of extreme cold events which will likely decrease over time. The nation will experience more days of extreme heat events particularly in the southern half of the U.S., as well as more days of extreme precipitation particularly in the Northeast and Midwest. As highlighted in Chapter 2, many areas of the country also have experienced significant relative and absolute population growth in the most recent decade and are expected to have more growth in the future. It is in this dynamic context – accelerating climate change and rapid urbanization – where the conditions of climate change could be most challenging, such as the urbanizing areas of the southeast, intermountain west and arid southwest, especially southern California and Arizona.

1.4.1 Climate Change and Dynamic Urbanization

The process of climate change overlays a dynamic pattern of urbanization in the United States. The country’s population continues to become more metropolitan focused as opposed to rural while the increase in per capita rate of land conversion drives ever more land use shifts from agricultural and rural land to urban, suburban and extended exurban land. Urban growth surged in the early 1990s but slowed slightly even as the number living in cities including core cities and suburban areas continued to grow. Currently approximately 80 percent of the U.S. population lives in extended metropolitan regions. The spatial extent and population of urban areas continue to grow. As a percentage of growth, most of the nation’s recent growth took place in the metropolitan areas of the American South and intermountain west and west coast.

As a group, cities in the U.S. are defined by a broad variety of densities, locations, and physical and social contexts ranging from older high density urban cores such as Manhattan, the Loop area of Chicago and parts of San Francisco to much lower density (often by a factor 15 to 20 times) newer, extended suburban and exurban locations around Las Vegas, Dallas, and Orlando. More than half of the total U.S. population now lives in suburban settings. The inherent variety of urban settings influences the relative impact of climate change and the vulnerability and adaptive capacity of urban systems.

1.5 Key Definitions

Several key definitions are used to frame the book and assessment process. These include the following including several for which the definition is derived from the IPCC AR4 (2014) and the U.S. National Climate Assessment (2014) Glossary materials.

• Adaptation – Initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects. Various types of adaptation exist (e.g. anticipatory and reactive, private and public, and autonomous and planned). Examples are raising river or coastal dikes, the substitution of more temperature-shock resistant plants for sensitive ones, etc.

• Climate Change – Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.

• Climate Impacts – Shifts that result from climate change including positive or negative impacts as measured by social, ecological and economic metrics. Impacts can be abrupt and sudden, or emerge slowly over time; easy or difficult to discern; appear in the near future or distant future with continued and/or accelerated climate change.

• Risk – A metric to illustrate the relative severity of a hazard; also can be defined as probability times the event consequence.

• Urban – Settlement patterns which are high to medium population density with interconnected infrastructure systems and commuting patterns and a high concentration of cultural, economic, and political institutions.

• Urban System – An integrated set of components and processes which define the flows and storage of materials and energy in an urban context, which include feedback mechanisms and other regulatory controls and boundary conditions. Examples include urban water supply systems and energy supply systems, which involve coupled natural and human components.

• Urbanization – The conversion of land from a natural state or managed natural state (such as agriculture) to cities; a process driven by net rural-to-urban migration through which an increasing percentage of the population in any nation or region come to live in settlements that are defined as urban centers, as well as the rebuilding of existing urban areas through processes of dis(investment) and migration.

• Vulnerability – Vulnerability is the degree to which a system is susceptible to, and unable to cope with the adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity.

1.6 Book Outline Introduction

In addition to this Chapter 1 Introduction, the book is divided into the following chapters: 2. Climate change and urban systems; 3. Urban sectors and services; 4. Critical dimensions of adaptation planning; 5. Sustained urban climate assessment, and 6. Conclusions – Summary and Recommendations

Chapter 2 examines the science underpinnings of the assessment, including an examination of the updated science of climate change and its implications for urban climate risks, and an evaluation of the connection between urban systems and climate risk and dynamic urbanization processes found in U.S. cities and their extended metropolitan regions. The next chapter – Chapter 3 – focuses specifically on the connections between existing and emerging climate risks on urban systems defined as urban sectors and services. These connections include water and wastewater, transportation, energy supply, and public health among others. The focus is on the impacts and vulnerabilities these sectors and services face from climate change risks. Chapter 4 examines the broad suite of adaptation opportunities and challenges now emerging in the U.S. A specific focus is on adaptation planning, adaptation actions and financial and institutional constraints. The following chapter, Chapter 5, examines the role of urban climate networks and organization in facilitating climate action in cities. The final chapter, Chapter 6, provides a set of conclusions and recommendations relevant for urban stakeholders and decision makers.

References

Berardy, A., & Chester, M. V. (2017). Climate change vulnerability in the food, energy, and water nexus: concerns for agricultural production in Arizona and its urban export supply. Environmental Research Letters, 12(3), 035004.

Cheng, C., Yang, Y. E., Ryan, R., Yu, Q., & Brabec, E. (2017). Assessing climate change-induced flooding mitigation for adaptation in Boston’s Charles River watershed, USA. Landscape and Urban Planning, 167, 25-36.

Depietri, Y., & McPhearson, T. (2017). Integrating the Grey, Green, and Blue in Cities: Nature-Based Solutions for Climate Change Adaptation and Risk Reduction. In Nature-Based Solutions to Climate Change Adaptation in Urban Areas (pp. 91-109). Springer, Cham.

Dinan, T. (2017). Projected Increases in Hurricane Damage in the United States: The Role of Climate Change and Coastal Development. Ecological Economics, 138, 186-198.

Gornitz, V., Horton, R., Bader, D. A., Orton, P., & Rosenzweig, C. (2017). Coping with Higher Sea Levels and Increased Coastal Flooding in New York City. In Climate Change Adaptation in North America (pp. 209-223). Springer International Publishing.

Hauer, M. E. (2017). Migration induced by sea-level rise could reshape the US population landscape. Nature Climate Change.

Karl, T. R., J. T. Melillo, and T. C. Peterson. 2009. Global Climate Change Impacts in the United States. edited by T.R. Karl, J.T. Melillo and T.C. Peterson.

McCrea, Rod, Robert Stimson, and Robert W. Marans. 2011. The Evolution of Integrative Approaches to the Analysis of Quality of Urban Life. In Investigating Quality of Urban Life: Theory, Methods, and Empirical Research, edited by W. Robert Marans and J. Robert Stimson, 77-104. Dordrecht: Springer Netherlands.

Melillo, Jerry M, TC Richmond, and Gary W Yohe. 2014. Climate change impacts in the United States: the third national climate assessment. US Global Change Research Program.

Petkova, E. P., Vink, J. K., Horton, R. M., Gasparrini, A., Bader, D. A., Francis, J. D., & Kinney, P. L. (2017). Towards More Comprehensive Projections of Urban Heat-Related Mortality: Estimates for New York City under Multiple Population, Adaptation, and Climate Scenarios. Environmental Health Perspectives, 125(1), 47–55. http://doi.org.ezproxy.gc.cuny.edu/10.1289/EHP166

Reckien, D. (2017). Recent Harm, Problematic Impacts, and Socially Feasible Adaptation Options to Heatwaves and Heavy Rain Events in New York City. In Climate Change Adaptation in North America (pp. 89-102). Springer International Publishing.

Rosenzweig, C. and Solecki, W.D. Eds. 2001. Climate Change in a Global City: The Impacts of Potential Climate Variability and Change in the New York Metropolitan Region. New York: Columbia Earth Institute. 241p.

Rosenzweig, C., W. Solecki, S.A. Hammer, and S. Mehrotra. 2010. Cities lead the way in climate-change action. Nature no. 467 (7318):909-911.

Solecki, W., C. Rosenzweig, S. Hammer, and S. Mehrotra. 2013. The urban transformation: health, shelter and climate change. In The urban transformation: health, shelter and climate change, edited by E. Sclar, N. Volavka-Close and P. Brown, 197-220. Routledge.

US Census Bureau. 2012. 2010 Census Urban and Rural Classification and Urban Area Criteria. https://www.census.gov/geo/reference/ua/urban-rural-2010.html

Wallace, B. (2017). A framework for adapting to climate change risk in coastal cities. Environmental Hazards, 16(2), 149-164.

Wilbanks, T., S.J. Fernandez, G.Backus, P. Garcia, K. Jonietz, P. Kirshen, M. Savonis, B. Solecki, L. Toole, M.R. Allen, R. Bierbaum, T. Brown, N. Brune, J. Buzier, J. Fu, O. Omitaomu, L. Scarlett, M. Susman, E. Vugrin, R. Zimmerman (2012). Climate Change and Infrastructure, Urban Systems and Vulnerabilities: Technical Report to the U.S. Department of Energy in Support of the National Climate Assessment. Island Press.

Notes

1. This report was developed in a multi-step process including a two-day scoping workshop held on the Columbia University campus in October 2011 of approximately 70 cities and climate change experts including representatives from academic, federal and municipal government, and nongovernmental organizations. An earlier version of this assessment was developed in the spring of 2012 to contribute to the U.S. National Assessment effort as technical support document and focused on those relevant materials that had been produced since the most recent major national assessment in 2009 (see Karl et al. 2009). Subsequent to its utilization as background material for Chapter 11 of the National Climate Assessment (eventually released in April 2014) the report has been extensively updated to include material that has become available since the summer of 2012. Each of the chapters has been subject to multiple rounds of internal and external peer review. As of October 2017, the report represents the most extensive report of U.S. climate change and cities.

Chapter 2

Urban Systems and Climate Change in Context

CONVENING LEAD AUTHORS:

Nancy B. Grimm (Arizona State University), Dale Quattrochi

(NASA), Christopher Clark (U.S. Environmental Protection Agency)

LEAD AUTHORS:

Christopher Boone (Arizona State University), Cynthia Rosenzweig

NASA/GISS, Stephanie Pincetl (University of California,