Rapid urbanization is quickly transitioning communities from native vegetation to an engineered infrastructure that reduces evapotranspiration and increases thermal-storage capacity. Technological responses in the urban environment generate additional heat by way of air conditioning, automobiles, and machinery. In addition to anthropogenic heat, the urban geometry of engineered materials has changed net radiation and altered convection, due to slowing winds near buildings [7]. These engineered changes in the characteristics of the land surface and supporting urban systems in turn impact the partitioning of energy at the surface [4]. This is often manifested in microscale and mesoscale modifications to the thermal properties of the surface and atmosphere, and can result in significant increases and rapid change in the urban climate compared to adjacent rural regions, known as the Urban Heat Island Effect (UHI) [5, 86].
The role of engineered materials and their contribution to urban climatology is understood in theory, but in practice the UHI phenomenon is complicated by rapid changes in built-form and spatiotemporal variations in social, economic, and environmental conditions [4]. The very concept of complexity originally arose in concert with atmospheric processes [6], and the systems are made further complex by the increasing role engineered material and engineering designs contribute to regional and global climate, energy and water consumption, air quality, ecological systems, human health, the economy, and the way each of these systems feeds back on each other. We lack sufficient information to assess the risks of the cascading use of engineered materials in the urban setting. The lack of knowledge has lead to either an absence of regulatory frameworks or policies that ignore the emerging understandings of the material-climate-environment system. An integrated analysis of materials use and properties and the feedback relationships with ecological, economic, and social dynamics is necessary to reduce negative impacts of the UHI on human health, quality of life, and ecological integrity.
Rapid change defies simple measures or models. As cities expand in population and built-form on their peripheries or turn over neighborhoods, buildings, and infrastructure in the core, it is a challenging task to measure that change, let alone to model it. The process of urbanization, both as a driver and outcome of change, is highly complex. Even with most sophisticated models, demographers, economists, and land use change modelers have difficulty predicting change accurately. This is especially the case in heterogeneous environments, which cities inherently are. Complexity of urban areas is amplified in rapidly changing metropolises, such as Beijing and Phoenix. Incorporating ecological and engineering dynamics (outcomes and drivers) complicates the models further still. When the very different histories, economies, and systems of governance of China and the United States are added, the models become more inclusive but increasingly complex. Yet, any efforts to mitigate negative impacts to ecology and society, or amplify positive outcomes, requires a systematic analysis of such biocomplexity. In short, any efforts to build, design, or plan sustainable cities requires an acceptance of the complexity of the systems and a willingness to analyze them within a biocomplexity framework. Given the immense amount of energy, materials, and wastes that cities produce and consume, it is urban areas that such analyses are needed most. Global sustainability necessitates particular attention to urban sustainability.
In the US alone, rapid urbanization will result in an expansion of the built environment to 427 billion ft2 by 2030, an increase of more than 40% since 2000. Collectively, the materials/building sector accounts for over 20% of the US economy and the activities associated with constructing and using pavements, infrastructure, and buildings consume 65% of electricity, 37% of primary energy, 25% of water supplies, and 30% of all wood and materials. The built environment and its occupants will generate 35% of solid waste, 36% of CO2 and 46% of SO2 emissions, 19% of NOx and 10% of fine-particulate emissions.
The National Center of Excellence in partnership with the National Center for Environmental Health and the Centers for Disease Control and Prevention (CDC) propose to undertake a research project on Climate Change and the Built Environment. The goal of which is to develop a new research methodology that provides local and regional governments a new set of skills and tools in prevention and emergency response planning for acute and chronic urban climate impacts.
Rising temperatures and the increasing frequency of extreme heat events in cities are major public health threats, but there is little research on the interplay of the built environment (urban morphology) in cities that amplify or attenuate heat-related hazards. The proposed interdisciplinary project will explain how the processes of urbanization differentially distribute vulnerability to extreme heat within cities. Through activities that integrate civil engineering, public health, and climate science, this project will determine how systems respond at multiple scales to the cumulative effects of urban climate change over time. This presentation will present findings that:
1. explain the spatial and temporal character of the Urban Heat Island (UHI) as an emergent phenomenon of interacting processes that involve material selection, changing landscapes, and urban morphology;
2. assess the vulnerability of different communities in representative microclimate conditions to chronic and episodic heat-related health hazards;
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