Showing papers on "Urban climate published in 2015"

Mapping local climate zones for a worldwide database of the form and function of cities

Abstract: Progress in urban climate science is severely restricted by the lack of useful information that describes aspects of the form and function of cities at a detailed spatial resolution. To overcome this shortcoming we are initiating an international effort to develop the World Urban Database and Access Portal Tools (WUDAPT) to gather and disseminate this information in a consistent manner for urban areas worldwide. The first step in developing WUDAPT is a description of cities based on the Local Climate Zone (LCZ) scheme, which classifies natural and urban landscapes into categories based on climate-relevant surface properties. This methodology provides a culturally-neutral framework for collecting information about the internal physical structure of cities. Moreover, studies have shown that remote sensing data can be used for supervised LCZ mapping. Mapping of LCZs is complicated because similar LCZs in different regions have dissimilar spectral properties due to differences in vegetation, building materials and other variations in cultural and physical environmental factors. The WUDAPT protocol developed here provides an easy to understand workflow; uses freely available data and software; and can be applied by someone without specialist knowledge in spatial analysis or urban climate science. The paper also provides an example use of the WUDAPT project results.

Global typology of urban energy use and potentials for an urbanization mitigation wedge

Abstract: The aggregate potential for urban mitigation of global climate change is insufficiently understood. Our analysis, using a dataset of 274 cities representing all city sizes and regions worldwide, demonstrates that economic activity, transport costs, geographic factors, and urban form explain 37% of urban direct energy use and 88% of urban transport energy use. If current trends in urban expansion continue, urban energy use will increase more than threefold, from 240 EJ in 2005 to 730 EJ in 2050. Our model shows that urban planning and transport policies can limit the future increase in urban energy use to 540 EJ in 2050 and contribute to mitigating climate change. However, effective policies for reducing urban greenhouse gas emissions differ with city type. The results show that, for affluent and mature cities, higher gasoline prices combined with compact urban form can result in savings in both residential and transport energy use. In contrast, for developing-country cities with emerging or nascent infrastructures, compact urban form, and transport planning can encourage higher population densities and subsequently avoid lock-in of high carbon emission patterns for travel. The results underscore a significant potential urbanization wedge for reducing energy use in rapidly urbanizing Asia, Africa, and the Middle East.

Changing global patterns of urban exposure to flood and drought hazards

Abstract: The studies that quantify the human and economic costs of increasing exposure of cities to various natural hazards consider climate change together with increasing levels of population and economic activity, but assume constant urban extent. Accurate estimates of the potential losses due to changing exposure of cities, however, require that we know where they will grow in the future. Here, we present the first-ever estimates of the changing exposure of urban infrastructure to floods and droughts due to urban land expansion from 2000 to 2030. The percentage of the global urban land that lies within the low elevation coastal zone (LECZ) increases only slightly to 13% by 2030; nonetheless, this corresponds to a 230% increase in the amount of urban land within the LECZ (from 71,000 km 2 to 234,000 km 2 ). In 2000, about 30% of the global urban land (i.e., nearly 200,000 km 2 ) was located in the high-frequency flood zones; by 2030, this will reach 40% (i.e., over 700,000 km 2 ). The emerging coastal metropolitan regions in Africa and Asia will be larger than those in the developed countries and will have larger areas exposed to flooding. The urban extent in drylands will increase by nearly 300,000 km 2 , reaching almost 500,000 km 2 . Overall, without factoring in the potential impacts from climate change, the extent of urban areas exposed to flood and drought hazards will increase, respectively, 2.7 and almost 2 times by 2030. Globally, urban land exposed to both floods and droughts is expected to increase over 250%. There are significant geographical variations in the rates and magnitudes of urban expansion exposed to floods or droughts or both. Several policy options exist to safeguard urban infrastructure from flood and drought hazards. These range from directing development away from flood- or drought-prone zones to large-scale adoption of “green infrastructure” (or “eco-efficient infrastructure”). Decisions, taken today on managing urban growth in locations exposed to these hazards, can make a big difference in mitigating likely losses due to floods and droughts in the near future.

Urban vegetable for food security in cities. A review

Abstract: Global food production faces great challenges in the future. With a future world population of 9.6 billion by 2050, rising urbanization, decreasing arable land, and weather extremes due to climate change, global agriculture is under pressure. While today over 50 % of the world population live in cities, by 2030, the number will rise to 70 %. In addition, global emissions have to be kept in mind. Currently, agriculture accounts for around 20–30 % of global greenhouse gas emissions. Shifting food production to locations with high demands reduces emissions and mitigates climate change. Urban horticulture increases global food production by exploiting new locations for cultivation. However, higher land prices and urban pollution constrain urban horticulture. In this paper, we review different urban cultivation systems throughout the world. Our main findings from ecological, economical, and social aspects are: (1) Urban horticulture activities are increasing globally with at least 100 million people involved worldwide. With potential yields of up to 50 kg per m2 per year and more, vegetable production is the most significant component of urban food production which contributes to global food security. (2) Organoponic and other low-input systems will continue to play an important role for a sustainable and secure food production in the future. (3) Despite the resource efficiency of indoor farming systems, they are still very expensive. (4) Integrating urban horticulture into educational and social programs improves nutrition and food security. Overlaying these, new technologies in horticultural research need to be adopted for urban horticulture to increase future efficiency and productivity. To enhance sustainability, urban horticulture has to be integrated into the urban planning process and supported through policies. However, future food production should not be “local at any price,” but rather committed to increase sustainability.

A global map of urban extent from nightlights

Abstract: Urbanization, a major driver of global change, profoundly impacts our physical and social world, for example, altering not just water and carbon cycling, biodiversity, and climate, but also demography, public health, and economy. Understanding these consequences for better scientific insights and effective decision-making unarguably requires accurate information on urban extent and its spatial distributions. We developed a method to map the urban extent from the defense meteorological satellite program/operational linescan system nighttime stable-light data at the global level and created a new global 1 km urban extent map for the year 2000. Our map shows that globally, urban is about 0.5% of total land area but ranges widely at the regional level, from 0.1% in Oceania to 2.3% in Europe. At the country level, urbanized land varies from about 0.01 to 10%, but is lower than 1% for most (70%) countries. Urbanization follows land mass distribution, as anticipated, with the highest concentration between 30° N and 45° N latitude and the largest longitudinal peak around 80° W. Based on a sensitivity analysis and comparison with other global urban area products, we found that our global product of urban areas provides a reliable estimate of global urban areas and offers the potential for producing a time-series of urban area maps for temporal dynamics analyses.

An Ecology for Cities: A Transformational Nexus of Design and Ecology to Advance Climate Change Resilience and Urban Sustainability

Abstract: Cities around the world are facing an ever-increasing variety of challenges that seem to make more sustainable urban futures elusive. Many of these challenges are being driven by, and exacerbated by, increases in urban populations and climate change. Novel solutions are needed today if our cities are to have any hope of more sustainable and resilient futures. Because most of the environmental impacts of any project are manifest at the point of design, we posit that this is where a real difference in urban development can be made. To this end, we present a transformative model that merges urban design and ecology into an inclusive, creative, knowledge-to-action process. This design-ecology nexus—an ecology for cities—will redefine both the process and its products. In this paper we: (1) summarize the relationships among design, infrastructure, and urban development, emphasizing the importance of joining the three to achieve urban climate resilience and enhance sustainability; (2) discuss how urban ecology can move from an ecology of cities to an ecology for cities based on a knowledge-to-action agenda; (3) detail our model for a transformational urban design-ecology nexus, and; (4) demonstrate the efficacy of our model with several case studies.

Vulnerability to heat waves: Impact of urban expansion scenarios on urban heat island and heat stress in Paris (France)

Abstract: The evolution of heat-wave risk in cities is related to regional climate change in interaction with urban heat island. Land planning and urban transport policies, due to their long-lasting impact on city's size and shape, can also have an influence. However, these combined effects are complex and strongly depend on the indicators used to quantify heat-wave risk. With Paris area as a case study and using an interdisciplinary modelling chain, including a socio-economic model of land-use transport interaction and a physically-based model of urban climate, air temperature in the city during heat waves is simulated for five urban expansion scenarios. The urban heat island is always higher at night and affects preferentially the city centre. Its intensity and spatial extension are moderately impacted by densification process and choice in urban form. But the variation of heat-wave risk with the densification dynamics is not limited to the effect on urban heat island, and also depends on exposure to heat of population. Spatial distribution of population in the city differs according to urban expansion scenarios. The results show that the compact city, by concentrating the inhabitants in areas the most impacted by heat island effect, amplifies the overall vulnerability of population. © 2015 The Authors.

ARC3.2 Summary for City Leaders Climate Change and Cities: Second Assessment Report of the Urban Climate Change Research Network

Abstract: ARC3.2 presents a broad synthesis of the latest scientific research on climate change and cities. Mitigation and adaptation climate actions of 100 cities are documented throughout the 16 chapters, as well as online through the ARC3.2 Case Study Docking Station. Pathways to Urban Transformation, Major Findings, and Key Messages are highlighted here in the ARC3.2 Summary for City Leaders. These sections lay out what cities need to do achieve their potential as leaders of climate change solutions. UCCRN Regional Hubs in Europe, Latin America, Africa, Australia and Asia will share ARC3.2 findings with local city leaders and researchers. The ARC3.2 Summary for City Leaders synthesizes Major Findings and Key Messages on urban climate science, disasters and risks, urban planning and design, mitigation and adaptation, equity and environmental justice, economics and finance, the private sector, urban ecosystems, urban coastal zones, public health, housing and informal settlements, energy, water, transportation, solid waste, and governance. These were based on climate trends and future projections for 100 cities around the world.

Urbanization promotes non-native woody species and diverse plant assemblages in the New York metropolitan region

Abstract: The rapid urbanization of the world has significant ecological consequences that shape global biodiversity patterns. The plant communities now common in urban centers may represent new habitats with unique dynamics and the potential for highly modified ecological services. This study, joining extensive spatial and floristic data sets, examined current distribution patterns of non-native and native woody plant species in the New York metropolitan region, USA. We joined the New York Metropolitan Flora (NYMF) database of woody species with GIS data of urban land cover for 297 5 km by 5 km landscape blocks. We tested the relationship between urbanization and native and non-native species richness patterns, the extent of non-native species presence in the urban area, and the change in beta diversity across a gradient of urban land cover. We found that across the urban–rural gradient, native plant species richness decreased and non-native species richness increased with increasing urban land cover. Total richness does not change across the urban–rural gradient. Our analyses show that these patterns are highly correlated with urbanization, but vary across the New Jersey landscape. We also found an increase in beta diversity with urbanization; urban areas are not homogenized in plant species composition compared to rural areas. Here we show a species-rich flora dominated by non-native species which are differentiating the urban flora. These results can help guide appropriate conservation decisions for the maintenance of plant biodiversity in cities.

Contrasting responses of urban and rural surface energy budgets to heat waves explain synergies between urban heat islands and heat waves

Abstract: Heat waves (HWs) are projected to become more frequent and last longer over most land areas in the late 21st century, which raises serious public health concerns. Urban residents face higher health risks due to synergies between HWs and urban heat islands (UHIs) (i.e., UHIs are higher under HW conditions). However, the responses of urban and rural surface energy budgets to HWs are still largely unknown. This study analyzes observations from two flux towers in Beijing, China and reveals significant differences between the responses of urban and rural (cropland) ecosystems to HWs. It is found that UHIs increase significantly during HWs, especially during the nighttime, implying synergies between HWs and UHIs. Results indicate that the urban site receives more incoming shortwave radiation and longwave radiation due to HWs as compared to the rural site, resulting in a larger radiative energy input into the urban surface energy budget. Changes in turbulent heat fluxes also diverge strongly for the urban site and the rural site: latent heat fluxes increase more significantly at the rural site due to abundant available water, while sensible heat fluxes and possibly heat storage increase more at the urban site. These comparisons suggest that the contrasting responses of urban and rural surface energy budgets to HWs are responsible for the synergies between HWs and UHIs. As a result, urban mitigation and adaption strategies such as the use of green roofs and white roofs are needed in order to mitigate the impact of these synergies.

Spatial variation of the daytime Surface Urban Cool Island during the dry season in Erbil, Iraqi Kurdistan, from Landsat 8

Abstract: Differences between the energy balance of cities and their non-urban surroundings exist due to modification of surface properties. In temperate and sub-tropical climates, these differences are manifest as the Urban Heat Island (UHI) effect. However in more arid environments man-made modifications of the environment can cause urban cooling relative to the surrounding landscape particularly during the dry season. This research examines the spatial formation of the daytime Surface Urban Cool Island (SUCI) effect of Erbil city in Iraq, as a case study of cities in semi-arid climates. Six satellite images acquired by Landsat 8 during the period from 1st July to 19th September 2013 are used to retrieve Land Surface Temperature (LST), identify Land Use/Land Cover (LULC) classes and investigate the spatial variation of LST and the SUCI intensity. In order to find out the key drivers of the observed patterns of LST, the relationship with wetness, brightness, bareness, built-up and vegetation index maps are examined. The results indicate that densely built-up areas, such as central districts of the city, green areas and water bodies, had lower LST acting as cool islands, compared to the non-urbanized area around the city. In contrast, the airport, open spaces and new low-density housing developments on the outskirts of the city, experienced higher LST and showed an SUHI effect. A very strong inverse relationship is evident between surface temperature and wetness index (r = −0.9; p < 0.01). A strong positive correlation (r = 0.75; p < 0.00001) is apparent with the brightness index. In contrast, between surface temperature and the greenness index a moderate negative correlation was found (r = −0.39; p < 0.01) for a typical dry season day. The results show that during the daytime residential areas in the city centre recorded an LST of 46.2 ± 1.74 °C. Urban Cool Island Intensity (UCII) of the city ranged from 3.5 to 4.6 °C compared to a 10 km buffer zone around the city. This study shows that during the dry season in some cities, such as Erbil, the surface wetness is the main determinant of the UCI effect, and not vegetation cover.

What are hot and what are not in an urban landscape: quantifying and explaining the land surface temperature pattern in Beijing, China

Abstract: Understanding how landscape components affect the urban heat islands is crucial for urban ecological planning and sustainable development. The purpose of this study was to quantify the spatial pattern of land surface temperatures (LSTs) and associated heat fluxes in relation to land-cover types in Beijing, China, using portable infrared thermometers, thermal infrared imagers, and the moderate resolution imaging spectroradiometer. The spatial differences and the relationships between LSTs and the hierarchical landscape structure were analyzed with in situ observations of surface radiation and heat fluxes. Large LST differences were found among various land-use/land-cover types, urban structures, and building materials. Within the urban area, the mean LST of urban impervious surfaces was about 6–12 °C higher than that of the urban green space. LSTs of built-up areas were on average 3–6 °C higher than LSTs of rural areas. The observations for surface radiation and heat fluxes indicated that the differences were caused by different fractions of sensible heat or latent heat flux in net radiation. LSTs decreased with increasing elevation and normalized difference vegetation index. Variations in building materials and urban structure significantly influenced the spatial pattern of LSTs in urban areas. By contrast, elevation and vegetation cover are the major determinants of the LST pattern in rural areas. To alleviate urban heat island intensity, urban planners and policy makers should pay special attention to the selection of appropriate building materials, the reasonable arrangement of urban structures, and the rational design of landscape components.

The Urban Climate Challenge : Rethinking the Role of Cities in the Global Climate Regime

Abstract: Selected Contents: Part 1: Governing the Urban Climate Challenge: Understanding the Role of Cities in the Global Climate Regime 1. Introduction: Urban Resilience, Low Carbon Governance and the Global Climate Regime Craig Johnson, Noah Toly, and Heike Schroeder 2. Bringing Cities into the Global Climate Framework Saskia Sassen 3. Closed Cycles - Open City Katleen De Flander Part 2: Going Global? The Changing Face of Urban Climate Governance 4. If Cities are the Solution, What are the Problems? The Promise and Perils of Urban Climate Leadership David Gordon and Michele Acuto 5. Multinational Companies and Urban Climate Governance: Market Making or Successful Policy Innovation? Sofie Bouteligier Part 3: Domestic Policy Responses: Integrating Mitigation and Adaptation into Urban Climate Governance 6. Combining Local and Transnational Action in the Adoption and Implementation of Climate Policies in the City of Sao Paulo Joana Setzer, Laura Valente de Macedo, and Fernando Rei 7. Urban Climate Governance Through a Sustainability Lens: Exploring the Integration of Adaptation and Mitigation in Four British Columbian Cities Sarah Burch, Alison Shaw, Freya Kristensen, John Robinson, and Ann Dale 8. Climate Change Adaptation in Mumbai, India Emily Boyd, Aditya Ghosh, Maxwell T. Boykoff 9. Relational Agency and the Local Governance of Climate Change: A Case Study of Portland, Oregon Alex Aylett Part 4: Regional Policy Perspectives: Comparing Policies and Outcomes across Regional Policy Regimes 10. Multilevel Governance and Institutional Capacity for Climate Change Responses in Latin American Cities Patricia Romero-Lankao, Geogelina Hardoy, Sara Hughes, Daniel Gnatz, Angelica Rosas-Huerta, and Roxana Borquez 11. Climate Change Adaptation and African Cities: Understanding the Impact of Government and Governance on Future Action Christopher Gore Part 5: Governing the Urban Climate Challenge: New Directions in Theory, Policy and Research 12. Conclusion: Governing the Urban Climate Challenge Craig Johnson, Noah Toly, Heike Schroeder

Observed Spatial Characteristics of Beijing Urban Climate Impacts on Summer Thunderstorms

Abstract: This study investigates interactive effects from the Beijing urban area on temperature, humidity, wind speed and direction, and precipitation by use of hourly automatic weather station data from June to August 2008–12. Results show the Beijing summer urban heat island (UHI) as a multicenter distribution (corresponding to underlying land-use features), with stronger nighttime than daytime values (averages of 1.7° vs 0.8°C, respectively). Specific humidity was lower in urban Beijing than in surrounding nonurban areas, and this urban dry island is stronger during day than night (maximum of −2.4 vs −1.9 g kg−1). Wind direction is affected by both a mountain–valley-breeze circulation and by urbanization. Morning low-level flows converged into the strong UHI, but afternoon and evening southerly winds were bifurcated by an urban building-barrier-induced divergence. Summer thunderstorms also thus bifurcated and bypassed the urban center because of the building-barrier effect during both daytime and nightt...

Public participation, civic capacity, and climate change adaptation in cities

Abstract: Cities are increasingly involved in planning for climate change adaptation, although the extent and role of public participation in such efforts remains poorly theorized and understudied. This paper employs a case survey methodology to systematically review the recent literature on urban climate change adaptation with respect to public participation, stakeholder engagement, and civic capacity. Six forms of participation in urban adaptation are identified from the literature and the distinguishing characteristics and use of each type are examined across the cases. Few cases illustrate robust and sustained civic capacity in the governance of urban climate adaptation, although several cases reveal budding capacity that could emerge with further efforts to engage businesses and citizens in articulating priorities and strategies for future adaptation efforts.

The New Global Urban Realm: Complex, Connected, Diffuse, and Diverse Social-Ecological Systems

Abstract: Urbanization continues to be a transformative process globally, affecting ecosystem integrity and the health and well being of people around the world. Although cities tend to be centers for both the production and consumption of goods and services that degrade natural environments, there is also evidence that urban ecosystems can play a positive role in sustainability efforts. Despite the fact that most of the urbanization is now occurring in the developing countries of the Global South, much of what we know about urban ecosystems has been developed from studying cities in the United States and across Europe. We propose a conceptual framework to broaden the development of urban ecological research and its application to sustainability. Our framework describes four key contemporary urban features that should be accounted for in any attempt to build a unified theory of cities that contributes to urban sustainability efforts. We evaluated a range of examples from cities around the world, highlighting how urban areas are complex, connected, diffuse and diverse and what these interconnected features mean for the study of urban ecosystems and sustainability.

The impact of vegetation on urban microclimate to counterbalance built density in a subtropical changing climate

Abstract: The purpose of this research is to assess the microscale cooling effects of vegetation in urban environment, especially during daytime, to counterbalance urban warming effects resulting from an increase in built density in a subtropical climate. Considering that Brazil’s climate will be warmer in the coming decades, the paper presents a brief review of planning with high-density and urban greening, having in mind that even low-density land use can contribute to urban heating, depending on the urban occupation pattern. In high-density cities, the most important vegetation effect is to prevent heating in urban canyons, decreasing solar radiation absorption by shading and evapotranspiration. Parametric studies exploring different scenarios of high-density urban blocks and greening have been carried out to investigate different distributions of dense trees to ameliorate urban microclimate using ENVI-met V4 Preview I, previously calibrated with field measurements of local climate and vegetation data. Aiming to benefit urban activities, air, surface and mean radiant temperatures at the pedestrian level are compared among different greening strategies and built densities’ scenarios. Based on the results, two outdoor comfort indexes TEP –Temperature of Equivalent Perception and PET – Physiological Equivalent Temperature were applied to verify the contribution of vegetation to better comfort conditions.

Malthus living in a slum: Urban concentration, infrastructures and economic growth

Abstract: The link between urban concentration and economic growth at country level is not straightforward, as there are benefits as well as costs associated with urban concentration. Indeed, recent empirical evidence suggests different effects of urban concentration on growth depending on the level of development and the world region under analysis. This paper revisits the literature on urban concentration and economic growth to shed some light on these previous results. In particular, differences in the process of urbanisation, and in the quality of the urban environment itself, have been suggested as most likely defining the balance between benefits and costs from urban concentration, and are probably behind differences in the relationship between concentration and growth. However, empirical evidence in this regard remains very limited. The aim of the paper is to fill this gap by paying special and explicit attention to differences between world regions in terms of urban infrastructure, essentially access to basic urban services. The main contribution of the paper is to therefore provide empirical evidence on the role that the urban environment plays in the relationship between urban concentration and economic growth.

Do cities simulate climate change? A comparison of herbivore response to urban and global warming

Abstract: Cities experience elevated temperature, CO2, and nitrogen deposition decades ahead of the global average, such that biological response to urbanization may predict response to future climate change. This hypothesis remains untested due to a lack of complementary urban and long-term observations. Here, we examine the response of an herbivore, the scale insect Melanaspis tenebricosa, to temperature in the context of an urban heat island, a series of historical temperature fluctuations, and recent climate warming. We survey M. tenebricosa on 55 urban street trees in Raleigh, NC, 342 herbarium specimens collected in the rural southeastern United States from 1895 to 2011, and at 20 rural forest sites represented by both modern (2013) and historical samples. We relate scale insect abundance to August temperatures and find that M. tenebricosa is most common in the hottest parts of the city, on historical specimens collected during warm time periods, and in present-day rural forests compared to the same sites when they were cooler. Scale insects reached their highest densities in the city, but abundance peaked at similar temperatures in urban and historical datasets and tracked temperature on a decadal scale. Although urban habitats are highly modified, species response to a key abiotic factor, temperature, was consistent across urban and rural-forest ecosystems. Cities may be an appropriate but underused system for developing and testing hypotheses about biological effects of climate change. Future work should test the applicability of this model to other groups of organisms.

The Influence of Drivers and Barriers on Urban Adaptation and Mitigation Plans-An Empirical Analysis of European Cities.

Abstract: Cities are recognised as key players in global adaptation and mitigation efforts because the majority of people live in cities. However, in Europe, which is highly urbanized and one of the most advanced regions in terms of environmental policies, there is considerable diversity in the regional distribution, ambition and scope of climate change responses. This paper explores potential factors contributing to such diversity in 200 large and medium-sized cities across 11 European countries. We statistically investigate institutional, socio-economic, environmental and vulnerability characteristics of cities as potential drivers of or barriers to the development of urban climate change plans. Our results show that factors such as membership of climate networks, population size, GDP per capita and adaptive capacity act as drivers of mitigation and adaptation plans. By contrast, factors such as the unemployment rate, warmer summers, proximity to the coast and projected exposure to future climate impacts act as barriers. We see that, overall, it is predominantly large and prosperous cities that engage in climate planning, while vulnerable cities and those at risk of severe climate impacts in the future are less active. Our analysis suggests that climate change planning in European cities is not proactive, i.e. not significantly influenced by anticipated future impacts. Instead, we found that the current adaptive capacity of a city significantly relates to climate planning. Along with the need to further explore these relations, we see a need for more economic and institutional support for smaller and less resourceful cities and those at high risk from climate change impacts in the future.