Urban climate

About: Urban climate is a research topic. Over the lifetime, 4992 publications have been published within this topic receiving 166644 citations.

A survey of urban climate change experiments in 100 cities

Abstract: Cities are key sites where climate change is being addressed. Previous research has largely overlooked the multiplicity of climate change responses emerging outside formal contexts of decision-making and led by actors other than municipal governments. Moreover, existing research has largely focused on case studies of climate change mitigation in developed economies. The objective of this paper is to uncover the heterogeneous mix of actors, settings, governance arrangements and technologies involved in the governance of climate change in cities in different parts of the world. The paper focuses on urban climate change governance as a process of experimentation. Climate change experiments are presented here as interventions to try out new ideas and methods in the context of future uncertainties. They serve to understand how interventions work in practice, in new contexts where they are thought of as innovative. To study experimentation, the paper presents evidence from the analysis of a database of 627 urban climate change experiments in a sample of 100 global cities. The analysis suggests that, since 2005, experimentation is a feature of urban responses to climate change across different world regions and multiple sectors. Although experimentation does not appear to be related to particular kinds of urban economic and social conditions, some of its core features are visible. For example, experimentation tends to focus on energy. Also, both social and technical forms of experimentation are visible, but technical experimentation is more common in urban infrastructure systems. While municipal governments have a critical role in climate change experimentation, they often act alongside other actors and in a variety of forms of partnership. These findings point at experimentation as a key tool to open up new political spaces for governing climate change in the city.

Strong contributions of local background climate to urban heat islands

Abstract: Climate modelling is used to show that for cities across North America, geographic variations in daytime urban heat islands—that is, the temperature differences between urban and adjacent rural areas—are largely explained by variations in the efficiency with which those areas convect heat to the lower atmosphere. It is often warmer in a city than in the surrounding rural areas, sometimes by up to a few degrees. This urban heat island effect is commonly explained as a consequence of a lower rate of evaporative cooling in urban areas. But here Xuhui Lee and colleagues use climate modelling to show that for cities across North America, the daytime urban heat island effect varies with the efficiency of heat convection between the land surface and the lower atmosphere. The convection effect varies with climate regime, causing significant urban warming in wet climates but cooling in dry climates. Aerodynamics also play a part, and if urban areas are aerodynamically smoother than surrounding rural areas, urban heat dissipation is less efficient and warming occurs. The health impact of heatwaves means that mitigation of the heat island effect may be beneficial. The authors suggest that aerodynamic spoilers — a city-wide increase in building height for instance — may be impractical. But efforts to increase urban albedo, by installing reflective roofs for instance, might be worth pursuing. The urban heat island (UHI), a common phenomenon in which surface temperatures are higher in urban areas than in surrounding rural areas, represents one of the most significant human-induced changes to Earth’s surface climate1,2. Even though they are localized hotspots in the landscape, UHIs have a profound impact on the lives of urban residents, who comprise more than half of the world’s population3. A barrier to UHI mitigation is the lack of quantitative attribution of the various contributions to UHI intensity4 (expressed as the temperature difference between urban and rural areas, ΔT). A common perception is that reduction in evaporative cooling in urban land is the dominant driver of ΔT (ref. 5). Here we use a climate model to show that, for cities across North America, geographic variations in daytime ΔT are largely explained by variations in the efficiency with which urban and rural areas convect heat to the lower atmosphere. If urban areas are aerodynamically smoother than surrounding rural areas, urban heat dissipation is relatively less efficient and urban warming occurs (and vice versa). This convection effect depends on the local background climate, increasing daytime ΔT by 3.0 ± 0.3 kelvin (mean and standard error) in humid climates but decreasing ΔT by 1.5 ± 0.2 kelvin in dry climates. In the humid eastern United States, there is evidence of higher ΔT in drier years. These relationships imply that UHIs will exacerbate heatwave stress on human health in wet climates where high temperature effects are already compounded by high air humidity6,7 and in drier years when positive temperature anomalies may be reinforced by a precipitation–temperature feedback8. Our results support albedo management as a viable means of reducing ΔT on large scales9,10.

The urban heat island and its impact on heat waves and human health in Shanghai

Abstract: With global warming forecast to continue into the foreseeable future, heat waves are very likely to increase in both frequency and intensity. In urban regions, these future heat waves will be exacerbated by the urban heat island effect, and will have the potential to negatively influence the health and welfare of urban residents. In order to investigate the health effects of the urban heat island (UHI) in Shanghai, China, 30 years of meteorological records (1975-2004) were examined for 11 first- and second-order weather stations in and around Shanghai. Additionally, automatic weather observation data recorded in recent years as well as daily all-cause summer mortality counts in 11 urban, suburban, and exurban regions (1998-2004) in Shanghai have been used. The results show that different sites (city center or surroundings) have experienced different degrees of warming as a result of increasing urbanization. In turn, this has resulted in a more extensive urban heat island effect, causing additional hot days and heat waves in urban regions compared to rural locales. An examination of summer mortality rates in and around Shanghai yields heightened heat-related mortality in urban regions, and we conclude that the UHI is directly responsible, acting to worsen the adverse health effects from exposure to extreme thermal conditions.

Climate considerations in building and urban design

Abstract: BUILDING CLIMATOLOGY. Comfort Issues and Climate Analysis for Building Design. Architectural Features Affecting the Indoor Climate. Materials Properties and Thermal Performance of Buildings. Passive Solar Heating Systems. Passive Cooling of Buildings. Climatic Characteristics of Housing Types. URBAN CLIMATOLOGY. General Characteristics of the Urban Climate. Urban Design Effects on the Urban Climate. Impact of Green Areas on Site and Urban Climates. BUILDING AND URBAN DESIGN GUIDELINES. Building and Urban Design for Hot-Dry Regions. Building and Urban Design for Hot-Humid Regions. Building and Urban Design in Cold Climates. Regions with Cold Winters and Hot-Humid Summers. Index.