Large-scale warming is not urban. Nature

Hadley Centre, Meteorological Office, Exeter EX1 3PB, UK.
Nature (Impact Factor: 41.46). 12/2004; 432(7015):290. DOI: 10.1038/432290a
Source: PubMed

ABSTRACT Controversy has persisted over the influence of urban warming on reported large-scale surface-air temperature trends. Urban heat islands occur mainly at night and are reduced in windy conditions. Here we show that, globally, temperatures over land have risen as much on windy nights as on calm nights, indicating that the observed overall warming is not a consequence of urban development.

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    • "Cities accommodate over 50% of the world's population (Jansson, 2013). While some may have suggested that urbanisation has limited to no effect with respect to climate change (Parker, 2004; Peterson, 2003), some others indicate that cities are effectively capable of responding to it (Emmanuel & Krüger, 2012; Hoornweg, Bhada, Freire, Trejos, & Sugar, 2010; Moss, 2009). Nevertheless , cities now contribute to 60–85% of the world's energy consumption (Kamal-Chaoui & Roberts, 2009; Nakicenovic & Swart, 2000) and it is not credulous to expect that concentration of energy consemption activities on an over-crowded high-density area of land, have an impact on at least local, if not global, warming . "
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    ABSTRACT: Urbanisation may have been shown to have no effect on climate change, but some researchers suggest that cities are fully capable of responding to it. Urban Heat Islands (UHIs) represent dense urban areas within cities where the temperature is recorded to be higher than the neighbouring areas or those located in suburbia. Mitigation of UHI effects can help diminish detriments of climate change. This paper sets out to establish UHI mitigation strategies, their effectiveness and resilience to help provide recommendations for application of such strategies in future. Existing literature suggest that UK is facing with growing problem of UHI effects and sustainable development at urban scale can be improved if proportionate measures are taken to mitigate those effects. The lack of guidance for designers and planners with regards to UHI mitigation is also indicated in the literature where trees, shrubs and grass (TSG), use of high albedo materials (HAM) in external building surfaces and urban inland water bodies (UIWB) are identified as effective measures to mitigate UHI. This research identifies and tests resilience and effectiveness of UHI mitigation strategies, using ENVI-met simulations and through Urban Futures Assessment Method (UFAM). Assessed mitigation strategies (TSG, HAM, UIWB) are shown to have a similar level of resilience which could be improved if proper future-proof measures are taken in place. As a result, some practical suggestions are provided to help improve the resilience of tested UHI mitigation strategies in this study.
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    • "Greenhouse gas emissions are embedded in climate models for IPCC climate change assessments, and land-cover changes in forcing scenarios for future climate change studies are also documented (Feddema et al., 2005). In recent years, there has been growing interest in land-use/land-cover change and its effect on climate change (Kalnay and Cai, 2003; Roy et al., 2003; Parker, 2004; Pitman et al., 2004; Feddema et al., 2005; Lobell et al., 2006a, 2008; Kueppers et al., 2007; Deo et al., 2009; Hu et al., 2010). "
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    ABSTRACT: Irrigation and urbanization, two widely occurring land-use/land-cover changes, have important influences on regional climate, especially on temperature. The effect of irrigation and urbanization on temperature is separately documented in several studies. However, there are few studies analysing the combined effects of irrigation and urbanization on temperature. In this study, changes in surface temperature were analysed in relation to irrigation and urbanization on the Huang-Huai-Hai Plain of China from 1955 to 2007. To better characterize the combined effects of these two processes on temperatures, long-term weather observations are used along with irrigation and urbanization data sets. The results indicated that irrigation had a significant cooling effect of 0.17–0.20 °C decade−1 on average daily maximum temperature of the hottest 1, 5, and 30 d of each year on the Huang-Huai-Hai Plain. Compared with the reference conditions, irrigation also indicated a cooling effect of 0.12 °C decade−1 on summertime daily maximum temperature. In contrast to its effect on maximum temperature, irrigation appeared to induce a warming effect of 0.43 °C/decade on average daily minimum temperature of the coldest 1 d of each year. Where irrigation interfaced with urbanization, the urbanization warming of extreme daily maximum temperature seemed to only partly counteract the irrigation cooling effect. The findings of this study deepen our insight into the effects of irrigation and urbanization on temperature dynamics, and the combined implications for regional climate change. Further efforts to understand irrigation and urbanization effects on climate should not only use observations, but should also be coupled with dynamic land-use and regional climate models to understand the complex processes and controlling mechanisms.
    International Journal of Climatology 03/2014; 34(4). DOI:10.1002/joc.3755 · 3.16 Impact Factor
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    • "Marked progress has been made internationally in the study of impacts of urbanization on mean surface air temperatures. At the global scale, it is generally agreed that the contribution of urbanization to global warming is limited (Jones et al. 1990; Peterson 2003; Parker 2004; Hansen et al. 2010; Brohan et al. 2006). At the regional scale, the climatic impact of UHI is more significant. "
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    ABSTRACT: Although previous studies show that urbanization contributes to less than 10 % of the long-term regional total warming trend of mean surface air temperature in northeast China (Li et al. 2010), the urban heat island (UHI) impact on extreme temperatures could be more significant. This paper examines the urbanization impact on extreme winter minimum temperatures from 33 stations in North China during the period of 1957–2010. We use the Generalized Extreme Value (GEV) distribution to analyze the distribution of extreme minimum temperatures and the long-term variations of the three distributional characteristics parameters. Results suggest that among the three distribution parameters, the position parameter is the most representative in terms of the long-term extreme minimum temperature change. A new classification method based on the intercommunity (factors analysis method) of the temperature change is developed to detect the urbanization effect on winter extreme minimum temperatures in different cities. During the period of rapid urbanization (after 1980), the magnitude of variations of the three distribution parameters for the urban station group is larger than that for the reference station group, indicating a higher chance of occurrence of warmer weather and a larger fluctuation of temperatures. Among different types of cities, the three parameters of extreme minimum temperature distribution of the urban station group are, without exception, higher than those of the reference station group. The urbanization of different types of cities all show a warming effect, with small-size cities have the most evident effects on extreme minimum temperatures.
    Climatic Change 11/2013; 122(4). DOI:10.1007/s10584-013-1013-z · 3.43 Impact Factor
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