Cooling Heat Islands

According to the United Nation report “World Urbanization Prospects”, 54% (about 3.9 billion) of the world’s population residing in urban areas in 2014. The urban population is expected to grow to 66% (about 6.3 billion) by 2050. In addition to encountering many challenges of global climate change, urban inhabitants face many problems associated with urban heat islands (UHI) such as higher outdoor summertime temperatures, higher urban air pollutions, higher demands for air conditioning, and higher heat stress-related mortalities, to name a few. Although the migration to urban areas is caused by macro and global economic drives and little can be done to reverse the trend in the short-term, the policy makers can design effective urban growth policies to mitigate the detrimental effects of UHIs. The Third International Conference on Countermeasures to Urban Heat Island held in Venice, Italy in October 2014 brought together the community of scholars and policy makers to focus on development of effective countermeasures to UHIs. Over 160 papers discussing advances in both policy and science of UHI countermeasures were presented in the Venice conference. A group of high-quality papers focusing on issues related to the effect of UHI on buildings energy use are published in a special issue of Energy and Buildings. Fifteen other high-quality papers related to urban climate are collected in this special issue of Urban Climate. Papers included in this special issue address: Quantification and monitoring of urban heat islands and effects on urban climate Sismanidis; Keramitsoglou, and Kiranoudis discuss a satellite-based system for continuous monitoring of surface UHIs Kaloustian and Diab present the results of an analysis on the effects of urbanization on the UHI in Beirut Polydoros and Cartalis assess the impact of urban expansion to the state of thermal environment of peri-urban areas using indices Rasul, Balzter, and Smith analyze the spatial variation of the daytime surface urban cool island during the dry season in Erbil, Iraqi Kurdistan, from Landsat 8 Analysis of the effects of urban-scale countermeasure technologies Noro and Lazzarin present the results of simulation analysis of the effect of UHI mitigation strategies in Padua, Italy Ruiz, Sosa, Correa, and Cantón discuss suitable configurations for forested urban canyons to mitigate the UHI in the city of Mendoza, Argentina Musy, Malys, Morille, and Inard evaluate the use of SOLENE-microclimate model to assess adaptation strategies at the district scale Duarte, Shinzato, Gusson, and Alves evaluate the impact of vegetation on urban microclimate to counterbalance built density in a subtropical changing climate Yoshida, Hisabayashi, Kashihara, Kinoshita, and Hashida evaluate the effect of tree canopy on urban thermal environment Lobaccaro, and Acero present a comparative analysis of green actions to improve outdoor thermal comfort inside typical urban street canyons Botham-Myint, Recktenwald, and Sailor discuss the thermal footprint effect of rooftop urban cooling strategies Simplified methods to quantify the effect of UHI countermeasure Touchaei and Akbari discuss a method to evaluate the seasonal effect of increasing albedo on urban climate and energy Pomerantz, Rosado and Levinson outline a simple tool for estimating city-wide annual electrical energy savings from cooler surfaces Innovative methods to improve urban outdoor thermal comfort Kleerekoper, van dan Dobbelsteen, van den Ham, Hordijk, and Martin explore a new climate adaptation technique by proposing colored façades to create drafts in urban settings Castaldo presents results of a thermal-energy analysis of natural “cool” stone aggregates as passive cooling and global warming mitigation technique Editors of this special issue, Cooling Heat Islands, hope that this collection will further contribute to development of policy plans to counter UHI. The efforts in cooling heat islands is ever expanding; the Fourth International Conference on Countermeasures to Urban Heat Island to be held in Singapore from May 30th to June 1st, 2016 has attracted substantially more attention from both scholars and policy makers with over 300 abstracts submitted as of the date of this editorial (31 October 2015). Change only happens with good data and analyses, strong leadership, and persistence. Let us work towards cooling our urban heat islands that saves us money in reducing air conditioning energy use, improves ambient air quality and comfort, reduces heat stress related mortality, and cools the globe all with little or no incremental cost. A deal hard to pass.