What is an urban heat island?
Scientists often mention the “urban heat island effect.” They are referring to the fact that cities are often hotter than the surrounding areas because the asphalt in our streets and the concrete in our buildings retain heat. In contrast, areas like the suburbs that have more trees, more grass, and relatively less concrete tend to be cooler. For PLANYC, we have measured this effect here in New York and the City is generally five degrees Fahrenheit hotter on a summer day than the surrounding suburbs.
Urban heat islands are urban areas that are hotter than surrounding rural areas. Factors that contribute to heat islands include the removal of local vegetation and natural surfaces as well as the addition of heat absorbing surfaces like dark roofs and pavements. Many US cities are urban heat islands with temperatures between 2 and 15 Fahrenheit hotter than their surroundings (Akbari 1996). Utah urban areas that are landscaped present a special case because much of the surrounding areas are actually dry, hot desert. However, within Utah urban areas there are localized high-temperature patches caused by the same factors that cause urban heat islands. Urban heat islands are expanding with spreading populations and new building construction. Since 1940, summertime temperatures of many cities have climbed steadily by 0.25 to 1 degree Fahrenheit per decade (Akbari, 1994). As temperatures increase, the need for air conditioning increases, this places more demand for power generation. Los Ang
