Countermeasures to Urban Heat Islands: A Global View

Conference · Mon Jul 17 04:00:00 EDT 2006

OSTI ID:926307

Meier, Alan

An important milestone was passed this year when the fraction of the world's population living in cities exceeded 50%. This shift from the countryside to urban areas is certain to continue and, for many, the destination will be large cities. Already there are over 400 cities with populations greater than one million inhabitants and twenty cities with populations greater than ten million inhabitants. With a growing fraction of the population living in an urban environment, the unique aspects of an urban climate also rise in importance. These include features like air pollution and increased humidity. Another unique feature of the urban climate is the phenomenon of the urban heat island. The urban heat island phenomenon was first observed over one hundred years ago in northern latitude cities, where the city centers were slightly warmer than the suburbs. (Instantaneous communications probably played a role in its identification, much as it did for other weather-related events.) For these cities, a heat island was generally a positive effect because it resulted in reduced heating requirements during the winters. It was only in the 1960s, as air conditioning and heavy reliance on automobiles grew, that the negative impacts of heat islands became apparent. The heat islands made summer conditions much less comfortable and increased air conditioning energy use. Since then the summer heat island has become the dominant environmental concern. Measurements in thousands of sites, plus the development of sophisticated dynamic simulations of urban air basins, has enabled us to better understand the relationships between urban temperatures, sunlight, and rates of formation of air pollutants. These models have also given us insights into the roles of vegetation and other characteristics of the land surface. More recently-roughly the last fifteen years-it has become possible to quantify the roles of the major features influencing the formation and persistence of urban heat islands. These developments also allowed us to answer 'what if' questions, such as, 'what if surfaces were changed to be covered with more vegetation or if the albedo of the streets or the roofs was increased'? These simulations, plus measurements of the impact of actual changes, made it possible to imagine that countermeasures to urban heat islands would result in a cooler city requiring less air conditioning and other benefits. In the past five years we have seen the first generation of countermeasures to urban heat islands appear. 'Cool' roofing materials, are now available and, in California, help comply with energy efficiency requirements for buildings. In Japan, cities are giving special incentives to buildings that provide vegetation on their roofs.

• Research Organization: Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 926307
• Report Number(s): LBNL--63394; BnR: 830404000
• Country of Publication: United States
• Language: English

Related Subjects

29 ENERGY PLANNING, POLICY, AND ECONOMY
AIR CONDITIONING
AIR POLLUTION
ALBEDO
AUTOMOBILES
CLIMATES
COMMUNICATIONS
ENERGY EFFICIENCY
HEAT EXCHANGERS
HEATING
HUMIDITY
PLANTS
POLLUTANTS
ROADS
ROOFS
URBAN AREAS
air conditioning energy efficiency urban form