Urban 'heat island' effect is only a small contributor to global warming, and white roofs don't help [View All]

Stanford Report, October 19, 2011

Urban 'heat island' effect is only a small contributor to global warming, and white roofs don't help to solve the problem, say Stanford researchers

Heat emanating from cities – called the "urban heat island" effect – is not a significant contributor to global warming, Stanford researchers have found. They also concluded that if all the roofs in urban areas were painted white, it would increase, not decrease, global warming.

BY LOUIS BERGERON

Cities release more heat to the atmosphere than the rural vegetated areas around them, but how much influence these urban "heat islands" have on global warming has been a matter of debate. Now a study by Stanford researchers has quantified the contribution of the heat islands for the first time, showing that it is modest compared with what greenhouse gases contribute to global warming.

"Between 2 and 4 percent of the gross global warming since the Industrial Revolution may be due to urban heat islands," said Mark Z. Jacobson, a professor of civil and environmental engineering who led the study. He and graduate student John Ten Hoeve compare this with the greenhouse gas contribution to gross warming of about 79 percent and the black carbon contribution of about 18 percent.

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Jacobson and Ten Hoeve are authors of a paper describing the research that will be published in Journal of Climate. The paper is available online http://www.stanford.edu/group/efmh/jacobson/Articles/Others/HeatIsland+WhiteRfs0911.pdf">now. The study modeled climate response from 2005 to 2025.

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