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As urban areas expand, they become warmer. Scientists have demonstrated that it’s possible to mitigate this effect in various ways – with the most-widely-researched adaptive technologies being cool roofs (painted white) and green roofs (covered with vegetation).
A team of researchers, led by Matei Georgescu, assistant professor of geography, is taking a closer look at the impact of these mitigation strategies. In a study just published in theProceedings of the National Academy of Sciences, the researchers explain their findings: While adaptive technologies can counteract urban warming, their impact varies, depending on the local climate and on the season, and can have unintended negative consequences.
“This is the first time all of these approaches have been examined across various climates and geographies,” said Georgescu. “We looked at each adaptation strategy and their impacts across all seasons, and we quantified consequences that extend to hydrology (rainfall), climate and energy. We found geography matters,” he said.
For example, widespread use of roofs painted white has been shown to mitigate summertime temperatures. However, in northern locations, this strategy continues to cool buildings in the winter – requiring more energy to keep the buildings at a comfortable temperature. In the southwest US and in Florida, the white roofs produce a desirable cooling effect in the summer, but also have a negative effect on rainfall – not so desirable.
This research was supported by the National Science Foundation under a Water Sustainability and Climate grant with Georgescu as principal investigator.
The paper's co-authors, Philip Morefield, Britta Bierwagen and Christopher Weaver are affiliated with the US Environmental Protection Agency.
To read more about the research, see:
Selected additional news media coverage of this research:
Built environment leads to heating, Australian Broadcasting Corporation's Radio National, March 1, 2014
Is white--or green--the new black in cities?, National Science Foundation Discovery, March 11, 2014
Research examines effects of cool roofs, Civil Engineering, March 11, 2014
Green and cool roofs could eliminate the urban heat island effect, Science for Environment Policy, European Commission DG Environment News Alert Service, March 28 2014
On a Cool Roof: City Planners, Activists and Researchers Debate Climate Change, Next City, May 28, 2014
Interview with Matei Georgescu on The Science Show,Science360 News Service, July 7, 2014
Glass Paint: Secret to Keeping Metal Roofs Cool on Sunny Days, National Geographic, August 16, 2015
How cities can beat the heat, Nature News & Commentary, August 26, 2015
Photo courtesy Ken Fagan, Arizona State University