Mitigating the warming of urban expansion: Geography matters

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:

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Photo courtesy Ken Fagan, Arizona State University