A new study suggests that white and green rooftops in urban areas can help reduce the buildup of heat in cities known as the heat island effect.
The color white reflects a large portion of sunlight and therefore reduces heat, and planted green rooftops may actually reverse the influence of global warming.
"What we found for cool, green, and hybrid roofs is that they don't just offset urban expansion-they can offset additional warming," says lead study author Matei Georgescu, assistant professor in the school of geographical sciences and urban planning, and senior sustainability scientist at Arizona State University's Global Institute of Sustainability.
Having been pushed by the federal government recently, green rooftops were not well researched until now, but the results are clear according to the scientists.
"Each can completely offset the warming due to urban expansion and can even offset the warming due to greenhouse gas emissions," said Georgescu.
Other scientists concur with the published research.
"The study is a step in the right direction and is consistent with other studies that suggest that cool roofs can offset localized urban heat island impacts," said Mark Jacobson, an environmental engineering professor at Stanford University.
"This is a really important study because it shows how designing better urban systems (especially by changing rooftops) can help keep our cities cool as they grow (and otherwise have a stronger 'urban heat island') and as global warming becomes more and more serious over time. While this has been considered for individual cities before, this study is really the first comprehensive look at how changing city rooftops could have widespread, positive impacts on climate across large metropolitan regions in the country," said Jonathan Foley, director of the Institute on the Environment at the University of Minnesota in an email to Popular Mechanics.
The heat island effect is brought about in large cities because of the significant amount of black colored surfaces in them. From rooftops to roads, there is little to reflect heat, and most of it is absorbed, and re-radiated out at night, keeping cities warmer than their surrounding environments.
"Our work shows that geography matters," Georgescu said.
