Can smartphones be a tool to learn about urban heat islands?


Barbara Trapido-Lurie

Modern cell phones automatically track their battery temperatures – providing a data source with potential as vast as the number of cell phone users. Cell phone batteries become warmer when the phones are used heavily, when the phone is stored in a warm location, like a shirt pocket, or when it’s warm outside.

By looking at data from large numbers of phones, is it possible to tease out the impact of air temperature and obtain a rich source of information about how outdoor temperature varies over the course of a day and in different settings?

An international team of researchers looked into this question – and found that when temperatures of large numbers of cell phones are analyzed, average battery temperature correlates strongly with air temperature.

These findings, published in Geophysical Research Letters, are of potential interest to climate scientists Matei Georgescu and David Hondula of ASU. Inside Science , a science news service, asked both for their perspectives on the research.

"It's a very innovative way to look within urban areas," responded Georgescu, who researches the environmental impacts of urbanization. He pointed out that the smartphone estimates could complement other more accurate but less ubiquitous data sources, such as satellites. "Satellite overpasses don't occur every minute," he explained. "With smartphones, you basically have real-time information."

David Hondula, whose research focuses on health informatics, climate and health, had a different take: He proposed that smartphone temperature data could potentially give personalized feedback on dangerous heat exposure. "If your phone is tracking your weather conditions, you might have a personalized alert that you have experienced excessive heat as you've moved through your daily life," said Hondula.

The original research was conducted by collaborators at Wageningen University in the Netherlands, James Robinson of OpenSignal and the Massachusetts Institute of Technology. Inside Science contacted Georgescu and Hondula as impartial commentators, not directly involved with the published research.

Matei Georgescu is an assistant professor in ASU’s School of Geographical Sciences and Urban Planning, an academic unit in the College of Liberal Arts and Sciences, and a senior sustainability scientist with ASU’s Global Institute of Sustainability. David Hondula is a postdoctoral researcher with the Center for Policy Informatics, a research unit in the College of Public Programs.