ASU study: Urban sprawl might cause higher summer temps

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Matei Georgescu Matei Georgescu

We live in a desert and expect our summer heat.

But, how much worse can it get?

According to a new study by Arizona State University's School of Geographical and Urban Planning and its School of Mathematical and Statistical Sciences, temperatures in a large portion of our state could jump between 2 to 7 degrees in the several decades as a result of urban sprawl.

They say because we live in the fastest growing megapolitan in the United States, we could see an expansion of what we've come to know as the "Heat Island Effect."

Basically, the more concrete you have in terms of buildings and roads, the hotter it gets during the day.

And, because concrete and asphalt absorbs and then releases heat, it cools off less at night.

"Further potential urbanization can make things considerably warmer," said Matei Georgescu, the study's lead author and an assistant professor at ASU's School of Geographical Sciences and Urban Planning.

Using growth projections by the Maricopa Association of Governments for Arizona's Sun Corridor, which includes Phoenix, Prescott, Tucson and Nogales, researchers identified potential temperature increases by 2050.

"Worst-case scenario locally, we're looking at an increase during the summertime of 7 degrees," said Georgescu.

Best-case scenario with less growth, we're looking at a 2- to 3-degree increase in summer temps.

Georgescu says even if the Sun Corridor grows unchecked, maximum potential temperature increases could be cut in half by simply painting building rooftops white.

"What happens is a lot more of the incoming radiation is reflected back to space," he said.

Looking ahead, Georgescu points out there are things we can do to offset the consequences of urbanization, such as planting trees for shade.

Using porous asphalt will prevent run-off and allow monsoon rain to be absorbed and then released back into the atmosphere.

"Direct evaporation is an immediate cooling effect, he said. So, it allows for an additional way to cool the local land surface."

Georgescu stresses this is an important area of study because urbanization-induced warming can have up to three times the impact on our climate than green house gases.

"Really, what this tells you is there is tremendous opportunity for Arizona to grow sustainably and incorporate different strategies for adaptation and mitigation.

If you'd like to read more about this ASU study, it's published in the journal Nature Climate Change.

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