Urban Tree and Shade Masterplan emerges to combat Phoenix urban heat island

A view of the urban sprawl that has developed into the city of Phoenix. (Special to the Independent/Samantha Morse)

Downtown Phoenix dominates the desert skyline, but this concrete jungle is turning up the heat, literally.

The Arizona State Climatology Department says the vast amounts of concrete and asphalt in the city absorb heat much deeper than desert sand would — so the city stays hotter for longer.

“The record nighttime temperature is actually 96 degrees. So you wake up at dawn and it’s already 96 degrees. Well, it’s just going to get hotter.” Nancy Selover, the Arizona State Climatologist said.

According to a year-long study conducted by ELSEVIER, an independent information and analytics company, neighborhoods with some level of shading saw temperature drops up to 16 degrees compared to neighborhoods with minimal or no shading.

These temperature differences made dramatic impacts, according to ELSEVIER, during the 2003 heat wave.

Already existing shade among the buildings in downtown Phoenix. (Special to the Independent/Samantha Morse)

“We found significant 2003 summertime temperature variations among Phoenix neighborhoods. Simulated estimates of exposure to heat stress showed that the warmer neighborhoods more often exceeded the ‘danger’ threshold in summer 2003.” ELSEVIER said in their 2003 research paper.

The danger threshold is determined to be within 104 and 130 degrees Fahrenheit.

But the city of Phoenix has several solutions that could help reduce the heat, including the Urban Tree and Shade Masterplan, which will be implemented over the next 30 years.

The masterplan aims to make Phoenix the nation’s first “heat ready city” said Phoenix Chief Sustainability Officer Mark Hartman.

The plan aims to double the current tree canopy and structured shade all around metro Phoenix over the next decade, to provide cooler areas where people can go to seek relief both everyday and in an emergency, according to Mr. Hartman.

“It’s a problem for the human body. Over the course of a 24-hour period, you need some release, and some relief from that heat.” Ms. Selover said.

Naturally, a desert’s soil doesn’t absorb heat very deeply; only on the surface level. Once the sun sets, this heat dissipates very quickly, according to Ms. Selover.  In contrast, concrete absorbs the heat on a deeper level, and it takes much longer to dissipate throughout the night, effectively raising the minimum and nighttime temperatures.

According to the Arizona State Climatology Office, the minimum recorded temperature has risen 9.4 degrees since 1991. Whereas from 1901 to 1940, the average minimum temperature rose less than 1 degree.

This phenomenon is known as an “urban heat island.”

These continuous heat levels are a real and tangible problem for many Phoenix residents without access to air conditioning such as low-income households and the homeless.

“I can’t hardly sleep some nights it’s too hot.” Pete Bodin, a local homeless man said. “And, it’s not like I can go sleep inside. They won’t let me.”

By providing more shade, the amount of direct sunlight heating up the concrete will be cut down dramatically, thus keeping them from absorbing the heat in the first place, according to Ms. Selover.

Along with increased shading, the city of Phoenix also aims to repave up to 80 percent of asphalt in the area with less heat absorbent materials by 2050.

The few trees that have been planted are still in infancy, officials say.

“We can’t exactly plant trees with a 30-foot canopy.” Ms. Selover said.

Because of the slow rate at which trees grow, the project will take years to fully implement. However, trees can’t thrive in many of the more urban areas of Phoenix, including downtown.

In order to combat this, the city of Phoenix, as well as many businesses, have installed structured shading to provide patios or rest areas for employees and patrons.

These structures include transit stations such as Light Rail and bus stops.

The city of Phoenix Arts and Culture Commission approved three new transit stop designs for metro Phoenix in September, which aim to fuse functionality with artistry. Local artist Maria Salenger was commissioned to design the new stops with a retro theme that increases shade and seating for waiting passengers.

Editor’s note: Ms. Morse is a journalism student at Arizona State University

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