Phoenix is a successful, growing city but it?s getting far too hot. Residents experience temperatures like 100 degrees F at 10:30 a.m. and they?re looking for a way to cool off. Phoenix wasn?t always this hot. In 1949, the average temperature for July was 90.4 degrees. Last year’s average temperature for July was 94.2 degrees.
Climate experts say the area is an “urban heat island,” where the combination of sun, tile roofs, unshaded streets and lots of asphalt keeps things hot day and night. It stays hotter longer in Phoenix than in most places. Since 1949, the average low temperature at Phoenix Sky Harbor International Airport has risen more than 10 degrees. And over the past 40 years, the number of hours a day when the temperature has reached over 100 degrees has jumped dramatically.
Most desert areas compensate for daytime heat by cooling off radically at night. The Sahara temperature drops as much as 50 degrees after sundown, but the Sonoran Desert around Phoenix doesn’t. The question residents ask is: why not?
It’s partly due to different soil composition. The desert sands of the Sahara retain heat at a lower rate than the hard surface of the Sonoran Desert. But most of all, no one has paved over the sand of the Sarhara to create parking lots.
Nearby Tucson isn?t as hot as Phoenix. The daytime high in Phoenix averages 4.5 degrees higher than in Tucson, and the nighttime low was more than 10 degrees warmer. This could partly be because Tucson has a higher altitude and more wind, but it?s more likely because Tucson has a lot less pavement than Phoenix.
Phoenix is making plans to cool down and become more livable. Some possible changes are the use of lighter-colored pavement and roofs that reflect, rather than absorb, energy. Some of these changes will go into the city?s building code.
Other cities are also trying to beat the heat. Tucson instituted reflective-roof standards for newly built city buildings after an experimental building with a reflective roof saved 4% in energy costs. Atlanta paved some of its many parking lots with porous material that absorbs and releases heat more efficiently than standard asphalt. Even Chicago has started a program of putting gardens on rooftops. Salt Lake City has been testing new rooftop materials since 1995.
Some parts of Phoenix are cooler than others. Satellite imagery shows that at 11 a.m., the Arcadia neighborhood, with orchard trees and its big grassy lots, can be up to 10 degrees cooler than other areas. The Fort McDowell Indian Reservation, which is east of Scottsdale, cools down more rapidly than Scottsdale, because it has little development.
Rapid development has caused a lot of the heat increase, as farm land is converted into suburbs. “As the city grows and expands outward, the heat island expands with it,” says Nancy Selover, the state’s assistant climatologist.
Older neighborhoods are cooler because they have bigger yards and larger trees. Brent Hedquist is a college student who recently drove around the area trying to understand the way the heat works. He says, “As you drive along the interstate, it’s mostly asphalt, lots of cars. In some places, it’s almost an urban canyon where all the heat gets trapped and rises up.” He noticed that it was hotter in the new housing developments, with their dark, red-tiled roofs, stucco walls and small yards.
“Out there in the new development, I saw just a bunch of homes very close together,” Hedquist says. “A lot of the older neighborhoods I drove through which had larger yards were cooler.”
Those of us who want to beat the heat need to learn from the neighborhoods of the past and insist on heat reflective building materials and lots of trees.
Learn practical suggestions for cooling things down from ?The Coming Global Superstorm? by Art Bell & Whitley Strieber, now only $9.95 for a hardcover signed by Whitley,click here.
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