How city design creates an urban heat island
Rising temperatures have killed hundreds of people each year and the layout of the City of Phoenix has made that heat more dangerous.
155 people died of heat related illness in 2017 throughout the city as temperatures rise according to the Arizona Department of Health Services.
Researchers identified the phenomenon, the “Urban Heat Island” effect, as a cause of increasing deaths due to heat exposure.
Dr. Jennifer Vanos, Senior Sustainability Scientist at Arizona State University, explained the effect.
“The Urban Heat Island effect means that the air temperatures, in an urban area, are higher than temperatures in a rural area,” Vanos said.
The higher urban temperatures are due to how urban building materials, such as concrete and asphalt, absorb the heat from the sun during the day and remain warm throughout the night.
Paulette Fernandez, local resident, explained how the heat affects her daily life.
“I order groceries and pay $8 for delivery so I don’t have to walk a block and back with a bunch of bags in 110 degree heat,” Fernandez said.
Heat islands exist in every major city around the world, from Phoenix to Toronto. For colder cities they are beneficial, while in hot cities they can be dangerous.
“You can have a heat island in Minneapolis in January where it’s 10 degrees Fahrenheit warmer in the urban area than in the rural area, but it’s still only 20 degrees,” Vanos said. “In Phoenix, same deal, but we are concerned about our heat islands when Downtown Phoenix is 115 and the outskirts of the city are only 105.”
According to Vanos, outside of heat exposure deaths the biggest threat extreme heat islands pose to Phoenix is to residents ability to grow things such as vegetation and food in the city.
“With higher temperatures, you have higher evaporation from the surface and you’re losing water to the air rather than it going to the vegetation and soil,” Vanos said.
Another threat the city may face with extreme heat is a mass migration of residents leaving the city either for the suburbs or for other cities.
“If I could magically teleport my friends, family and source of income to a better place, I would,” Fernandez said. “I have no plans to stay more than a few years to finish school and find a bearable place year-round that has what I need.”
Vanos said that there are multiple ways in which cities and individuals can make lessen the effects of the heat island in Phoenix.
“If there’s a way to limit our air conditioning usage it’s not just going to save you money, it’s going to reduce the amount of heat that’s being released into the urban atmosphere,” Vanos said.
Businesses must also lessen their air conditioning usage.
“We don’t need to air condition spaces overnight to 70 degrees when they’re not used, same thing in houses when we’re not home,” Vanos said.
In order to combat the heat island, Phoenix should focus on creating “cool islands,” areas within a city where temperatures are cooler than the average of the city, Vanos said. These cool islands may be created by shade and vegetation in a certain area.
The City of Phoenix began a plan to plant thousands of trees and other vegetation throughout the city, in order to provide canopy coverage for 25 percent of the city.
Stacey Champion, spokeswoman for the advocacy group Rogue Green, commented on the city’s lack of progress with their plan.
“I think it’s a combination of lack of vision and leadership, not making it a real priority, and being too beholden to the development community versus doing what is necessary for the greater good of our community,” Champion said.
According to Vanos, cities could also paint rooftops white, rather than black or other dark colors, which would reflect the sun’s energy instead of absorbing it. This could have been accomplished with green roofs, where a rooftop is covered with vegetation, so the sunlight is used by the plants and not heating the building.
Vanos made clear that the heat islands are not caused by climate change. Desert cities are dangerous throughout the summer anyway, therefore cities must make efforts to protect people, even if they do not believe in climate change.
“Even if the climate were to stop warming, we’re still going to have heat deaths,” Vanos said.