Extreme heat could be with us for years The Mesa Tribune | The Hometown Newspaper for the city of Mesa, AZ

Extreme heat could be with us for years

Extreme heat could be with us for years

By Danya Gainor
Cronkite News

Arizona will experience more days of extreme heat in the coming decade, according to an Arizona State University study.

But researchers are looking for ways to mitigate a hotter, drier climate.

The study, “The Motley Drivers Of Heat And Cold Exposure In 21st Century U.S. Cities,” is one of the first looks at human exposure to extreme temperatures, examining three factors that haven’t previously been considered together: data on population growth, greenhouse gas emissions and temperature changes caused by human development.

Researchers at ASU’s School of Geographical Sciences & Urban Planning ran decade-length climate simulations “to quantify potential changes in population-weighted heat and cold exposure” in metropolitan regions.

Phoenix and other fast-growing Sunbelt cities will see the “largest relative changes in population heat exposure,” according to the paper.

“It was all about trying to understand how these three major factors combined and interact to determine better how humans will experience climate change in the future,” said Ashley Broadbent, an assistant research professor at the School of Geographical Sciences & Urban Planning who co-authored the study.

“We need a local-to-regional scale of information to try to quantify the different agents (variables), these different agents are responsible for impacting climate change,” said Matei Georgescu, a co-author of the study and associate director of the ASU school.

Every city has its definition of extreme heat – in Phoenix, it’s 112 degrees. According to Austin Jamison, a meteorologist at the National Weather Service in Phoenix, August and July were the two hottest months recorded in Phoenix since official record keeping began in 1896.

September 2020 tied with September 2010 as the third hottest September on record in Phoenix, he said.

“The way the weather pattern played out this summer,” Jamison said, “we have a lack of clouds and humidity, which would otherwise reduce the amount of solar energy to bake the ground. And there were less thunderstorms around that normally help cool the air as well. These patterns could very well happen each year.”

Based on data provided by the Climate Prediction Center, Jamison also predicts this winter will be warmer than usual in Arizona.

“If you look at the predicted forecast for these next few months, we expect a 50 percent likelihood that temperatures will be above normal,” he said. “We are looking at a possibility of below-average precipitation, too.” The team is focused on the smaller-scale impacts of their research.

“If we are discussing extreme heat,” Georgescu said, “what we are really very interested in is not the extreme temperature itself, but the extreme impact it will have on humans.”

Maricopa County recorded 197 heat-related deaths in 2019, compared with 182 the previous year.

The public’s vulnerability to climate change must be addressed “on multiple levels,” Broadbent said, “mainly through infrastructure, but also through some of the measures that will help protect vulnerable people from heat. We have quite a lot of projected population growth for the Phoenix metropolitan region, so that really compounds another potential problem to heat deaths.”

The increasing heat over the next few years will not affect Arizona residents equally, and Phoenix has projects in place to prepare for this, said Ariane Middel, a senior scientist at the Global Institute of Sustainability and Innovation at ASU.

“It’s important for the city to identify disparities and make a plan to reduce heat exposure. And they have,” she said

To help battle the increasing heat in Phoenix, the Phoenix Street Transportation Department this year chose sections of eight neighborhoods and one city park for a pilot project that involves painting pavement with a lighter color than asphalt.

Cool pavement, reflects sunlight rather than absorbs the heat.

Over the past 10 years, Phoenix has also been planting more trees and building shade structures as part of its Tree and Shade Master Plan to achieve an average of 25 percent shade coverage for the entire city.

Middel said, “If you do plant trees or do these interventions, to do them where people are. It’s not just good enough to increase the tree canopy cover in the Valley.

“It’s important to plant those trees where people actually stand at the bus stop, or where people walk so that they’re directly getting the benefits from the shade.”

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