May 24, 2023 - Climate

Heat wave and black out would hospitalize half of Phoenix residents

Illustration of a skull and crossbones sun in the sky

Illustration: Sarah Grillo/Axios

Half of Phoenix residents would need emergency medical attention if a multiday blackout were to coincide with a heat wave, a new study revealed.

Why it matters: Heat waves are deadly even when people have access to air conditioning. Combine extreme temperatures with a blackout and the heat-related death rate would spike by 700%, according to the report published this month in Environmental Science & Technology.

State of play: U.S. electrical grid failures increased 150% between 2016 and 2021, and most often occurred during the summer, when elevated electricity demand collides with heat, wildfires and storms, the study authors found.

What they did: Researchers modeled how today's population and infrastructure would tolerate a heat wave like the one Phoenix experienced in 2006 — when afternoon temperatures averaged 113 degrees for five straight days — and an electrical blackout happened simultaneously.

What they found: It may seem counterintuitive, but Phoenix residents aren't well-equipped to handle prolonged, extreme heat because of our reliance on air-conditioning, lead author Brian Stone Jr. tells us. He's an environmental planning professor at Georgia Institute of Technology.

  • The tremendous temperature swing we'd experience from our air-conditioned normal in the 70s to an extreme of 113 would stress our bodies in a way that could lead to heat illness or worse, he said.

Threat level: Stone said it's important to recognize that the sobering death and hospitalization estimates in the study are not based on future anticipated impacts of global warming — they're grounded in today's climate reality.

Zoom in: Between cyberattacks and worsening storms, it's impossible to fully defend our electrical grids. That's why Stone encourages cities to invest in measures to reduce heat instead of focusing solely on grid resiliency.

  • The study found that increasing the tree shading to 50% of all streets would reduce heat mortality by 27% in Phoenix.
  • Installing "cool roofs" that reflect sunlight on all buildings would bring down deaths by 66%.

What's happening: A Tree and Shade Master Plan adopted by the Phoenix City Council in 2010 calls for a 25% tree canopy throughout the city by 2030. City staff told Cronkite News last month it's reached only about 12%.

  • Los Angeles requires buildings to have heat-reducing roofs, something Stone says Phoenix should immediately consider.

Between the lines: ASU professor and co-author Matei Georgescu tells us Phoenix and the university are actively testing new ways to mitigate heat, including "cool pavements" and "green rooftops."

  • He says the Valley should also enhance its backup plans, like mass generators, to provide immediate relief should a blackout/heat wave combination strike.

Climate reporter Andrew Freedman's thought bubble: "With climate change already leading to more frequent, intense and long-lasting heat waves around the country and worldwide, the grid is likely to be tested in new ways that it was not designed for."


Get more local stories in your inbox with Axios Phoenix.


Support local journalism by becoming a member.

Learn more

More Phoenix stories

No stories could be found


Get a free daily digest of the most important news in your backyard with Axios Phoenix.


Support local journalism by becoming a member.

Learn more