Heat Wave and Blackout Would Send Half of Phoenix to ER, Study Says

If a multiday blackout in Phoenix coincided with a heat wave, nearly half the population would require emergency department care for heat stroke or other heat-related illnesses, a new study suggests.

While Phoenix was the most extreme example, the study warned that other cities are also at risk. Since 2015, the number of major blackouts nationwide has more than doubled. At the same time, climate change is helping make heat waves worse and increasing instances of extreme weather around the world.

The study, published Tuesday in the journal Environmental Science and Technology, suggests that the risk to cities would be compounded if a hurricane, cyberattack or windstorm were to knock out power during a heat wave and deprive thousands of air conditioning.

This summer, two-thirds of North America, including the Southwest, could experience shortfalls in the electrical grid, particularly during periods of extreme heat when demand for air conditioning spikes, straining resources, according to an analysis released this month.

The new analysis found that Phoenix, which is heavily reliant on air conditioning to keep residents cool in the desert heat, would experience immense loss of life and illness if a citywide blackout during a heat wave lasted for two days, with power gradually restored over the next three days.

Under that scenario, an estimated 789,600 people would require emergency department care for heat-related illnesses, overwhelming the city’s hospital system, which has only 3,000 emergency department beds, the study said. An estimated 12,800 people in Phoenix would die, the study said.

To anticipate the effects of a prolonged loss of power during extreme heat, researchers modeled the temperatures that residents in Atlanta, Detroit and Phoenix would be exposed to on an hourly basis, if the power were on during a heat wave, and if it was not.

In Atlanta, 11,600 people, or about 3% of the population, would require emergency department care if a five-day heat wave coincided with a multiday blackout, the team found. The scientists estimated that six people in Atlanta would die during the dual crises. The team found that 216 people would die during a heat wave and power failure in Detroit.

The researchers acknowledged certain limitations in their findings. For example, their model assumed that people would stay put during a heat wave and blackout; in reality, some people would be able to relocate to cooling centers.

This article originally appeared in The New York Times .