The author of a new study said the combination of blackouts and extreme heat “may be the deadliest climate-related event we can imagine.”
WASHINGTON — The growing risk of overlapping heat waves and power failures poses a severe threat that major American cities are not prepared for, new research suggests.
Power failures have increased by more than 60 percent since 2015, even as climate change has made heat waves worse, according to the new research published in the journal Environmental Science & Technology. Using computer models to study three large U.S. cities, the authors estimated that a combined blackout and heat wave would expose at least two-thirds of residents in those cities to heat exhaustion or heat stroke.
And although each of the cities in the study has dedicated public cooling centers for people who need relief from the heat, those centers could accommodate no more than 2 percent of a given city’s population, the authors found, leaving an overwhelming majority of residents in danger.
“A widespread blackout during an intense heat wave may be the deadliest climate-related event we can imagine,” said Brian Stone Jr., a professor at the School of City & Regional Planning at Georgia Institute of Technology and the lead author of the study. Yet such a scenario is “increasingly likely,” he said.
The findings come just months after a winter storm knocked out power for millions of people in Texas, causing more than 150 deathsand demonstrating how easily severe weather can overwhelm electrical grids and other infrastructure.
But as much as winter storms and extreme cold remain a threat, the greater risk to human health as temperatures rise is from extreme heat.
Heat is already the most dangerous type of severe-weather event, by one estimate killing some 12,000 Americans each year. And climate change is making heat waves more frequent and severe.
The changing climate also seems to be making power failures more common. From 2015 to 2020, the number of blackouts annually in the United States doubled, Dr. Stone said. And those blackouts were more likely to occur during the summer, suggesting they were being driven in part by high temperatures, which increase demand on the electrical grid as people turn up their air-conditioners.
Because both heat waves and blackouts are becoming more frequent, “the probability of a concurrent heat wave and blackout event is very likely rising as well,” Dr. Stone said.
So Dr. Stone, along with a team of eight other researchers — from Georgia Tech, Arizona State, the University of Michigan and the University of Guelph in Ontario, Canada — set out to gauge the human health consequences when power failures coincide with heat waves.
To do that, they picked three big cities — Atlanta, Detroit and Phoenix — and looked at recorded temperatures during some of their most severe heat waves.
Next, they used computers to model the temperatures in different neighborhoods if those heat waves were to hit at the same time that a citywide blackout disabled air-conditioners.
Crucially, the researchers wanted to know how hot the insides of homes would get under those conditions — something that Dr. Stone said had never been tried before. They collected data showing the building characteristics for every single residential structure in each city — for example, building age, construction material, level of insulation and number of floors.
The results were alarming. In Atlanta, more than 350,000 people, or about 70 percent of residents, would be exposed to indoor temperatures equal to or greater than 32 degrees Celsius (89.6 degrees Fahrenheit), the level at which the National Weather Service’s heat classification index says heat exhaustion and heat stroke are possible.
