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 deaths and
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.
In Detroit, more than 450,000, or about 68 percent, would be
exposed to that indoor temperature. In Phoenix, where a vast majority of
residents rely on air-conditioning, the entire population would be at risk —
almost 1.7 million people.
Even without a blackout, some residents in each city lack
access to air-conditioning, exposing those residents to dangerous indoor
temperatures during a heat wave. Those numbers range from 1,000 people in
Phoenix to 50,000 in Detroit, based on the characteristics of their homes, the
authors found.
That exposure is most pronounced for the lowest-income
households, who are 20 percent less likely to have central air-conditioning
than the highest-income households.
The authors reported that each city had designated public
cooling centers for extreme heat. But they found that in each case, those
centers could accommodate just 1 percent to 2 percent of the total population.
And none of the three cities requires those cooling centers
to have backup power generators to run air-conditioners in case of power
failures.
“Based on our findings, a concurrent heat wave and blackout
event would require a far more extensive network of emergency cooling centers
than is presently established in each city, with mandated backup power
generation,” the authors wrote.
The New York Times asked officials in Atlanta, Detroit and
Phoenix to comment on the paper’s findings, and to describe their plans for
responding to a combined blackout and heat wave.
A spokeswoman for the city of Phoenix, Tamra Ingersoll, said
that in a crisis situation like a heat wave overlapping with an extended power
failure, many residents would leave the city on their own. Emergency response
for those who remained would focus on “vulnerable populations such as the
elderly, infirm or low-income individuals,” she said.
Christopher Kopicko, a spokesman for the Detroit Office of
Homeland Security & Emergency Management, said that only one of the city’s
11 cooling centers had a backup generator. But he said Detroit had recently
bought mobile generators that could be sent to cooling centers that needed them
and that residents could go to any of the city’s 12 police precincts, which
have backup generators. He also said some of the city’s largest venues had
agreed to act as mass shelter sites.
The office of the Atlanta mayor, Keisha Lance Bottoms, did
not comment.
The Federal Emergency Management Agency, in response to
questions about whether it had plans for helping a large city deal with a
combined blackout and heat wave, pointed to a 2017 plan for managing the
effects of a long-term power failure.
But that document did not address how the agency would
respond if a heat wave struck during such a blackout, beyond noting that “lack
of power will create challenges to providing consistent heat or air
conditioning and sufficient sanitation/hygiene in shelter or other mass care
facilities.”
Other cities across the United States are at risk of facing
similar health threats from a combined heat wave and blackout, in terms of the
share of their population that could very likely be in danger, the authors
found.
“We find that millions are at risk,” Dr. Stone said. “Not
years in the future, but this summer.”
