Hurricane Helene ripped up from Florida to the Carolinas last week, killing more than 100 people and leaving devastation in its wake that will take weeks or months even to assess.
A new study published in Nature suggests its impacts will be even greater. On average over the past nearly 100 years, a tropical cyclone hitting the U.S. is associated with somewhere between 7,000 to 11,000 deaths. Helene, though, was more powerful than the average; its likelihood and rainfall intensity were increased by human-caused climate change.
When storms are active, people die, for instance, when floods rip through neighborhoods, or when trees fall on them. But the new study shows that losses continue for months, and can last as long as 15 years, after the storm passes taxing people’s health and economic well-being, contributing to thousands of premature deaths. The total impact, the study suggests, adds up to more than 3.5 million people since 1930, more than the total number of deaths from motor vehicle accidents over the same period of time and as much as 5% of the U.S.’s total deaths.
The analysis underscores that “tropical cyclones and hurricanes are a much greater public health burden than we previously thought,” says Rachel Young, an environmental economist at the University of California, Berkeley and author of the paper.
The National Oceanic and Atmospheric Administration, or NOAA, counts the number of deaths directly attributed to hurricanes and tropical cyclones each year: out of the 501 storms that the study looked at, the official numbers say an average of 24 people die after each storm. But the new analysis suggests the toll is some 300 times higher than the official numbers.
It makes clear, Young says, that “we should be rethinking how we are responding and the kinds of programs and policies we’re putting into place after these events,”— like in the wake of Helene, a storm that is already far outside the average. The official count has already exceeded 130 people, and the number is climbing.
Uncovering the true toll
The new accounting fits with other recent analyses that suggest the true impact of climate-worsened disasters, from hurricanes to heat waves to wildfires, is orders of magnitude larger than the federal government reports. If these larger estimates are taken into account, the human and economic costs of human-driven climate change balloon, suggesting a problem that is much larger than most federal officials acknowledge.
This study, and others like it, “cast in sharp relief” the climate impacts on human life in the U.S., says Robbie Parks, an environmental health expert at Columbia University. He led a previous study that found an estimated 18,000 uncounted deaths in the months following hurricane landfalls from 1988 to 2019.
The new analysis traces out the even-longer term ripples. The researchers looked at tropical cyclones that made landfall in the U.S. between 1930 and 2018. They gathered data on all deaths in the country for that same time period, and looked at the changes in deaths reported in counties before and a full 20 years after a serious storm hit. They accounted for some counties that were hit by another storm while the impacts of the first were still playing out. Researchers also looked at other factors that changed over time, like changes in population, or the time of year.
The magnitude of the impacts surprised even the researchers. “We spent many, many years trying to make sure that what we were measuring wasn’t some sort of anomaly in the data, wasn’t some kind of fluke, that it was really the response from these hurricanes,” says Young. “We did every kind of test you could possibly imagine. We thought about every kind of factor that could be driving these results.” But the data spoke for itself, she says.
Unexpected deaths jump quickly after a storm hits, then keep rising for six years after the impact. They don’t go back to the previous death rate until 15 years afterward.
When the researchers looked more closely, they saw that Black Americans were more than three times as likely to die in the years following the storm than white Americans.
They also found heightened risks for people over 65. But so were infants—even ones that weren’t yet in utero, or born, at the time of the storm. The study found their death rates were 16 times higher than for toddlers, teens, and adults under 65. The study didn’t identify why—but Young thinks it could be related to the long-term, emotional and economic effects on mothers, an insidious tail of pain left behind by a hurricane.
How the harms happen
The effects linger, Parks explains, because the harms linger. After a hurricane, people often have to deal with destroyed homes. They spend their savings to move, or repair, or simply survive after a disaster. Or they move away, losing support networks and leaving others behind without one. And local economies reshuffle, so people lose their jobs and deal with new economic burdens.
“Think about a place which has infrastructure, and suddenly does not—and then you have all these people living without essential infrastructure. You can imagine the slow creep of health effects occurs over time,” says Parks.
The social and economic disruption also impacts health care. Doctor and researcher Arnab Ghosh of the Weill Cornell Medical College of Cornell University treated patients in Puerto Rico after Hurricane Maria in 2017 and in New York City after Hurricane Sandy in 2012. His patients struggled with the fallout for years.
“There is this rippling effect throughout the fabric of society after these events happen,” Ghosh says. “This is where the social gradients, the fault lines that exist in our society, play a role.”
After storms, diabetic patients suffer from interrupted insulin supply. Others can’t access dialysis, or move far from their care teams, losing crucial continuity. Some deal with mental health issues worsened by storm-related fallout; others find their cardiovascular problems exacerbated by stress or poor living conditions.
Many of the problems, Ghosh says, were not easily traced directly back to the storm, without careful probing and recording by doctors and nurses. It was often even difficult for a patient to see or understand the connection, he says. So Ghosh sees exactly how the direct count of health problems and even deaths related to the hurricane could—easily—be underestimated.
And, Ghosh says, it’s a critical context for medical professionals like him to consider as they treat patients after the disasters—to know that they need to keep looking for connections to the storm, for months and years after.
Now we know. What next?
After Hurricane Maria hit, the Puerto Rican government initially estimated the death toll of the storm at 64. Puerto Ricans insisted that was a gross underestimate. Further analyses would put the number of lives lost in the thousands.
Roberto Rivera, a statistician at the University of Puerto Rico, Mayagüez, knows the impact of a hurricane can persist. “I’m still in Puerto Rico and all you have to do is drive around a little bit and you see the light poles, all tilted,” he says—and if the infrastructure is still in flux, so must be people’s lives and health.
An accurate count, Rivera says, is fodder to say to government leaders “look, we need to enhance the emergency policy. There are people who are dying unnecessarily.” But he says, the statistical assessments stretching out so many years are challenging, and the uncertainty in the estimate ranges in this new analysis are too high.
Helene was a more intense storm than most Climate change intensified its destructive rainfall, adding an extra 50% to the rain that fell in Georgia, NC, and beyond. Scientists expect hurricanes to continue intensifying rapidly and carrying more rainfall island as the planet heats up further.
The full picture of Helene’s damage will not be filled in for years, says Young. But whatever the official statistics say, she says, the true impact is almost certainly higher.
“We need to be giving people a lot of attention even months and years after, making sure that they’re getting their insurance payouts on time, making sure that they’re being made whole and that they can recover and they’re not being forgotten about just because the hurricane was a month ago,” Young says.