Major storms such as Hurricane Helene, which obliterated towns and turned roads into rivers after surging inland from Florida last week, have a far longer and more devastating impact upon lives than previously thought, contributing to thousands of deaths up to 15 years after they have swept through, a new study has found.
In terms of lives lost, hurricanes are generally thought to be short, sharp events. More than 150 people are thought to have died across five states after Helene tore across the southern US as a category 4 storm, with fatalities caused by rising floodwaters, car crashes or falling trees and debris.
But new research has found that big storms have an impact upon mortality that lingers much longer – for up to 15 years, ultimately causing far more deaths than first apparent. Each tropical cyclone hitting the US causes an average 7,000 to 11,000 excess deaths in total, it calculates, a death toll so vast that as much as 5% of all deaths along the eastern coast of the US since the 1930s have been the result of such storms.
“We looked at the data months and then years after a storm and we were very surprised to see that people kept on dying,” said Solomon Hsiang, a climate and public policy expert at Stanford University who co-authored the research with Rachel Young, a scientist at Berkeley.
“There is lot longer shadow than anybody expected. The impact of storms upon society is so much bigger than we realized, it’s more of a public health issue than anyone really thought before.”
The study, published on Wednesday in the Nature journal, analyzed Centers for Disease Control and Prevention data for states hit by hurricanes between 1930 and 2015. The researchers were able to calculate “pre-storm” norms for states and then track the death totals once a hurricane hit, with the echo of these storms often overlapping with the next big storm event.
What they found, according to Hsiang, was surprising – rather than a single spike in deaths from high winds and floodwater, hurricanes cause a persistent trickle of deaths for years afterwards. Certain groups suffer relatively high risks of post-hurricane deaths, the research found, such as infants and the Black population.
“When people are hit with the same amount of environmental shock, the outcomes are different for different groups which we can now see very clearly in the data,” said Hsiang.
“We have this view of storms as something we muscle through and then shake off afterwards, but what we haven’t fully realized is that once the storm has gone the impacts reverberate through communities for years. They need services, help and support that they are not getting currently.”
The new study does not provide a definitive answer as to the exact cause of these extra deaths but comes up with potential factors, such as the fallout from resulting economic and job losses after storms, suddenly overstretched local government budgets that underfund health providers, the release of environmental toxins as storms hit industrialized areas and the unhealthy impact of stress upon those who have to endure hurricanes.
“All of these feel plausible and people might be affected by a combination of them,” said Hsiang. “If we can figure out what is happening on the ground, we can design interventions and policies to eliminate this scourge of death.”
The finding that hurricanes can cause deaths 15 years after their winds dissipate “will prove controversial and will be followed up by many other studies of long-term mortality from natural disasters, said Kerry Emanuel, a scientist who specializes in hurricanes at the Massachusetts Institute of Technology and was not involved in the new paper.
But Emanuel said that he found the results of the study “persuasive, given how well the model explains the excess deaths” and that the thousands of extra deaths per hurricane were “truly astounding”.
“If they stand the test of time, these conclusions imply that climate change effects on natural hazards like hurricanes are far more debilitating than we have heretofore estimated,” he added.
The burden of extra deaths is likely to mount further as hurricane-prone states such as Florida see their populations grow while the world continues to heat up due to the burning of fossil fuels. Scientists have found that hurricanes are, on average, becoming stronger and intensifying more rapidly due to the warming atmosphere and oceans.
The climate crisis probably had a turbocharging effect upon Hurricane Helene, with the storm gathering pace over an unusually hot Gulf of Mexico. “This storm took a while to develop, but once it did it intensified very rapidly – and that’s because of the warm waters in the Gulf that’s creating more storms that are reaching this major category level,” said Deanne Criswell, administrator of the Federal Emergency Management Agency (Fema).
“In the past, damage from hurricanes was primarily wind damage, but now we’re seeing so much more water damage and that is a result of the warm waters, which is a result of climate change.”
