About 3,000 residential buildings in Albany sustained damage, and 49 were destroyed. There was also extensive crop damage in the state, as some areas saw sustained winds well above hurricane intensity, or 75 mph.
Now a new study, published Wednesday in the journal Nature, shows that storms such as Michael that extend their damaging path far inland are becoming more likely to occur as ocean temperatures increase in response to human-caused global warming.
The study, by Lin Li and Pinaki Chakraborty, scientists at the Okinawa Institute of Science and Technology, identifies trends in observed hurricane behavior among landfalling storms in the North Atlantic Basin during the 1967 to 2018 period.
They found a slower rate of hurricane decay, defined as the decrease in storm intensity during the first 24 hours after a storm makes landfall, since they’re now holding onto more moisture picked up from warmer seas. The study found that whereas hurricanes were likely to decay by 75 percent within 24 hours after moving inland, that weakening rate has now declined to 50 percent.
Or, expressed differently, whereas a storm occurring 50 years ago held onto 24 percent of its intensity after spending 24 hours over land, that has now doubled, to 48 percent.
Using computer model simulations and statistical analysis, the authors indicate that the slower decay rate, which exposes inland areas to greater wind and flood damage, is correlated with how quickly ocean temperatures are increasing. Computer model simulations of hurricanes showed that additional moisture is most likely the main cause of these trends, though slight eastward shifts in storm tracks as global warming continues plays a small role as well by keeping storms closer to their moisture source, the study found.
If these trends continue, it could make hurricanes — already the most expensive natural disaster in a typical year — even more costly.
“Storms like Michael (2018) and Ike (2008) are prime examples of notable wind damage occurring well inland from the landfall point given a slower rate of weakening than typically expected,” Steven Bowen, head of catastrophe insight at Aon, the reinsurance firm, wrote in an email. In response to the new research, Bowen said that, should it prove to be accurate, “it would certainly pose more risk from a damage and resultant loss perspective.”
During the record-breaking 2020 hurricane season so far, hurricanes Zeta and Isaias have extended their wind damage for hundreds of miles after landfall, with Zeta carving a swath of wind damage from southern Louisiana to Atlanta.
Although these findings are not yet backed up by other studies, hurricane researchers not affiliated with the new paper said it matches other recent work and raises key questions that have not yet been an area of research focus.
“This study indeed helps provide a fuller picture of how climate change is leading to increased threat from landfalling hurricanes,” Michael Mann, director of Penn State’s Earth System Science Center, who has published studies on how human-caused global warming is altering hurricanes, said in an email. “The fuller picture that is emerging is one of hurricanes that are not only getting stronger with greater wind damage and larger storm surge, but are more likely to stall upon landfall AND maintain their intensity after landfall, leading to increased flooding and damage.”
He continued: “At the core of the study is a really simple idea: Warmer oceans mean more entrained moisture, so even when the moisture ‘source’ (the warm ocean surface) has been ‘cut off’ (due to landfall), there is so much more moisture that the storms can continue to feed upon it and maintain their intensity.”
Suzana Camargo, a researcher at Columbia University’s Lamont-Doherty Earth Observatory in New York, said there is one significant caveat to the new research, which is that it looked only at storms in the Atlantic, where the most reliable data is to be found. “It would be important to repeat this analysis in other basins, in particular the Western North Pacific,” she said.
However, Massachusetts Institute of Technology hurricane expert Kerry Emanuel, whose work shows that tropical cyclones are becoming stronger in a warming world, said while he’s intrigued by the new paper, he would like to see more work done on this topic before he’s convinced that hurricanes are both spinning up faster and having more trouble slowing down.
“I am persuaded that this is an important problem but do not regard the results as definitive; more research will be necessary to confirm or refute the findings,” he said in an email.
The 2020 hurricane season has been a case study in the effects of ocean heat content on hurricane intensity, as nine storms so far have taken advantage of warm waters and ideal atmospheric conditions to rapidly intensify, including two storms that increased their wind speeds by 105 mph in just 36 hours. Hurricanes Laura, Delta and Zeta, for example, were intensifying as they approached land, making them more resistant to quickly losing intensity once cut off from the warm waters of the Gulf of Mexico.
According to James Elsner, a hurricane researcher at Florida State University, the new study lines up with other recent findings. “There is certainly much more that needs to be studied on this topic, but the paper is important in quantifying landfall decay rates and linking these rates to changes in ocean heat,” he said in an email. “And the results of this study are consistent with increasing property damage losses with increasing [sea surface temperatures].”
The authors, who did not respond to requests for comment, wrote that this is an area of interest for further research.
Including the new study, the broad, emerging picture of how global warming is affecting hurricanes is a discomforting one for coastal and inland residents alike.
Nature’s biggest, most intense storm systems are becoming more intense, dropping more rainfall, taking longer to wind down once they hit land, are forming in areas they didn’t used to and are making leaps in intensity that weren’t common just a few decades ago. There is also evidence that they are moving more slowly than they used to, dillydallying toward coastal areas.
All of this translates into a more perilous existence for the increasing population along coastal areas and for people living a few hundred miles inland.