For years, atmospheric scientists have speculated as to how hurricanes might change as the climate warms.
Ocean surface temperature is on the rise, suggesting hurricanes will become more intense in the future. How other atmospheric factors will change — like hurricane-dampening wind shear — remains somewhat of a question mark, injecting doubt into the simple “warmer oceans means stronger hurricanes” argument.
And in the end, hurricane-climate change debates are usually punctuated by one point — we just don’t have enough years of good data on record to understand how hurricanes might change in our warming future. The best hurricane records we have only go back to the early 20th century, and are murky at best before 1950.
But a new study has taken what we know about past hurricanes to new lengths, and found that intense storms — more powerful than anything New England has seen in recorded history — were much more frequent during the first millennium, possibly fueled by periods of very warm ocean temperatures.
Using new sediment records from Cape Cod, researchers pieced together the East Coast’s stormy past. Buried in the sand was evidence of unprecedented hurricane activity. Twenty three severe hurricanes — category 3 or 4 — were found to have struck New England between the years 250 and 1150 A.D. The average rate of severe hurricane strikes was approximately one every 40 years during this time.
“These records suggest that the pre-historical interval was unlike what we’ve seen in the last few hundred years,” said Jeff Donnelly, a scientist at Woods Hole Oceanographic Institute, and lead author of the study.
The study may emphasize the danger in becoming complacent about hurricane landfalls. The United States hasn’t seen a major hurricane landfall — category 3 or stronger — since Wilma in 2005. Hurricane Bob, a category 2 in 1991, was the strongest hurricane to make landfall in the Northeast since 1950.
While Hurricane Sandy was an epic storm by a variety of measures, wind speed wasn’t one of them. Sandy was just the equivalent of a category 1 when it pushed ashore in 2012, and yet it was the second costliest hurricane in U.S. history.
Even Florida, the country’s most vulnerable, tropically-located state, hasn’t seen a hurricane landfall in nine years.
This is all to say that the East Coast has had but a taste of extreme storms over the past few decades, and it might be worth considering the possibility of something much stronger and more frequent. “We hope this study broadens our sense of what is possible and what we should expect in a warmer climate,” Donnelly said. “We may need to begin planning for a category 3 hurricane landfall every decade or so rather than every 100 or 200 years.”
“The risk may be much greater than we anticipated,” he added.