Dangerous storms in the warming Atlantic Ocean are intensifying faster and are more than twice as likely to grow into major hurricanes as in the past, a new study has found.
Rapid increase in maximum sustained wind speed characterizes many, though not all of those storms, known as tropical cyclones. It makes them harder to forecast and harder to plan for. Also, cyclones that undergo rapid intensification tend to be more intense when they make landfall, where they have wreaked billions of dollars in damage and killed hundreds of people over the last decade.
The six costliest climate disasters over that time in the United States — Superstorm Sandy was among them, killing at least thirteen Long Islanders and damaging or destroying 100,000 homes in the region — all strengthened rapidly, evolving from tropical storms to major hurricanes in under three days.
“These findings illustrate a vital need to not only work towards climate mitigation to limit future warming and thus additional changes in (tropical cyclone) intensification rates, but also for emergency preparedness plans and resilience measures that will allow our coastlines to adapt,” wrote the study’s author, Andra Garner, an assistant professor in the Department of Environmental Science at Rowan University in New Jersey.
The study was published Thursday in Nature’s “Scientific Reports,” a peer-reviewed journal.
Kevin Reed, associate dean for research at Stony Brook University’s School of Marine and Atmospheric Sciences, said the paper added to the body of research from around the world showing that hurricanes are becoming stronger. “This study provides additional evidence that global climate change is increasing the damage potential of hurricanes, and tropical cyclones more generally,” he said in an email.
“The next time a hurricane is tracking toward Long Island, it might be stronger than a similar hurricane from 30 or 40 years ago would have been.”
The study analyzed National Oceanic and Atmospheric Administration wind speed data compiled from 1971 to 2020 for tropical cyclones, spinning storms that develop over tropical or subtropical waters, powered by the ocean’s heat and low temperatures in the upper atmosphere. A hurricane is a tropical cyclone with sustained surface winds of at least 74 mph.
Between 1971 and 1990, tropical cyclones had a roughly 3% chance of intensifying into a major hurricane in a 24-hour window; between 2001 and 2020, considered the modern era, that chance had risen to about 8%.
A major, or Category 3 hurricane, has sustained winds of at least 111 mph. Its damage may include ruined homes, snapped trees, blocked roads and days or weeks of power outages.
Garner also found it was more likely for modern-era storms to strengthen at an accelerated pace even when that intensification didn’t put them into the hurricane-strength category.
The fastest tropical cyclone intensification rates often occur in areas with warm upper ocean and sea surface temperatures. Sea surface temperatures across the globe and in the North Atlantic hit historic records this year, but temperatures have been rising since the start of the 20th century at an average rate of 0.14 degrees per decade, according to NOAA.
Heat is energy and “really warm ocean waters act as fuel,” Garner said in an interview. “When you have a tropical cyclone, or some low-pressure disturbance traveling over the waters, more moisture is evaporated into the air and those warm, moist parcels of air rise more quickly through the atmosphere … Then they are able to release some of that energy as they start forming thunderstorms and clouds.”
Garner also found that over time, the locations where tropical cyclones intensify most rapidly had changed. They have become more likely to intensify off the U.S. Atlantic coast, in the tropical eastern Atlantic and the southern Caribbean Sea. They were less likely to intensify in the Gulf of Mexico in the modern era than they had been from the 1970s to the 1990s.
“This means that coastlines along the Atlantic need to be thinking about how to prepare,” she said.