New research, published in the journal Nature on Wednesday, shows that hurricanes all over the world are moving at a slower speed, resulting in a heightened potential for destruction, according to the Washington Post. The changes were observed over the past 65 years, with an average 10 percent reduction in speed between 1949 and 2016. The research points to Hurricane Harvey as a prime example. The storm remained in place over Houston for an unusually long period, unleashing many days of torrential rains that led to much of the destruction that occurred.
According to the study’s author, Jim Kossin of the National Oceanic and Atmospheric Administration:
“Every one of the hazards that we know tropical cyclones carry with them, all of them are just going to stick around longer. And so that’s never a good thing.”
Kossin decided to investigate whether such a phenomenon could be occurring as a result of climate change, which has already altered the atmospheric circulation that determines the movement of hurricanes and other storms. As temperatures have risen more rapidly at the poles than in regions closer to the equator, storm tracks could be expected to slow.
“I went in with that hypothesis and looked at the data, and out popped the signal that was much bigger than anything I was expecting,” he said.
The effect was worse in some regions than others. For example, the western North Pacific, near East Asia, saw the most substantial slowdown, at 20 percent, while storms in the North Atlantic slowed only 6 percent. The hurricanes slowed even more once on land than they did over oceans, moving 20 percent slower in the Atlantic region.
These changes come in addition to a predicted 7 to 10 percent increase in rain, for every degree Celsius of warming.
The 10 percent slowdown came alongside just a half degree Celsius of warming in the same period. Kossin suspects the slower movement may cause even more damage than the increased rainfall itself.
“It is plausible to say that the local rainfall impacts, the impacts from slowing, are equal to and possibly greater than the impacts from increased water vapor in the atmosphere,” said Kossin.
However other scientists, such as National Center for Atmospheric Research climate scientist Colin Zarzycki, have pointed out that there may be natural cycles in the climate system that shift over decades, which have nothing to do with climate change.
Kossin acknowledges this:
“My study is pretty far from an attribution study. I’m finding something that might be considered consistent [with climate change], but, really, no idea what’s contributing what to this signal. At least not yet.”
Zarzycki who reviewed the study, also notes that methods for studying hurricanes have changed over the decades, meaning some storms, particularly moving over oceans, could have been missed by the study’s analysis.
While there is more work to be done, the study suggests a higher potential for destruction in the future. Kossin notes:
“Inland flooding, freshwater flooding, is taking over as the key mortality risk now associated with these storms. There’s been a sea change there in terms of what’s dangerous. And, unfortunately, this signal would point to more freshwater flooding.”