Hurricanes around the world are becoming slower and more static, staying longer on land or sea and dispensing greater amounts of rain, says a recently published study.
The information has nothing to do with the forces of the winds but with the speed at which the storm moves. In recent years hurricanes have been moving 10% more slowly compared to their speed in the 1940s and 1950s, says the study published by the journal Nature. The average speed of the storms in 2016 was 2 kilometers per hour (1.25 miles) slower than some 60 years ago.
In the Atlantic Ocean the difference was not so drastic, only 6%. But when those storms hit land, the discrepancy widened to 20%. Storms over the Atlantic that passed by land were on average about 4.7 km per hour (2.9 mph) slower than they were some 60 years ago.
“The slower a storm moves, the more rain it will throw on a specific site,” said study author James Kossin, a government-affiliated climatologist. “Hurricane Harvey last year was an excellent example of the havoc that a slow hurricane can cause.”
Harvey, who left at least 68 dead, posted a record 152 centimeters (60 inches) of rain in parts of southeast Texas, according to the National Hurricane Center.
Kossin began his study before the 2017 season, so his analysis only reaches 2016. If he had added hurricanes last year, the average slowness would be a little more pronounced, he said.
The slowness of the hurricanes also involves the repeated blowing of gales over the same locality, as well as higher tides, estimated Kossin.
The trend bears the telltale signs of climate change caused by human activity, Kossin said. But the study does not talk about causes or use computer models to observe damage on Earth with and without climate change. Instead, it relies exclusively on records achieved in the past, Kossin said.
Another recent study that did use computer models concluded that storms in the future will be slower due to climate change.
Climate change is altering the circulation of atmospheric winds, which are the ones that drive the storms, Kossin said.
However, other scientists were skeptical that the data recorded before the 1970s are unreliable. That’s why it’s difficult to reach those conclusions with certainty, said Brian McNoldy, a hurricane specialist at the University of Miami.