Every now and then what we know and thought we knew about science gets turned on its head. And while this particular story isn’t necessary as head-turning as some, it is definitely throwing the academic world in to a spin.
According to new research to be published on the 23rd in Geophysical Research Letters, the warming of the global ocean could actually mean fewer Atlantic hurricanes making landfall in the US, rather than the hitherto believed concept that more would make landfall.
Using observations collected over a hundred years, compared to computer models, the National Oceanic and Atmospheric Administration in the US has somewhat convincingly shown that increased temperatures link to increased vertical wind shear in the Atlantic Ocean. Wind shear is the change in wind and speed direction, and is a hindrance to the formation of hurricanes.
Chunzai Wang, a physical oceanographer and climate scientist with NOAA’s Atlantic Oceanographic and Meteorological Laboratory in Miami, was the lead author of the study.
“We looked at U.S. landfalling hurricanes because it is the most reliable Atlantic hurricane measurement over the long term,” said Wang. “Using data extending back to the middle nineteenth century, we found a gentle decrease in the trend of U.S. landfalling hurricanes when the global ocean is warmed up. This trend coincides with an increase in vertical wind shear over the tropical North Atlantic and the Gulf of Mexico, which could result in fewer U.S. landfalling hurricanes.”
Wang adds, regarding hurricane strength, “The vertical wind shear is not the only factor affecting Atlantic hurricane activity, although it is an important one.”
The study also posits that just where the global ocean warming takes place is an important factor in determining the wind shear in the Atlantic hurricane main development region. This region is within the 10°-20° North latitude belt that stretches from West Africa to Central America.
The observations, taken between 1854 and 2006, show a warming of the sea surface temperature taking place almost globally. Increased warming took place in tropical regions of the Pacific, Atlantic and Indian oceans. Warmer waters in the tropical Pacific, Indian and North Atlantic all had opposite effects upon vertical wind shear; ie, warming in the tropical Pacific and Indian oceans increased vertical wind shear in the Atlantic, thus hampering the formation and continued strengthening of hurricanes.
However critics are striking out at Wang’s study data, saying that it is “poor” and is the same data that was rejected by the Nobel Prize-winning Intergovernmental Panel on Climate Change. They reinforce their opinions by noting that only one in ten North Atlantic storms make landfall on the US coast, and thus reflects only a small percentage of storms around the globe.
Hurricanes hitting land “are not a reliable record” for how hurricanes have changed, said Kevin Trenberth, climate analysis chief for the National Center for Atmospheric Research in Boulder, Colo.
Photo Courtesy of NOAA