Global Warming could mean fewer hurricanes
by Justin Caudell
The debate over Global Warming is likely about to get more interesting.
According to the National Oceanic and Atmospheric Association (NOAA),
new findings by climate scientists show that a warming global ocean could
mean fewer Atlantic hurricanes will strike the United States in the future.
A discovery contrary to past beliefs that thought tropical systems like
Hurricane Katrina were at the result of a rise in world temperatures.
The study, which was recently released in Geophysical Research Letters,
uses observations to show that warming of global sea surface temperatures is
associated with a secular, or sustained long-term increase, of vertical wind
shear in the main development region for Atlantic hurricanes – thus
distracting storms from forming.
The increased vertical wind shear is believed to coincide with a downward
trend in U.S. land falling hurricanes over the past two years.
“We looked at U.S. land falling hurricanes because it is the most reliable
Atlantic hurricane measurement over the long term,” says Chunzai Wang, a
physical oceanographer and climate scientist with NOAA’s Atlantic
Oceanographic and Meteorological Laboratory in Miami, Florida and lead
author on the article. “Using data extending back to the middle nineteenth
century, we found a gentle decrease in the trend of U.S. land falling
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. land falling hurricanes.”
For the article, Wang worked with Sang-Ki Lee of the Cooperative Institute
for Marine and Atmospheric Studies at the University of Miami.
In terms of hurricane strength, Wang notes, “The vertical wind shear is not
the only factor affecting Atlantic hurricane activity, although it is an important
one.”
Other factors include atmospheric humidity, sea level pressure, and sea
surface temperature.
The study also suggests that where the global ocean warming occurs is
important for determining the vertical wind shear in the Atlantic hurricane main
development region - within the 10°-20° North latitude belt that stretches from
West Africa to Central America.
NOAA observations from 1854 to 2006 show a warming of sea surface
temperature occurring almost everywhere over the global ocean, with large
warming in tropical regions of the Pacific, Atlantic, and Indian oceans.
The warmer waters in the tropical Pacific, Indian and North Atlantic oceans
produce opposite effects upon vertical wind shear; that is, warming in the
tropical Pacific and Indian oceans increase vertical wind shear in the Atlantic
hurricane main development region, while warming in the tropical North
Atlantic decreases vertical wind shear.
Overall, the study concluded that the warming in the Pacific and Indian
oceans is of greater impact and produces increased levels of vertical wind
shear which suppresses Atlantic hurricane activity.
Whether future global warming could increase Atlantic hurricane activity in
the future is said to probably depend on the relative role induced by
sustained long-term warming over the tropical oceans according to Wang.