"
From 1970 to 1995, there weren't that many hurricanes, and the ones we had were nice, well-mannered,
housebroken hurricanes that stayed out to sea and didn't make a mess," said Hugh Willoughby, a hurricane
researcher at Florida International University in Miami.
"The only thing I can say," he added, "is
this run
of good luck we had is ending."
"
This year you can just say nature is averaging out its climatology,"
said Colorado State University's famed hurricane predictor, William Gray.
(
See video of
the science of the storm --3:55)
Katrina and Rita are what Gray calls "Bahama busters," storms that
form off the Bahamas rather than near the coast of Africa. They explode after feeding on the warm waters of the Gulf
of Mexico.
The past century saw 18 "Bahama busters," Gray said.
Even Katrina's and Rita's back-to-back
pounding of the Gulf Coast has a precedent. In 1915, Gray said, New Orleans and Houston areas were hit by Category 4
storms six weeks apart.
"
You can't blame that on global warming," he observed.
Gray first sounded
the alarm in 1995, noting that the surface waters in the north Atlantic Ocean had warmed slightly. 1995 saw 11
hurricanes and eight tropical storms, the highest tally since 1933.
By 1997, Gray's annual forecasts warned of
"a new era" of hurricanes.
He put forth the theory that many climatologists, including Mayfield and Willoughby,
now embrace -- that
hurricanes are driven by cycles of rising water temperature and salinity that affect the
speed of currents in the Atlantic.
The
technical name for the engine driving the hurricane cycles is the
Atlantic Multidecadal Oscillation, or AMO for short. It can cause droughts in the West and hatch hurricanes in
the East.
"
This cycle has been repeating back to the Ice Age," Willoughby said. "It's related to changes
in the ocean currents that move heat northward. If it's fast, we get a lot of hurricanes."
Studies show the AMO
was cool -- and the currents slower -- from 1900 to 1925, warm from 1926 to 1969, cool from 1970 to 1994 and warm
since 1995.
And so, to a generation of Americans with little experience with hurricanes, it seems like these
monsters are coming out of nowhere.
Gray and Willoughby are among the skeptics who doubt global warming can be
blamed for the trend of the past few years. They are joined by the hurricane trackers at the National Hurricane
Center.
"
We're just entering a busy time here," said Chris Lauer, a meteorologist at the
center.
"You see a few decades of slower activity, followed by a few decades of higher oscillation," he said.
"Our position is the recent increase in hurricane activity is not caused by global warming."
Researchers at
the Georgia Institute of Technology in Atlanta, Georgia, suggested earlier this month that more than nature and
coincidence might be driving the storms
In the September's issue of the journal Science, Peter Webster and
Judith Curry documented a
60 percent global jump in major hurricanes with winds of 131 mph or more and a 1-degree
increase in the tropical ocean surface temperature.
But Webster warned on Georgia Tech's Web site that
more study was needed before blaming global warming.
"We need a longer data record of hurricane statistics,"
he said, "and we need to understand more about the role hurricanes play in regulating the heat balance and
circulation in the atmosphere and oceans."
Willoughby said he is keeping an open mind about the role of
global warming but believes it won't be a factor for at least another 100 years.
"The answer I give
everybody, because
it has all been so politicized, is I don't know," he said.
Gray was more direct.
"
There are all these medicine men out there who want to capitalize on general ignorance on this subject," he
said.
"
With all the problems in the world, we shouldn't be dealing with this."
Willoughby believes
the debate over hurricanes and global warming is healthy. "It's good for the science," he said.
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