http://www.usatoday.com/weather/climate/globalwarming/2008-05-18-

global-warming-hurricanes_N.htm

Study says global warming not worsening hurricanes

By Seth Borenstein, AP Science Writer

WASHINGTON — Global warming isn't to blame for the recent jump in

hurricanes in the Atlantic, concludes a study by a prominent federal

scientist whose position has shifted on the subject.

Not only that, warmer temperatures will actually reduce the number of

hurricanes in the Atlantic and those making landfall, research

meteorologist Tom Knutson reported in a study released Sunday.

In the past, Knutson has raised concerns about the effects of climate

change on storms. His new paper has the potential to heat up a

simmering debate among meteorologists about current and future

effects of global warming in the Atlantic.

Ever since Hurricane Katrina in 2005, hurricanes have often been seen

as a symbol of global warming's wrath. Many climate change experts

have tied the rise of hurricanes in recent years to global warming

and hotter waters that fuel them.

Another group of experts, those who study hurricanes and who are more

often skeptical about global warming, say there is no link. They

attribute the recent increase to a natural multi-decade cycle.

What makes this study different is Knutson, a meteorologist with the

National Oceanic and Atmospheric Administration's fluid dynamics lab

in Princeton, N.J.

He has warned about the harmful effects of climate change and has

even complained in the past about being censored by the Bush

administration on past studies on the dangers of global warming.

He said his new study, based on a computer model, argues "against the

notion that we've already seen a really dramatic increase in Atlantic

hurricane activity resulting from greenhouse warming."

The study, published online Sunday in the journal Nature Geoscience,

predicts that by the end of the century the number of hurricanes in

the Atlantic will fall by 18%.

The number of hurricanes making landfall in the United States and its

neighbors — anywhere east of Puerto Rico — will drop by 30% because

of wind factors.

The biggest storms — those with winds of more than 110 mph — would

only decrease in frequency by 8%. Tropical storms, those with winds

between 39 and 73 mph, would decrease by 27%.

It's not all good news from Knutson's study, however. His computer

model also forecasts that hurricanes and tropical storms will be

wetter and fiercer. Rainfall within 30 miles of a hurricane should

jump by 37% and wind strength should increase by about 2%, Knutson's

study says.

And Knutson said this study significantly underestimates the increase

in wind strength. Some other scientists criticized his computer model.

MIT hurricane meteorologist Kerry Emanuel, while praising Knutson as

a scientist, called his conclusion "demonstrably wrong" based on a

computer model that doesn't look properly at storms.

Kevin Trenberth, a climate scientist, said Knutson's computer model

is poor at assessing tropical weather and "fail to replicate storms

with any kind of fidelity."

Trenberth, climate analysis chief at the National Center for

Atmospheric Research in Boulder, Colo., said it is not just the

number of hurricanes "that matter, it is also the intensity, duration

and size, and this study falls short on these issues."

Knutson acknowledges weaknesses in his computer model and said it

primarily gives a coarse overview, not an accurate picture on

individual storms and storm strength. He said the latest model

doesn't produce storms surpassing 112 mph.

But NOAA hurricane meteorologist Chris Landsea, who wasn't part of

this study, praised Knutson's work as "very consistent with what's

being said all along."

"I think global warming is a big concern, but when it comes to

hurricanes the evidence for changes is pretty darn tiny," Landsea

said.

Hurricane season starts June 1 in the Atlantic and a Colorado State

University forecast predicts about a 50% more active than normal

storm season this year. NOAA puts out its own seasonal forecast on

May 22.

In a normal year about 10 named storms form. Six become hurricanes

and two become major hurricanes. On average, about five hurricanes

hit the United States every three years.

Copyright 2008 The Associated Press. All rights reserved. This

material may not be published, broadcast, rewritten or redistributed.

posted to ClimateConcern by Jim