Global warming update

Scientist Shifts View on Global Warming
By SETH BORENSTEIN,AP
Posted: 2008-05-18 15:55:50
Filed Under: Science News
WASHINGTON (May 18) - 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 percent.

The number of hurricanes making landfall in the United States and its
neighbors - anywhere east of Puerto Rico - will drop by 30 percent
because of wind factors.

The biggest storms - those with winds of more than 110 mph - would
only decrease in frequency by 8 percent. Tropical storms, those with
winds between 39 and 73 mph, would decrease by 27 percent.

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 percent and wind strength should increase by about 2
percent, 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 percent 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.


.

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