From
:http://www.earthsky.org/features/Sci...nesWarming.php

Experts respond to questions challenging link between global warming
and hurricanes

(July 28, 2006) A research meteorologist at the National Hurricane
Center today challenged a proposed link between global warming and
hurricane intensity, which had been reported earlier by other hurricane
researchers.

Two other hurricane scientists - whose research indicates this link
does exist, and that global warming is already causing stronger
hurricanes - have now responded.


Chris Landsea
Research meteorologist Chris Landsea called the existing data on
hurricanes "insufficently reliable" to be able to detect a connection
between global warming and the appearance of more intense hurricanes in
recent years.
Landsea wrote in the July 28, 2006 edition of Science, in a section of
the journal called "Perspectives." In his remarks, Landsea questioned
the objectivity of what's called the Dvorak Technique, a method of
estimating tropical cyclone intensity using satellite imagery.

"It is common for different forecasters and agencies to estimate
significantly different intensities on the basis of identical
information," Landsea wrote.

He wrote that data solely relying on satellites showed "artificial
upward trends in intensity," and that data inconsistencies cast "severe
doubts on any such trend linkages to global warming."


Judith Curry
Meanwhile, Judith Curry - a climate scientist at the Georgia Institute
of Technology, who recently testified before a U.S. congressional
committee on the subject of hurricanes and global warming - told Earth
& Sky, "Landsea's 'article' is commentary, not a peer reviewed
article."
She said, "The North Atlantic data clearly show that - in the last
decade (since 1995) relative to the decade centered around 1950
(previous peak period) - there are 50% more named storms, 50% more
hurricanes, and 50% more category 4 and 5 storms.

"WIth regard to the global data since 1970 ... there have been
variations with time in how the data has been processed. There is
anecdotal evidence that some storms have been misclassified (some
classified to high and some too low).

"However, at this point, no one has done a rigorous error or
uncertainty analysis on the data, so in my opinion Landsea's statements
about the trends are not supported."


Kevin Trenberth
Kevin Trenberth - head of the Climate Analysis Section at the National
Center for Atmospheric Research - told Earth & Sky, "There are still
good reasons to believe that hurricanes have become more intense, and
that this trend will continue."
He said, "The data on sea surface temperatures, and on water vapor in
the atmosphere, are sound. Sea temperatures have risen. Water vapor has
increased about 4% since 1970 over the oceans.

"This is fuel for storms, including the extratropical storms that
caused floods in New England earlier this year and in Washington D.C.
this summer.

"There is no question about the changes of huge increases in intensity
and duration of storms, as found by Kerry Emanuel. For Landsea to
suggest otherwise has no credence.

"Moreover, as we have published, this is associated with increases in
sea surface temperatures and that is mostly caused by global warming,
not natural variability," he concluded.


Tom Knutson
Tom Knutson of NOAA's Geophysical Fluid Dynamics Lab also weighed in.
In an email to Earth & Sky, he said, " I would not claim to have the
expertise to decide who is closer to the truth in this particular
debate at this point."
He continued, "The issue of data homogeneity is a very legitimate and
important question to raise concerning the issue of possible long-term
trends in hurricane activity."