Text 21429, 78 rader
Skriven 2006-07-29 19:32:00 av Jeff Binkley (1:226/600)
Ärende: More hurricanes
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http://www.sun-sentinel.com/news/local/southflorida/sfl-
0729globalwarming,0,3801546.story?coll=sfla-home-headlines

Global warming's effect on hurricane strength disputed in new report

The Associated Press 
Posted July 28 2006, 4:09 PM EDT 

MIAMI -- Scientists linking the increased strength of hurricanes over 
recent years to global warming have not accounted for outdated 
technology that may have underestimated storms' power decades ago, 
researchers said in a report published Friday.

The research by Chris Landsea of the National Hurricane Center 
challenges two studies published last year by other respected 
climatologists.

 
One of the studies, by Kerry Emanuel of the Massachusetts Institute of 
Technology, was considered the first major research to challenge the 
belief that global warming's affect on hurricanes was too slight to 
accurately measure and that climate change likely won't substantially 
change tropical storms for decades.

And, if Landsea and his three co-authors are correct, it was 
fundamentally flawed.

``The methodology is fine. There's no problem with the way they analyzed 
the data,'' said Landsea, who is science and operations officer at the 
hurricane center. ``The problem is with the data itself.''

The study claims historical storm data has been rendered out-of-date by 
new technology that better estimates the strength of hurricanes. He 
pointed to advancements in the quality of satellite imagery that is used 
to estimate a storm's strength when it can't be directly measured by 
aircraft or on land.

In short, Landsea said, there were far more Category 4 and 5 storms in 
decades past than previously thought, because satellite imagery has 
improved so greatly.

The article was published in the journal Science. It is co-authored by 
Bruce Harper, an Australian engineer who is an expert on Pacific 
cyclones; Karl Hoarau, a professor at Cergy-Pontoise University in 
France; and John Knaff, a researcher at the National Oceanic and 
Atmospheric Administration. It looks at only a small sampling of 
historical storm data, though the authors plan to examine further 
hurricane information they believe will further prove their thesis.

Emanuel discounted the Science piece and said he put considerable effort 
into accounting for changes in estimating storm strength.

``They ignore the most significant finding from my Nature paper _ that 
Atlantic hurricane activity is highly correlated with sea surface 
temperature, which is comparatively well-measured,'' Emanuel said by e-
mail from the Queen Mary 2, where he is lecturing on storms. ``This 
cannot be explained away by invoking rather qualitative arguments about 
data quality.''

Emanuel analyzed records of storm measurements made by aircraft and 
satellites since the 1950s. He found the amount of energy released in 
these storms in both the North Atlantic and the North Pacific oceans 
increased, especially since the mid-1970s.

His study was published last year, along with another Science piece that 
linked a double in Category 4 and 5 hurricanes since 1970 to the rise of 
ocean surface temperatures.

Landsea said he did not dispute global warming was occurring or that it 
could influence hurricanes; he said it simply was not proven by the 
storm information available.

The studies did not address fluctuation in the number of hurricanes, 
only in their intensity. But researchers agree that the Atlantic basin 
is in a period of higher hurricane activity that could last decades. 

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