Hate to say I told ya so. . . but I did

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-- Scientists linking the increased strength of hurricanes over recent years to global warming have not accounted for outdated technology that may have underestimated storms' power decades ago, researchers said in a report published Friday.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The study claims historical storm data has been rendered out-of-date by new technology that better estimates the strength of hurricanes.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.

Hey, Al. . . that's Inconvenient

CAPE CANAVERAL - Studies that link a spike in hurricane intensity with global warming are spotting "artificial upward trends" because they rely on bad historical data, a paper suggested today in the journal Science.

Hurricane intensity is measured by the storms' surface winds. Sometimes those winds are estimated by looking at satellite pictures, using a subjective technique invented in 1972.
Better technology since then, including greater satellite coverage, has led inevitably to higher wind-speed estimates for more recent storms, the authors suggest.

"The resulting higher resolution images and more direct overhead views of tropical cyclones result in greater and more accurate intensity estimates in recent years when using the Dvorak Technique," according to authors Christopher Landsea of the National Hurricane Center, Bruce Harper, Karl Hoarau and John Knaff.

For example, Hurricane Hugo's strength was underestimated based on images taken from an angle, and similar errors probably occurred frequently in the 1970s and 1980s, when there was less satellite coverage, the authors write.

While there may be trends in storm intensity linked to sea temperatures, which have increased, the "trends are very likely to be much smaller (or even negligible) than those found in the recent studies," the paper says.

An ongoing overhaul of the hurricane database may make it easier to quantify storm trends, the authors say