Controversial study says hurricanes more common

[jasons2k]

http://www.chron.com/disp/story.mpl/met ... 69904.html

Controversial study says hurricanes more common

By ERIC BERGER
HOUSTON CHRONICLE
Aug. 12, 2009, 12:00PM

Atlantic hurricanes have developed more frequently during the last decade than at any point in at least 1,000 years, a new analysis of historical storm activity suggests.

The new study, being published Thursday in Nature, attempts to reconstruct Atlantic hurricane activity back to the year A.D. 500. In doing so the authors found one era, a medieval period around A.D. 1000, when storm activity matched or exceeded recent hurricane seasons that included storms such as Katrina and Rita.

The scientists used two methods to reconstruct hurricane activity from a period when there were no satellites, reliable ship records or coastal residents taking notes.

One tack is based on the observation that the powerful storm surge of large hurricanes deposits distinct layers of sediment in coastal lakes and marshes. By taking cores of sediments at the bottom of these lakes, which span centuries, scientists believe they can tell when large hurricanes made landfall at a particular location.

The second method used a computer model to simulate Atlantic storm counts based upon historical Atlantic sea surface temperatures, El Niños and other climate factors.

The two independent estimates of historical storm activity were consistent, said Pennsylvania State University climate scientist Michael Mann, the paper's lead author. Both, for example, pinpointed a period of high activity between A.D. 900 and 1100.

“This tells us these reconstructions are very likely meaningful,” he said.

This is not Mann's first attempt to use “proxies” for actual observations of conditions to tease out historical climate details.

He was among the scientists whose global temperature reconstruction of the last 1,000 years — dubbed the “hockey stick graph” because it showed a distinct upward trend since the mid-19th century attributed to greenhouse gases — received both praise and criticism.

Now he appears to be doing the same with hurricane activity, and the new work is not without its detractors.

“The paper comes to very erroneous conclusions because of using improper data and illogical techniques,” said Chris Landsea, science and operations officer at the National Hurricane Center.

In his criticism, Landsea notes that the paper begins by saying that Atlantic tropical activity has “reached anomalous levels over the past decade.”

This ignores recent work by Landsea and a number of other hurricane scientists who found that storm counts in the early 1900s — in an era without satellites and fewer sea-borne observers — likely missed three or four storms a year. The addition of these storms to the historical record, he said, causes the long-term trend over the last century to disappear.

“This isn't a small quibble,” he said. “It's the difference between a massive trend with doubling in the last 100 years, versus no trend.”

Other scientists suggested that the new Nature paper does the best it can in deriving information about historical hurricane activity from a scant amount of data.

Yet this limits how useful the information is, said Rob Korty, an atmospheric scientist at Texas A&M University.

“The bottom line is that I think their work adds new and helpful information,” Korty said. “But we must keep in mind the assumptions this kind of work require are large by nature.”

eric.berger@chron.com

[RL3AO]

Atlantic hurricanes have developed more frequently during the last decade than at any point in at least 1,000 years


I stopped reading there.

[jasons2k]

Atlantic hurricanes have developed more frequently during the last decade than at any point in at least 1,000 years
I stopped reading there.

It's a well-balanced article. Read the 2nd half too (with comments from Chris Landsea)

[x-y-no]

Well, it's an interesting approach to the question, but I'd need to see a lot of support for the reliability of these proxies before I take it too seriously.

[JPmia]

I think the guy from Texas A&M, Rob Korty, said it best. Good article. Would be interested in reading the study. We shouldn't outright dismiss scientific studies until we actually read them, geez lol.

[Aslkahuna]

The period around the end of the First Millenium CE is also when the Medieval Maximum of Solar activity occurred and when there was apparently a significant warm period at least hemispherically.

Steve

[lurkey]

http://www.nytimes.com/2009/08/13/scien ... .html?_r=1


An ‘Increase’ in Big Storms May Just Be Better Detection

By CORNELIA DEAN
Published: August 12, 2009
Since the mid-1990s, hurricanes and tropical storms have struck the Atlantic Ocean with unusual frequency — or have they? Two new studies suggest that the situation may not be so clear.

One, by researchers at the National Oceanic and Atmospheric Administration, suggests that the high number of storms reported these days may reflect improved observation and analysis techniques, not a meteorological change for the worse. The second, by researchers at Pennsylvania State University and elsewhere, suggests that there were as many storms a thousand years ago, when Atlantic Ocean waters were unusually warm, as today.
The work does not suggest that people should stop worrying about whether global warming increases the threat of bad weather on the Atlantic Coast. But it offers new evidence that predicting what lies ahead may be difficult.

In findings reported this week in The Journal of Climate, the NOAA researchers, led by Christopher W. Landsea, say that several disturbances logged in 2007 and 2008 as tropical storms would never have been identified without satellite observations and new analysis techniques.

The researchers studied storms that played themselves out at sea, either in a day or two or over a longer period, from 1878 to 2008. By the late 19th century, they estimated, meteorologists missed perhaps two of the larger storms each year, and by the 1950s they were picking up on average all but one each year.

Yet the researchers estimate that a century ago, as many as 80 percent of short-lived storms came and went without ever being officially noticed.

Over all, they conclude, storm counts have not changed in the last century.

The other study, described in Thursday’s issue of the journal Nature, used a mathematical model of hurricane activity and measurements of sediment deposits to estimate how often major storms struck the Gulf and Atlantic Coasts of the United States in the last 1,500 years. Led by Michael E. Mann of Penn State, the researchers worked with sediment samples from Puerto Rico, the Gulf Coast and the Atlantic Coast from Florida to New England.

Although current numbers are relatively high, they say, both analytical methods suggest that a period of high storm frequency, possibly even higher than today’s, began in the year 900 and lasted until 1200 or so.

The NOAA researchers said their study did not address whether storms would be more powerful in a warmer world. Many researchers believe that such a shift is likely, given that hurricanes and tropical storms draw their energy from the heat of the oceans.

And if today’s ocean warming creates the conditions that prevailed a thousand years ago, Dr. Mann said in a statement, “it may not be just that the storms are stronger, but that there may be more of them as well.”

[jinftl]

Not sure that this is so controversial....how on earth can the 1,000 year assertion be proven?

More hurricanes have developed during the last decade than in any other decade of my life....born in the 1970s....but even that can't be that controversial....it's true....how could anyone argue otherwise?