The coming week is the statistical peak for hurricane activity in the Atlantic Basin. However, an expert in the history of weather and weather patterns says we are also now experiencing a level of hurricane activity not seen in one thousand years.
Professor Michael Mann works in the Penn State Department of Meteorology and Geosciences, and also directs the Penn State Earth System Science Center.
Mann says that by carefully studying the "deposit records" of certain types of soil, we can get some insight in to how often major hurricanes have struck North America.
He says scientists have carefully studied mud and silt layers going back thousands of years in protected lagoons, which have not been open to the ocean for thousands of years.
"In these layers, every once in a while, you'll see a thin layer of fine sand," Mann said. "Typically the only thing strong enough to do that is a very strong hurricane."
Mann theorizes that the layers of fine sand, blown in from the shore, act as a historical record of for hurricanes, showing that the Atlantic Basin has not seen this frequency of strong storms in a thousand years.
Listen to WWL's Jay Vise's conversation with Prof. Mann:
But, are storms also getting stronger? Mann says the evidence points in that direction.
"We know that we are locally at a high point," for the last thousand years, Mann said.
"There is this close relationship between over even longer time scales, between sea-surface temperatures... and tropical cyclone activity," he said.
Mann does believe that global warming is contributing to warmer seas, and therefore contributing to more frequent and possibly stronger storms.
However, we asked him if global warming is causing a thousand-year high in tropical activity, then what caused the previous peak before man had even invented the means to produce "greenhouse gases?"
Mann said that although he the previous peak of tropical activity was the entirely the work of Mother Nature-induced prolonged La Nina effect, it's possible that those same historical conditions could now be combining with the possible effects of human activity to either make the tropical activity either more or less frequent.
"It's not contradictory, but that's an important observation," Mann said. "What it tells us is that we have not yet exceeded the envelope of natural vaiability.. If we go a thousand years ago, back that far...we really had this almost interesting, "conspiracy" of factors that caused that peak."
"We don't know if human-caused climate change will give us those La Nina-like conditions," according to Mann. "There is very much a debate within the scientific community about whether climate change will lead to a more El Nino-like future, or a more La Nina-like future.
To view Professor Mann's research and article on the topic as published in Nature, please click the following link:
http://www.meteo.psu.edu/~mann/shared/articles/MannetalNature09.pdf
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