A HISTORY OF NATURE’S TERRORISM
Digging into the past to predict the future of hurricane activity

Long before mankind developed official record keeping methods, sophisticated satellite technology, and supercomputing, hurricanes ravaged the Gulf of Mexico and Atlantic Ocean coasts of North America, as well as places from Asia to Australia. Documenting storms was not something that took place.

Now, in the twenty-first century, preparing for and keeping a close eye on storms is a task to which all who live along coastlines are accustomed. One LSU researcher is keeping an even closer eye on hurricane activity, looking back to 5,000 years ago in search of clues to help determine what our future hurricane activity will be and when New Orleans and other places along the Gulf Coast could be hit by a storm stronger than Hurricane Katrina.

For the past 15 years, Kam-biu Liu, the LSU James J. Parsons Professor of Geography, has been using coastal sediments deposited over the last five millennia to find a geological fingerprint of hurricane activity. Liu’s new, emerging field of research is known as paleotempestology, which is the science of studying tropical storm activities of the past.

“It is crucial that we are prepared for these natural terrorists: hurricanes,” says Liu, known to many as a pioneer in paleotempestology. “Before Katrina, New Orleans was never hit by a category 4 or 5 storm, so this research will give us a glimpse of what we may expect in the next decade, century, five centuries, and millennium.”
Every time an intense hurricane makes landfall, the storm surge sweeps sand from the beach and dunes into coastal lakes and marshes, which forms a sand layer. Liu and his research team take a core sample of the sediment in the marsh or at a lake bottom, exposing each layer of sand and with it, the number and strength of hurricanes that have hit that particular area. Using radio-carbon dating, Liu can determine when the layers were formed and how many hurricanes have hit the coast for the past five millennia.

Based on his findings, Liu says that catastrophic hurricanes—those of category 4 or 5—hit the U.S. coast about once every 300 years on average. The last millennium has had a relatively low occurrence of hurricanes, whereas the period of 1,000 to 3,800 years ago shows a dramatic increase in hurricane activity on the U.S. Gulf coast. Though he looks at mostly millennial scales, Liu also examines decade-long cycles, noting that when the Atlantic Coast is having a turbulent decadal cycle, the Gulf Coast is comparatively calm, and vice versa. He thinks that this see-saw pattern of hurricane activity also occurs on the millennial timescale.

Liu maintains that the key question to his research is ultimately about global changes over time.

“We want to know what are the climatic mechanisms that cause such shifts in hurricane activity from one millennium to another and one decade to another,” says Liu.

Insurance companies are also greatly interested in work like Liu’s. The Risk Prediction Initiative (RPI), housed in the Bermuda Biological Station for Research, was formed as a collaboration between scientists and insurance companies to support research on hurricane frequency and future strike probabilities. RPI, as well as the National Science Foundation and the Inter American Institute for Global Change Research, are all funding Liu’s work—better enabling him and his team to paint a picture of how catastrophic our hurricane future could be. –J.T. Lane

ON THE WEB:
Professor Kam-biu Liu’s Homepage

from Storm Issue 2005