The BBC News is reporting on a new study of annual hurricane activity, going back over 1,500 years, that has just been published in the journal Nature (press release). According to the study, which was conducted by a team led my Dr. Michael Mann, of Penn State University, the number of hurricanes that have crossed the shoreline in the last ten years represents a peak comparable to one seen about 1,000 years ago. Thus, there is evidence to support a natural, long-period cycle in the amount of hurricane activity in the Atlantic.
The study looked at what is called “overwash” – debris from the shore that is picked up by the storm and carried inland, into a lagoon or other body of water. The sediment deposited can be dated via radio-carbon techniques. The team also used a computer model to examine its correspondence with the historical data.
The model includes three factors known to be important in determining hurricane formation: sea surface temperature in the tropical Atlantic Ocean, the El Nino/La Nina cycle in the eastern Pacific, and another natural climatic cycle, the North Atlantic Oscillation.
Unfortunately, the interplay of these factors is not completely understood. But this research should contribute some pieces of the puzzle.