Background
The authors note that "when a hurricane makes landfall, waves and storm surge can overtop coastal barriers, depositing sandy overwash fans on backbarrier salt marshes and tidal flats," and that long-term records of hurricane activity are thus formed "as organic-rich sediments accumulate over storm-induced deposits, preserving coarse overwash layers."

What was done
Scileppe and Donnelly refined and lengthened the hurricane record of the New York City area by first calibrating the sedimentary record of surrounding backbarrier environments to documented hurricanes - including the hurricanes of 1893, 1821, 1788 and 1693 - and then extracting several thousand additional years of hurricane history from this important sedimentary archive.

What was learned
The two researchers report that "alternating periods of quiescent conditions and frequent hurricane landfall are recorded in the sedimentary record and likely indicate that climate conditions may have modulated hurricane activity on millennial timescales." Of special interest in this regard, as they describe it, is the fact that "several major hurricanes occur in the western Long Island record during the latter part of the Little Ice Age (~1550-1850 AD) when sea surface temperatures were generally colder than present," but that "no major hurricanes have impacted this area since 1893," when the earth was in the initial stages of its transition from the Little Ice Age to the Modern Warm Period.

What it means
Noting that (1) Emanuel (2005) and Webster et al. (2005) have produced analyses that suggest that "cooler climate conditions in the past may have resulted in fewer strong hurricanes," but that (2) their own findings suggest just the opposite, Scileppe and Donnelly conclude that "other climate phenomena, such as atmospheric circulation, may have been favorable for intense hurricane development despite lower sea surface temperatures," prior to the development of the Modern Warm Period. Perhaps, therefore, we have much-maligned global warming to thank for the complete absence of major hurricanes in the vicinity of New York City over the past 114 years.

References
Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 436: 686-688.

Webster, P.J., Holland, G.J., Curry, J.A. and Chang, H.-R. 2005. Changes in tropical cyclone number, duration, and intensity in a warming environment. Science 309: 1844-1846.