We begin our analysis of this topic with the study of Liu and Fearn (2000), who analyzed several sediment cores obtained from Western Lake, Florida, USA to produce a 7000-year record of intense hurricane (category 4 or 5) strikes for this region of the US Gulf Coast.  Their study revealed that only twelve such storms had struck land there over this entire length of time, and that none of those strikes occurred during the first half of the record, which was the warmest period of the current interglacial or Holocene.

In an earlier study, Liu and Fearn (1993) had similarly analyzed a number of sediment cores that had been extracted from Lake Shelby, Alabama, USA, which covered the past 3500 years when much cooler temperatures had prevailed and all of the category 4 and 5 hurricanes at Western Lake, Florida had occurred.  Over this latter period they found that such storms had hit Alabama at "an average recurrence interval of ~600 years," the last of which occurred about 700 years ago following the demise of the Medieval Warm Period.

Moving closer to the present, Boose et al. (2001) used historical records to reconstruct hurricane damage regimes for the area composed of the six US New England states plus adjoining New York City and Long Island for the period 1620-1997.  In their study, there were not enough intense hurricanes to discern any trends; and in the case of less intense storms, the records of the 17th and 18th centuries were not considered to be as reliable as those of the last 200 years.  Focusing on this latter period, therefore, we note that the cooler 19th century experienced five category 3 storms, while the warmer 20th century experienced but one.

Elsner et al. (2000) developed a similar history of major hurricane strikes of Bermuda, Jamaica and Puerto Rico, finding far fewer such storms in the last half of the 20th century than in all five of the preceding 50-year periods.  From 1701 to 1850, for example, when the earth was locked in the chilling grip of the Little Ice Age, the frequency of major hurricane occurrence was fully 2.8 times greater than it was from 1951 to 1998; and from 1851 to 1950, when the planet was in transition from the Little Ice Age to the Modern Warm Period, it was 2.2 times greater.

In response to the well-documented global warming of the last hundred years, Easterling et al. (2000) report that "the number of intense and landfalling Atlantic hurricanes has declined."  This is also the conclusion of Parisi and Lund (2000), relative to the time period 1935-1998.  And in a detailed study of the period 1944-1996, Landsea et al. (1999) found decreasing trends for (1) the total number of hurricanes, (2) the number of intense hurricanes, (3) the annual number of hurricane days, (4) the maximum attained wind speed of all hurricanes averaged over the course of a year, and (5) the highest wind speed associated with the strongest hurricane recorded in each year.  In addition, they determined that the total number of Atlantic hurricanes making landfall in the United States decreased over the extended period of time from 1899 to 1996, and that normalized trends of United States hurricane damage between 1925 and 1996 reveal such damage to be decreasing at a rate of 728 million dollars per decade.

A number of other studies confirm and augment these findings about Atlantic hurricane activity over the past century or so.  In studying the characteristics of all recorded landfalling U.S. Gulf Coast hurricanes from 1896 to 1995, for example, Bove et al. (1998) learned that the first half of that hundred-year period experienced considerably more hurricanes than did the last half (11.8 per decade vs. 9.4 per decade), as was also the case for intense hurricanes of category 3 on the Saffir-Simpson storm scale (4.8 vs. 3.6).  In fact, their research showed that the numbers of all hurricanes and the numbers of intense hurricanes have both been trending downward since 1966, with the decade beginning in 1986 exhibiting the fewest intense hurricanes of the entire century, leading them to conclude that "fears of increased hurricane activity in the Gulf of Mexico are premature."

There was, however, a very robust Atlantic hurricane season in 1995; but Landsea et al. (1998) report that average tropical storm and hurricane activity over the Atlantic basin during the preceding four years was the lowest since the keeping of reliable records began, and that in spite of the 1995 spike, "Atlantic hurricane activity has actually decreased significantly in both frequency of intense hurricanes and mean intensity of all named storms over the past few decades," specifically noting that "this holds true even with the inclusion of 1995's Atlantic hurricane season."

Most recently, Elsner et al. (2004) conducted a changepoint analysis of time series of major North Atlantic and U.S. annual hurricane counts for the 20th century, which technique, in their words, "quantitatively identifies temporal shifts in the mean value of the observations."  They discovered that "major North Atlantic hurricanes have become more frequent since 1995," but at "a level reminiscent of the 1940s and 1950s."  In actuality, however, they are not quite at that level yet, nor have they maintained it for as long a time.  Their data indicate, for example, that the mean annual hurricane count for the 7-year period 1995-2001 was 3.86, while the mean count for the 14-year period 1948-1961 was 4.14.  They also report that "twentieth-century U.S. hurricane activity shows no abrupt shifts," noting, however, that there was an exception over Florida, "where activity decreased during the early 1950s and again during the late 1960s."

In a somewhat different type of study, Balling and Cerveny (2003) constructed a database of all tropical storms that occurred within the Caribbean Sea, the Gulf of Mexico and the western North Atlantic Ocean over the period 1950-2002.  This program generated "a variety of parameters dealing with duration, timing, and location of storm season," which they tested for trends, as well as for associations that might exist between these variables and changes in regional, hemispheric and global temperatures.  Their efforts, however, proved futile, for they found "no trends related to timing and duration of the hurricane season and geographic position of storms" in these regions.  Likewise, they say they could find no associations between any of these variables and either local, hemispheric or global temperature.

Last of all, noting that "increases in hurricane intensity are expected to result from increases in sea surface temperature [SST] and decreases in tropopause-level temperature accompanying greenhouse warming," as per climate model predictions and climate-alarmist claims, Free et al. (2004) calculated increases in hurricane potential intensity [PI] from thermodynamic principles based on radiosonde and sea surface temperature data from fourteen island radiosonde stations in the tropical Atlantic and Pacific Oceans, after which they compared their results with those of Bister and Emanuel (2002) at grid points near the selected stations.  This effort, however, yielded "no significant trend in potential intensity from 1980 to 1995 and no consistent trend from 1975 to 1995."  What is more, they report that between 1975 and 1980, "while SSTs rose, PI decreased, illustrating the hazards of predicting changes in hurricane intensity from projected SST changes alone."

Clearly, there would appear to be little question that global warming in the past has tended to reduce both the frequency and intensity of Atlantic basin hurricanes, as these many real-world studies spanning decades to millennia convincingly demonstrate.  Consequently, if the temperature of the planet rises further in the future, we may expect that these trends will likely continue.  Nevertheless, most climate alarmists and some scientists (see our Editorials of 24 Apr 2002 and 1 May 2002) continue to blindly contest this conclusion.

References
Balling Jr., R.C. and Cerveny, R.S.  2003.  Analysis of the duration, seasonal timing, and location of North Atlantic tropical cyclones: 1950-2002.  Geophysical Research Letters 30: 10.1029/2003GL018404.

Bister, M. and Emanuel, K.  2002.  Low frequency variability of tropical cyclone potential intensity.  1. Interannual to interdecadal variability.  Journal of Geophysical Research 107: 10.1029/2001JD000776.

Boose, E.R., Chamberlin, K.E. and Foster, D.R.  2001.  Landscape and regional impacts of hurricanes in New England.  Ecological Monographs 71: 27-48.

Bove, M.C., Zierden, D.F. and O'Brien, J.J.  1998.  Are gulf landfalling hurricanes getting stronger?  Bulletin of the American Meteorological Society 79: 1327-1328.

Easterling, D.R., Evans, J.L., Groisman, P.Ya., Karl, T.R., Kunkel, K.E. and Ambenje, P.  2000.  Observed variability and trends in extreme climate events: A brief review.  Bulletin of the American Meteorological Society 81: 417-425.

Elsner, J.B., Liu, K.-b. and Kocher, B.  2000.  Spatial variations in major U.S. hurricane activity: Statistics and a physical mechanism.  Journal of Climate 13: 2293-2305.

Elsner, J.B., Niu, X. and Jagger, T.H.  2004.  Detecting shifts in hurricane rates using a Markov Chain Monte Carlo approach.  Journal of Climate 17: 2652-2666.

Free, M., Bister, M. and Emanuel, K.  2004.  Potential intensity of tropical cyclones: Comparison of results from radiosonde and reanalysis data.  Journal of Climate 17: 1722-1727.

Landsea, C.W, Bell, G.D., Gray, W.M. and Goldenberg, S.B.  1998.  The extremely active 1995 Atlantic hurricane season: environmental conditions and verification of seasonal forecasts.  Monthly Weather Review 126: 1174-1193.

Landsea, C.N., Pielke Jr., R.A., Mestas-Nuñez, A.M. and Knaff, J.A.  1999.  Atlantic basin hurricanes: indices of climatic changes.  Climatic Change 42: 89-129.

Liu, K.-b. and Fearn, M.L.  1993.  Lake-sediment record of late Holocene hurricane activities from coastal Alabama.  Geology 21: 793-796.

Liu, K.-b. and Fearn, M.L.  2000.  Reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern Florida from lake sediment records.  Quaternary Research 54: 238-245.

Parisi, F. and Lund, R.  2000.  Seasonality and return periods of landfalling Atlantic basin hurricanes.  Australian & New Zealand Journal of Statistics 42: 271-282.