What was done
The authors conducted a "changepoint analysis" of time series of annual major North Atlantic hurricane counts and annual major U.S. hurricane counts for the 20th century, which technique, in their words, "quantitatively identifies temporal shifts in the mean value of the observations."

What was learned
Elsner et al. report 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, "in general, 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."  Last of all, they found that "El Niņo events tend to suppress hurricane activity along the entire coast with the most pronounced effects over Florida."

What it means
In contradiction of the climate-alarmist claim that global warming leads to more intense hurricane activity, the results of this study clearly suggest otherwise.  Not only did North Atlantic hurricane activity not increase over the entire 20th century, during which period climate alarmists say the earth experienced a temperature increase that was unprecedented over perhaps the past two millennia, hurricane activity also did not increase in response to the more sporadic warming associated with periodic El Niņo conditions.  In fact, it decreased.