What was done
The authors used data for annual U.S. hurricane numbers obtained from the U.S. National Oceanic and Atmospheric Administration and data for average sea surface temperature (SST) anomalies for the region bounded by 6°N to 6°S latitude and 90°W to 180°W longitude (called the "cold tongue index" or CTI) obtained from the Joint Institute for the Study of the Atmosphere and the Oceans to see if there is a connection between the number of hurricanes that hit the eastern coast of the United States each year and the presence or absence of El Niņo conditions.

What was learned
Based on data for the period 1901-2000, the authors concluded that "when CTI values indicate below normal equatorial SSTs, the probability of a U.S. hurricane increases."  Or as they describe the relationship in another place, "the annual count of hurricanes is higher when values of the CTI are lower (La Niņa events)."  In addition, they determined that the North Atlantic Oscillation is "an additional important factor in explaining U.S. hurricane activity on the decadal scale after accounting for ENSO."

What it means
Climate alarmists typically claim that global warming will result in more frequent and stronger El Niņos; and they say that this phenomenon will result in more frequent and stronger hurricanes.  The past century of real-world hurricane experience for the United States, however, suggests just the opposite, as the yearly number of U.S. land-falling hurricanes has generally tended to decrease during El Niņo conditions, as has the overall occurrence of hurricanes in the entire Atlantic basin.