What was done
The authors calculated return periods of Atlantic-basin U.S. landfalling hurricanes based on "historical data from the 1900 to 2006 period via extreme value methods and Poisson regression techniques" for each of the categories (1-5) of the Saffir-Simpson Hurricane Scale, which are defined by wind speeds of (1) 74-95 mph or 119-153 km/hr, (2) 96-110 mph or 154-177 km/hr, (3) 111-130 mph or 178-209 km/hr, (4) 131-155 mph or 210-249 km/hr, and (5) greater than 155 mph or 249 km/hr.

What was learned
Return periods (in years) for Atlantic-basin U.S. landfalling hurricanes for the five Saffir-Simpson Hurricane Scale categories were: (1) 0.9, (2) 1.3, (3) 2.0, (4) 4.7, and (5) 23.1. In addition, the two researchers report that corresponding non-encounter probabilities in any one hurricane season were calculated to be (1) 0.17, (2) 0.37, (3) 0.55, (4) 0.78, and (5) 0.95. They also state that the hypothesis that U.S. hurricane strike frequencies are "increasing in time" -- which is often stated as fact by climate alarmists -- is "statistically rejected."

What it means
As the world has warmed over the past hundred-plus years, at a rate that climate alarmists typically describe as "unprecedented," there has been no significant increase in the strike frequency of U.S. landfalling hurricanes. Hence, there is substantial reason to believe that if the planet warms any further in the future, the same situation will likely continue to prevail.