...Climate change theorists assert that warming ocean temperatures are increasing the number and strength of hurricanes that form and make landfall in the United States....
...Looking at the historical data, one does not find a startling increase in hurricane activity in recent decades, and only modest evidence to suggest that hurricanes in the Atlantic basin are increasing either in number or severity....
...The National Hurricane Center, a division of the National Weather Service, has compiled reliable information on hurricanes going back to the middle of the nineteenth century—though the information the nhc collects has grown much more reliable in recent decades with the development of satellite imagery and ever-more sensitive instruments with which to measure the strength and windspeeds of hurricanes. There is no shortage of information to test the claims about increasing hurricane activity.
1 Are hurricanes in the Atlantic Ocean increasing in frequency with the passage of time?
The Hurricane Research Division (hrd) of the National Ocean & Atmospheric Administration has tabulated the annual number of Atlantic hurricanes going back to 1851....the averages look like this:
1950-59: 6.9 per year
1960-69: 6.1 per year
1970-79: 5.0 per year
1980-89: 5.2 per year
1990-99: 6.4 per year
2000-09: 7.4 per year
2010-18: 7.0 per year
2 Are more hurricanes making landfall in the United States with the passage of time?
The hrd maintains an accurate list of hurricanes making landfall in the United States going back to 1851 and running through 2018.... Below is the decade-by-decade enumeration going back to 1950:
1950-59: 18 hurricanes made landfall
1960-69: 15 hurricanes made landfall
1970-79: 12 hurricanes made landfall
1980-89: 16 hurricanes made landfall
1990-99: 14 hurricanes made landfall
2000-09: 19 hurricanes made landfall
2010-18: 11 hurricanes made landfall
Average by decade, 1950 to 2018: 15
Average by decade, 1990-2018: 15
Average by decade, 1950-1989: 15
3 Are Atlantic hurricanes growing more powerful with the passage of time?
Over the hundred-seventy-year period, just four Category 5 hurricanes (the most powerful of all storms) have made landfall in the United States: The Labor Day hurricane that hit the Florida Keys in 1935; Hurricane Camille, which hit the Gulf coast in 1969; Hurricane Andrew, which hit south Florida in 1992; and Hurricane Michael, which hit Florida and Georgia in 2018. These events appear unrelated to changes in ocean temperatures....
The decade-by-decade pattern looks like this:
1950-59: 3.9 major hurricanes per year (Category 3, 4, and 5)
1960-69: 2.8 major hurricanes per year
1970-79: 1.6 major hurricanes per year
1980-89: 1.7 major hurricanes per year
1990-99: 2.5 major hurricanes per year
2000-09: 3.6 major hurricanes per year
2010-18: 2.9 major hurricanes per year
Average by decade, 1950-2018: 2.7 per year
Average by decade, 1950-1969: 3.3 per year
Average by decade, 1970-1989: 1.7 per year
Average by decade, 1990-2018: 3.0 per year
...How, then, in view of these data, should we assess the claims that Atlantic hurricanes are increasing in numbers and strength in recent decades in response to rising atmospheric and ocean temperatures, and are also making landfall at increasing rates?
There has been a modest increase in the frequency of Atlantic hurricanes in recent decades along with a slight increase in their strength from year to year, but no increase in the number of hurricanes making landfall in the United States and no increase since 1950 in the number of the most powerful hurricanes (Category 4 and 5 storms) to hit the U.S. mainland. Moreover, any trend that we find in the frequency and strength of hurricanes in the past few decades is mostly washed out when we compare those rates to the ones experienced in the 1950s and 1960s. This suggests that the frequency and strength, though perhaps increasing of late, are but loosely related to recent measured increases in Atlantic Ocean temperatures.