It’s hurricane season but fortunately it’s winding down just to give way to the equally dreadful artic blasts of winter. During the summer season of excess wind, one’s thoughts, for the curious anyway, inevitably lead to queries, theories, or low proof opinions attempting to understand the causality, if any, between the frequency and strength of hurricanes with climate change or global warming. These are perfectly sensible and logical thoughts along with the subsequent questions, such as: Are hurricanes increasing in frequency due to climate change? Are hurricanes increasing in strength due to climate change?
These are valid questions, but likely a more germane question, or three, may be: If climate change is occurring what would the expected outcome be for the frequency and strength of hurricanes? Increasing? Decreasing? Something else? Are human gas inputs into the planet’s atmosphere causally linked to its energy budget? What methods and processes would one employ to answer these questions?
If you thought, I was going to attempt to answer the questions posed above you would certainly be wrong. I do not have the training or knowledge to provide even a precursory opinion, much less a tested and critiqued theory, but I do know how to analyze data and dagnabit I’m going to do just that.
The data used in the analysis below comes from NOAA for the years 1851 through 2021. The data are for hurricane strength only storms, category 1-5, that made landfall over the Atlantic Basin lower 48 states: specifically, the coastal states from Texas to Maine. Excluded from the analysis are all the named Atlantic Basin storms that formed but did not make landfall. Satellites, beginning in the 1960s, are able to observe and track all hurricanes whether they make landfall or not. The satellites have detected considerably more hurricanes developing in the Atlantic Basin than past data, based on storm landfall, suggested. There is a strong link between the recent increase in hurricane strength and frequency due increased observational capabilities rather than anthropogenic origins contributing to climate change.
The graph above plots wind speed in mph versus year of formation for Atlantic Basin hurricanes making landfall along the lower US 48. Years with no hurricanes making landfall are excluded but they account for about 20% of the analyzed interval. The basic analysis of the data shows that for the chosen years, 1851-2021, the average hurricane at landfall is a category 2 storm with an average speed of 100 mph. The trend line shows that the strength of landfall hurricanes has not appreciable changed over the last 170 years: slope of the trend line is 0.0077 or among friends can be taken as 0.
The graph above is the same as the first one shown except, I have attempted to account for the years with no hurricanes making landfall. I accounted for the years of no landfall by setting those data points to 0 mph. I am not comfortable with this approach but ignoring 20% of the data isn’t correct either. The analysis of the data is not significantly different from the previous graph. The average hurricane speed at landfall has decreased to 91 mph from 100 before with the average category being 2. 91 mph is a category 1 hurricane so the average category should be 1 but this is just a rounding up error. Slope of the trend line is again near 0.
The frequency of landfall hurricanes also shows little variation over time. The average number of hurricanes is 1.86 per year with the maximum number of 11 hurricanes occurring in 1917. The gaps in the x-axis are the years with no hurricanes.
The NOAA hurricane data presents a picture of little to no variation in hurricane strength or frequency from 1851-2021. What this says about climate change or global warmer is indeterminant. The question asked above about what changes are expected in hurricane frequency and strength if climate change is occurring needs answering before hurricane variability can be linked to it as a known outcome or consequence.