Hurricane Frequency Is Not Increasing

I was glued to the weather channel this past weekend to watch Hurricane Henri  head for New England, but was relieved when Henri was downgraded to a tropical storm. I have read and heard the climate change is responsible for increasing hurricane intensity and frequency.  Satellite data from the last 40-45 years is the source of that belief. Over the weekend I had plenty of time to read up on the latest research. What I found is that according to an article published recently in Nature Communications that may not be true.

In the article, “Changes in Atlantic major hurricanefrequency since the late-19th century,” that I have cited below, Dr. Gabriel Vecchi a climate scientist from Princeton University, found that the frequency  of hurricanes has not increased in the Atlantic over the past 168 years. The trend in intensity was not examined, though the data brings into question if the intensity of storms has increased over the 168 year period.

The scientists found: “that recorded century-scale increases in Atlantic hurricane and major hurricane frequency, and associated decrease in USA hurricanes strike fraction, are consistent with changes in observing practices and not likely a true climate trend.” The scientists developed a method using probabilities and known storm tracks to adjust the old observation data and found no change in hurricane intensity and frequency over 1851-2019. Instead, they found a decrease in hurricane frequency about 50 years ago and a recovery.

Even though the North Atlantic (NA) basin is a minor contributor to global cyclone storm frequency, Atlantic hurricanes have a well documented long-term records of their track and frequency mostly because of the damage the storms bring when they make landfall as Categories 3–5.  

In homogenizing the historical data from 1851–2019 the scientists discovered that the increases in basin-wide hurricane and major hurricane activity since the 1970s was not a trend caused by climate change, but a recovery from a deep minimum in the 1960s–1980s. This same recovery may have impacted the conclusions from other studies done on storm intensity in the 1979-2019 period.

The scientists postulated that air pollution containing particulates blocked and scattered sunlight and induced reductions in major hurricane frequency. They go on to say that this could have masked a century-scale greenhouse-gas warming contributions to North Atlantic major hurricane frequency. Meanwhile, it is not in their data.

The accepted climate models and theoretical arguments indicate that in a warming world the hurricane peak intensity and intensification rate should increase, along with frequency. So, climate models currently increase the overall number of Categories (3, 4, or 5) hurricanes in response to CO2 increases.

The scientists do not believe that their work provides evidence against the hypothesis that greenhouse-gas-induced warming may lead to an intensification of North Atlantic hurricanes. Kossin et al. in their work using satellite data for the period of 1979-2017 found a statistically significant upward trend in the intensity of hurricanes and tropical cyclones globally. The new study may bring that finding into question, but it is argued that substantial variability may obscure trends computed over the past century, and pollutant-driven reduction in hurricane activity over the 1960s–1980s may have obscured any greenhouse induced hurricane intensification over the 20th century.

Other research has supported the idea that the number of hurricanes has not increased, but there is a strong belief amongst climate scientists that storm intensity is increasing, though there is no documentation of that as yet. Data selection period and the difficulty of collecting accurate data in the past has limited the ability to see if the trends exist clearly.

Dr. Vecchi and his research team are the go-to researchers on climate impacts on hurricanes and extreme weather events. This is one of those instances when time and further data collection will ultimately hold more answers or at least information. In the meantime, remember that storms can be deadly, rising sea level increases storm surge and flooding; and we should always take storm warning seriously.

Vecchi, G.A., Landsea, C., Zhang, W. et al. Changes in Atlantic major hurricane frequency since the late-19th century. Nat Commun 12, 4054 (2021). https://doi.org/10.10 38/s41467-021-24268-5