Scientists at the National Oceanic and Atmospheric Administration say their analysis of more than a century of Atlantic hurricane data suggests that an apparent increase in the number of storms since the late 19th and early 20th century is the result of better observations and better analysis of the storms as weather science and technology have improved.
The improvements have led to the detection of more short-lived tropical systems that were missed in earlier years, the researchers concluded in a paper published in the American Meteorological
Society's Journal of Climate.
Storms lasting barely a day or two that would have gone unnoticed in past decades are now being picked up by satellites and other data collections systems, and better analytical tools are defining more of them as true tropical systems.
Some examples they cite include Andrea, Chantal (forming south of Nova Scotia in the image at left), Jerry and Melissa, in 2007, and last year's Arthur and Nana.
Although the data do reveal "substantial multi-decadal variability" in the number of tropical storms, the long-term numbers are stable. "The study provides strong evidence that there has been no systematic change in the number of north Atlantic tropical cyclones during the 20th century," said Dr. Brian Soden, a professor at the University of Miami's Rosenstiel School for Marine and Atmospheric Sciences.
The study's authors conclude that their findings are consistent with several recent global warming simulations. They note that while their work found no real increase in Atlantic storm counts, it did not address the argument by some researchers that global warming is increasing the intensity, if not the number of these storms, as well as the number that reach "major" hurricane status each year.