Paul Homewood at ‘Not A Lot of People Know that‘
Last May the Miami Herald story quoted below was being widely covered
The statistician William Briggs has published a rebuttal on his website this week, which was written by Greg Kent and attacked the statistical basis of the Kossin study. You can read it here.
The study looks at the period 1979 to 2017, and compares 1979-1997 with 1998-2017
In mid-May 2020, the Proceedings of the National Academy of Sciences (PNAS) published an article on hurricane trends over the past 39 years. That study, Kossin et al 2020, found “a clear shift toward greater intensity” storms that is manifested in the observational record as “increased probabilities of exceeding major hurricane intensity.”
Both theory and climate models have long projected a shift to a higher proportion of high intensity storms but support for this theory has been difficult to detect in the observational record. Kossin et al 2020 provided a new homogenized dataset of hurricane wind intensity estimates for global tropical cyclones from 1979-2017.
Based on this new dataset, the article claimed that a statistically significant shift to more intense storms has finally been detected in the observational record. By identifying “significant global trends in [tropical cyclone] intensity over the past four decades,” as projected by the models, the paper’s findings were said to “increase confidence in projections of increased [tropical cyclone] intensity under continued warming.”
The mainstream media trumpeted the results of this new study to a broader audience. The New York Times stated that “Climate Change Is Making Hurricanes Stronger.” Similarly, the Miami Herald urged south Floridians to “Expect stronger, deadlier, more frequent hurricanes in the years to come.” The Washington Post headline claimed that “The strongest, most dangerous hurricanes are now far more likely because of climate change.”
As if the headline wasn’t scary enough, the Post’s article warned the public: “With powerful hurricanes on the increase, one can expect damage costs, in dollar terms and in potential loss of life, to skyrocket.” The lead author of the study, Dr. James Kossin, told the Post that “we have high confidence that there is a human fingerprint on these changes.” All of this was quite worrisome news, coming as it did just before hurricane season started.
Kent makes one crucial observation, without realising its true significance:
The pervasive erroneous calculations in the original paper and the invalid claim of statistical significance are not the only issues with Kossin et al. There is also reason to question whether the 10% increase in the proportion of major hurricane force winds was a global or largely regional phenomenon. Kossin et al presented results for each of the hurricane basins around the world. The data shows that the global results are driven largely by a single basin, the North Atlantic. The proportion of major wind speeds increased by 72% in the North Atlantic, far more than in any other hurricane basin. Western Pacific, which accounts for over 40% of the major hurricane force winds over the last 4 decades, showed a smaller proportion of intense storms in the later period (indicating a negative change). The other basins either showed no change at all between periods or the change was so small as to fail tests of statistical significance at traditional levels of confidence.
There is actually a very good reason why there have been more intense hurricanes since 1998 than before – the Atlantic Multidecadal Oscillation or AMO. Here’s what NASA have to say about the AMO:
The AMO was in cold phase between 1979 and 1995, and has been warm ever since. So the increase in hurricane intensity has nothing whatsoever to do with “climate change”, and instead is a consequence of natural ocean cycles.
In any other field of science, peer review would have spotted this fatal flaw in Kossin’s paper, which would never have been published.
THE ORIGINAL MIAMI HERALD ARTICLE:
Stronger, deadlier and more frequent — that’s the trend scientists at the National Oceanic and Atmospheric Administration (NOAA) have seen in the past few decades, and they expect that trend to continue in the years to come, according to a new study.
Researchers at the University of Wisconsin and NOAA analyzed satellite data of tropical cyclones over the last 40 years and found category 3, 4 and 5 hurricanes were becoming increasingly common, CNN reported. Decade after decade, the likelihood of major global storms has increased, according to CNN.
“The change is about 8% per decade. In other words, during its lifetime, a hurricane is 8% more likely to be a major hurricane in this decade compared to the last decade,” James Kossin, author of the study, told CNN.