Update: Dr. Roger Pielke Jr. says via email “the fake photo is perfectly appropriate” and adds this update to his report on Grinstead from last year:
Today Grinsted et al. have another paper out in PNAS in which they follow up the one discussed below. They make the fantabulous prediction of a Katrina every other year. They say in the new paper:
[W]e have previously demonstrated that the most extreme surge index events can predominantly be attributed to large landfalling hurricanes, and that they are linked to hurricane damage (20). We therefore interpret the surge index as primarily a measure of hurricane surge threat, although we note that other types of extreme weather also generate surges such as hybrid storms and severe winter storms. . .
As I showed in this post, which Grinsted commented on, the surge record does not accurately reflect hurricane incidence or damage. Another poor showing for PNAS in climate science.
Guest Post by Willis Eschenbach
Anthony has commented on the recent paper by Grinsted et al. in his post called “Model predicts more storm surge, but they use what appears to be a fake photo in the press release“. The original study Abstract is here, but the paper has not yet been published. Fortunately, the supplementary material with their summary data is online here. This is the relevant quote from their Abstract (emphasis mine).
We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years (P < 0.02).
Their claim from the abstract is that historically, warmer years have larger storm surges from cyclones … which seemed doubtful to me. So I got their “Surge Index” data from their Supplementary Information, and took a look. Figure 1 shows the results. I have plotted the size of the surge against the temperature anomaly for the month in which the surge occurred.
Figure 1. Surges plotted against the HadCRUT3 temperature anomaly for that month. PHOTO: Wolf Rock Lighthouse
Well … that sure doesn’t show what they claimed. There’s absolutely no trend in that at all. In particular, “Katrina sized events” (storm surge >= 113) are more common and larger in the colder months, not the warmer months. So having failed there, let me try something else …
They talk about warm and cold years, not warm and cold months. I’ll give that one a try. Figure 2 shows the previous Surge Index results compared to the temperature for that year, rather than for the month … or it will as soon as I go calculate, create, and shoot Figure 2 … OK, here it is.
Figure 2. Surges plotted against the HadCRUT3 temperature anomaly for that year.
That didn’t help in the slightest. Again, no trend in storm surge index with respect to temperature. And again, “Katrina sized” events with a storm surge 113 or greater are more common in the colder years.
So I fear that I can’t replicate their results. They may be using some very sophisticated analysis … but in my experience, if a trend were actually present, it would show up in one of the two charts above.
What am I missing?
Regards to everyone,
DATA: Spreadsheet with the values is here.
[UPDATE] A reader points out that the paper is now available here.