Holland and Webster stated the following:
Figure 1 shows a strong statistically significant trend since the 1970s similar to that found by Hoyos et al. (2006) and Curry et al. (2006.)
I’ve replicated the hurricane part of their Figure and included 2006 data as they should have – it’s amazes me that authors don’t make the effort to have up-to-date data. Here are some comments.
First, here is Figure 1 of Holland and Webster. They provide no statistical evidence that the trend is “statistically significant”, much less whether is a “strong statistically significant trend”. Is it possible that the apparent trend is simply chance? You’d think that the authors would attempt to show some statistical evidence, but I haven’t been able to locate any in the article. It may be “statistically significant”, but no evidence is provided.
I’ve been able to pretty much replicate the above graph from my collation of hurricane data through to 2006 as shown below – together with 2006 values inexcusably omitted by Holland and Webster.
Figure 2: My emulation of Holland and Webster Figure 1.
Now if this trend were “statistically significant” as claimed by the authors, then one would expect the “trend” to be discernable in the subset from 1986-2006 in the total of all basins. The figure below shows my calculations through to the end of 1986.
Figure 3: Total over all basins. Smoothed using gaussian 9-point smooth with padded mean.