Back in September 2014, a climate skeptic named Bob Tisdale posted a criticism of a scientific study by Kuffner and others that compared the recent temperatures at some Florida coral reefs with temperatures from over 100 years ago. The blogger at the HotWhopper web site, who goes by the pseudonym of Sou, responded to Tisdale’s blog post with one of her own. She pointed out many errors and misunderstandings. Tisdale in return posted an “open letter” to Miriam, which is Sou’s real name. His open letter addressed mostly Sou’s criticism of some earlier Tisdale blog posts, but he mentioned the coral reef temperature argument also.
So here we have both sides of an argument on climate change. Let’s take a look at what the different parties say and see who has valid points.
Tisdale has two main criticisms. One, he pointedly complains about Kuffner’s choice of focusing on two separate periods, one from around the turn of the twentieth century and one from around the turn of the twenty-first century. Tisdale asks “What happened to the sea surface temperatures in that region between the turns of the 20th and 21st Centuries?” and “Could they simply have cherry-picked two time periods—per lighthouse—so they could make alarmist claims about coral reefs?”
In response, Sou points out that there were clear reasons for Kuffner’s analysis of data from two separate periods. There were in fact no in situ temperature readings for the years between the two periods, and Kuffner was interested in examining the actual temperatures at the coral reef sites. Sou summarizes by saying, “it seems to me that direct measurements taken right on the reefs, and below the surface, would be much more relevant to this particular research.”
When we look at the actual paper by Kuffner et al., we see that Sou is in the right here. The paper spends almost a third of its length discussing the data. Kuffner also points out the known weaknesses of SST data, especially in a case where in situ data is available and relevant for an understanding of the increasing incidence of coral bleaching in the Florida Keys.
Tisdale’s failure to even mention the stated reasons for using the in situ data shows that Tisdale has no interest in having an honest discussion. If he had, he would have mentioned Kuffner’s reasons and then tried to point out problems with them if he could. Instead, he jumped directly to insinuations of cherry-picking.
Tisdale also claims that when one looks at the change in temperature from HADISST data set for the roughly 110-square-kilometer area around the Florida coral reefs, there is little or no warming trend since 1930. Also, earlier periods had times when the sea surface temperatures reached stressful levels. Because Kuffner said that
“Results indicate that the warming observed in the records between 1878 and 2012 can be fully accounted for by the warming observed in recent decades…. [and t]he magnitude of warming revealed here is similar to that found in other SST datasets from the region and to that observed in global mean surface temperature.
Tisdale complains that “somehow, we’re supposed to believe manmade greenhouse gases are causing harm to the coral in recent years.”
Sou’s response is to point out that looking at the gridded HADISST data set is simply not appropriate when the goal is to look at specific sites where actual thermometer readings are available. She also wonders why Tisdale is so eager to look at the HADISST data set when usually those of his point of view are very critical of data sets that involve averaging, interpolating, and adjusting of the various data sources in order to come up with the final results.
Tisdale clearly wanted Kuffner et al. to more closely consider the HADISST data as well as the in situ data that they had. However, if they had I don’t think the result would have been any different. They would have noted that the coral reefs probably had temperatures aligned with those given for the much larger area around them from HADISST, but we simply don’t know if the actual coral reef temperatures were slightly higher, the same as, or slightly lower than the HADISST temperatures. In addition, simply eyeballing the graphs provided by Tisdale, there is a greater frequency of stressful temperatures in decates. This greater frequency would still be a significant point in favor of saying that global warming in recent decades is contributing to the bleaching of the coral reefs.
Tisdale does little to respond to Sou’s criticism, only referring to her blog post as “mistake-filled” but not pointing out any mistakes. He also criticizes her for treating a commenter rudely who offered corrections. Unfortunately for Tisdale’s side of things, the commenter was not so much offering corrections as being obtuse. The argument is basically over the nature of the HADISST data set. Sou and other commenters point out that the HADISST data set is irrelevant when you have in situ temperature data that you can use and when, as in Kuffner’s case, you want to look at what is happening specifically at the sites where the temperatures were taken. The commenter on Tisdale’s side keeps asking why Tisdale’s data is wrong, and then goes on to argue about what sea-surface temperature means. The commenter claims that because the HADISST data is based not just on satellite data of the thin skin of the sea, but also uses temperature data from ships, buoys, and so on, that data set not really just of the thin skin of the sea as opposed to temperatures at the depth of the coral reefs. This argument is a red herring. It doesn’t matter if the HADISST is meant to measure the temperatures at the depth of the coral reefs or at the very surface of the sea. If you have in situ data and you are examining what is happening at specific sites, then the in situ data is superior. The HADISST, because it is averaged and adjusted from many types of data and across a large area, will be inferior.
The commenter also sides with Tisdale in the matter of what accounts for the rise in temperatures between Kuffner’s two data sets. Tisdale believes Kuffner cannot attribute the rise in temperature in the coral reefs from the turn of the 20th century to the turn of the 21st century to global warming (or, as Tisdale phrases it, “manmade greenhouse gases”) because HADISST data shows no warming the 30’s. Yet one can easily quibble with Tisdale in several ways. First, as a couple of commenters on the HotWhopper site pointed out, by using other data sets, one can see an upward trend since the 30’s. Second, it’s not true that there was no warming since the 30’s. It’s not the case that temperatures reached a high point then and stayed there until the present. Rather, there was a cooling period and then a more rapid increase. Third, there is an increase in the frequency of stressful temperatures in the recent period. Tisdale conveniently does not notice this. Finally, when Tisdale speaks of the warming occurring in the first half of the 20th century and reaching a peak in the 30’s or early 40’s, it’s quite clear that he assumes global warming is not involved, yet it is quite reasonable to assume that the increased CO2 already present then was having some effect.
Tisdale comes across as someone who puts all his energy into finding evidence that seems to support the view he already has. If he had been interested in contributing to the scientific understanding of the recent increase in coral bleaching in the Florida Keys, he would have taken a very different approach. He would have had to argue much more carefully how using HADISST data would have helped. However, his interest was clearly in attacking a view he disliked. He did not want to take the extra effort to consider the strengths AND the weaknesses of the HADISST data.
References:
Kuffner et al.:
http://link.springer.com/article/10.1007/s12237-014-9875-5/fulltext.html
Tisdale (archived)
https://archive.today/z5Rng#selection-831.2-831.271
HotWhopper
http://blog.hotwhopper.com/2014/09/perennially-puzzled-bob-tisdale-surfs.html
Comment thread at HotWhopper:
http://blog.hotwhopper.com/2014/09/perennially-puzzled-bob-tisdale-surfs.html?showComment=1410536036510#c1825756406718567549
