Category Archives: Temperature Reconstructions

My Conspiratorial Thinking

The tweet which led to my last post also led to an exchange on Twitter which I found somewhat peculiar as it involved things like being told I was promoting conspiratorial nonsense. Despite my best efforts, I was unable to find out what this nonsense was, and alas, it appears we may never know what conspiracy theories I have been espousing.

That mystery aside, the exchange allowed me to state why I think people deriding the pursuit of e-mails from climate scientist via legal means like Freedom of Information requests are in the wrong. It's not that I care about the e-mails themselves. I don't. However:

There has been a long history of climate scientists involved in the global warming debate refusing to share information/data. One of the most famous examples was when climate scientist Phil JOnes responded to a person asking for data by saying:

We have 25 or so years invested in the work. Why should I make the data available to you, when your aim is to try and find something wrong with it.

This sort of reaction is not limited to climate science. Examples of it have been discussed in many fields. I think it's silly. If you're a scientist who believes in his/her work, you should have no problem with people examining it. Refusing to share information/data with people, especially because of perceived traits you believe that person has, is completely unscientific.

When scientists behave in such an unscientific manner, I see no problem with people trying to get access to information they were denied in other ways, such as using the legal system. I don't think that's a remarkable view, but my tweet above led to this response:

I think that question is silly as it seems it should be easy to see at least some examples of what i referred to. If a person publishes a paper and refuses to archive the data used in it, the lack of such an archive can often be apparent. If an author of a paper fails to describe steps they took in their analysis, that can often be apparent. So forth and so on.

That said, the person I was exchanging these tweets asked me to state what data I cannot find several times so I offered to write a post highlighting some examples. What comes next will be a list of just a few examples of data and/or information I have wanted to examine but been unable to because researchers refuse to share it.
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Upside Down Proxies in the IPCC AR5

A recent tweet:

Led me to yet another one of those articles which likes to pretend critics of the (in)famous Hockey Stick are just obsessed with one study published twenty years ago, hoping if they can prove it was fraudulent, something, something, something despite all the later work confirming the Hockey Stick was right.

That, of course, is complete drivel. Critics of the Hockey Stick have long criticized many temperature reconstructions and argued the later ones do not validate the original Hockey Stick. In fact, a common point many people have made is that the later work which supposedly confirms the original often uses data from the original. In fact, many later studies took output from the original one and used it as input for their analysis.

(It turns out if you use the results of a study in your calculations, your calculations may well match those of the original study. Who knew?)

Anyway, that's not what I wanted to look at today. That bugs me, but the article made me look at something which I hadn't thought about in some time. When I did a little digging into it, I discovered there was information I had never seen before. It's somewhat interesting.
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Splicing, Right or Wrong

An issue I discussed in my recent eBook is how Mark Steyn, widely admired figure within the Skeptic community, claims Michael Mann spliced instrumental temperature records onto his (in)famous hockeystick to cover up the fact proxy temperatures (estimated from things like tree rings) were going down. I discussed this because that claim is entirely false.

However, that Mann did not do this does not mean other people have not done it. I was recently surprised to see it is, in fact, an accepted practice within the paleoclimate community these days. This surprised me because years back when a user said:

Whatever the reason for the divergence, it would seem to suggest that the practice of grafting the thermometer record onto a proxy temperature record – as I believe was done in the case of the ‘hockey stick’ – is dubious to say the least.

Apparently holding the same incorrect belief as Steyn (misinformation tends to spread when nobody corrects errors like Steyn's), Mann responded:

No researchers in this field have ever, to our knowledge, "grafted the thermometer record onto" any reconstruction. It is somewhat disappointing to find this specious claim (which we usually find originating from industry-funded climate disinformation websites) appearing in this forum.

Mann said this in late 2004 so I can't fault him for being unaware of what would happen after 2010, but given the response Mann shows to this accusation, I find it strange this practice would be an accepted one a mere ten years later. Plus, I thought it was interesting nobody has pointed out any recent examples of it happening despite at least one being easy to find.
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Precise Paleoclimatology

Readers familiar with my writings will be familiar with the idea of paleoclimatology. It's basically a study of climate over long periods of time. It gives rise to reconstructions of temperatures, precipitation and various other factors over hundreds, thousands or even tens of thousands of years.

I'm not impressed by the field as a whole. I think there is a lot of good work done in it, but I also think a lot of bad work has been allowed to tarnish the field and skew its conclusions. That's not important for today's post though. Today, I just want to show people the most precise estimates I've seen of temperatures nearly two hundred centuries past. I came across them because of a tweet:


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Failure to Replicate

Things went well yesterday, but the painkillers are making my head a little fuzzy. As such, I figured it'd be a good time to write up something I probably should have written up a while back. You see, over a month ago Steve McIntyre wrote this about the recent Gergis et al paper:

Gergis et al 2016 stated that they screened proxies according to significance of the correlation to local gridcell temperature. Law Dome d18O not only had a significant correlation to local temperature, but had a higher t-statistic (and correlation) to local instrumental temperature than:
24 of the 28 proxies retained by Gergis in her screened network;
either of the other two long proxies (Mt Read, Oroko Swamp tree ring chronologies);
Nonetheless, the Law Dome d18O series was excluded from the Gergis et al network. Gergis effected her exclusion of Law Dome not because of deficient temperature correlation, but through an additional arbitrary screening criterion, which excluded Law Dome d18O, but no other proxy in the screened network.

This was a serious accusation he and I had actually discussed in e-mails before he wrote that post. As I told him in those e-mails, I couldn't find a way to replicate his results. I asked him to confirm the data he was using matched what I was using, but that didn't happen. When he wrote the post, I asked again. I asked again later via e-mail, again without success.

Mind you, McIntyre never said, "No," and I think he does intend to do this eventually. I tried to be patient, but given the seriousness of McIntyre's accusations and how they appear to be completely wrong, I think waiting over a month is more than sufficient.
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Odd Situation in Gergis et al

I've owed you guys another post about the recent Gergis et al paper for a little while now. I've been held back by losing all my code written to examine to a power outage, and I'm going to be out of town for the weekend. Fortunately, there is an interesting issue I can write about today. It came to my attention due to the blogger Anders writing this comment at his site:

Hope this doesn’t the “clean exit”, but I thought I would post this figure from Gergis et als SI. It compares the main reconstruction (black) with one in which there was no screening and all 51 proxies were used (red dash) and one with no screening and using all the 36 proxies in the reconstruction domain (green dot). Doesn’t appear to be wild differences, but am not sure how the non-screening reonstructions would influence the 2SE.

I had seen this figure before, but I've been hung up on trying to replicate screening results for the paper (as well as Steve McIntyre's stated results for it) so I hadn't paid much attention to it. Anders drawing my attention to it led me down a windy and strange path.
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Gergis et al, (Again) Failing to Do What They Claim

Readers familiar with the 2012 Gergis et al paper will likely remember the paper was withdrawn after it had been accepted for publication (but prior to actually being published) because it turns out the authors did not do what they claimed to have done. Specifically, they claimed to use detrended series for their screening to try to avoid the "screening fallacy" when in reality they hadn't detrended anything. Today I'd like to show the authors have once again failed to do what they claim to have done.

For some background on this issue, there's a good post up at Climate Audit about this paper, and I'm going to try not to rehash the points it covers. There are also two posts I've previously written on the subject, here and here. Being familiar with these posts should be helpful but not necessary as the central problem I want to discuss is really as simple as, "They didn't do what they claim to have done."
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Very Small Differences

As our last post discussed, one of the key issues in this whole Gergis et al affair is how one should screen proxies to decide which ones to use and which ones not to use. In 2012, Gergis et al claimed to have screened proxies because:

For predictor selection, both proxy climate and instrumental data were linearly detrended over the 1921–1990 period to avoid inflating the correlation coefficient due to the presence of the global warming signal present in the observed temperature record. Only records that were significantly (p<0.05) correlated with the detrended instrumental target over the 1921–1990 period were selected for analysis.

They wanted to take steps to avoid a problem commonly known as the Screening Fallacy. Of course, as it turned out they hadn't actually detrended their data like they claimed, and if they had, their results would have been very different. This gives rise to an important question, namely, why do they say this in their latest paper:

Our results also show that the differences between using detrended and raw correlations to screen the predictor networks, as well as between using field mean and local correlations, are minor (Figs. S1.3 and S1.4 in the supplemental material). Given this insensitivity, local detrended correlations were used to select our final set of temperature predictors (see theoretical discussion in section S1 in the supplemental material).

According to their newest paper, it makes very little difference whether one detrends or not. They also say it makes little difference whether you use "local" temperatures for correlation testing or temperatures of the region, but I'll discuss that in a little bit. Just understand the quotations marks I place around the word "local" are important.

For now, the main question is how do the authors conclude it doesn't matter whether or not you detrend your data before correlation testing? That's the exact opposite of what they concluded when they were forced to withdraw their 2012 paper.
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The Gergis Saga Continues

As readers likely know, I have long followed The Hockey Stick Debate. It is, in fact, the reason I became interested in the global warming discussion. And while I've written about it a fair amount in the past, to the point of writing two (short) eBooks on the subject, I haven't discussed it much in some time. The reason is simple - the debate has largely died off.

I could go on and on about how climate science has largely abandoned the infamous Hockey Stick, claiming to support it while only publishing results very different from it, but the reality is climate scientists have largely tried to distance themselves from the subject. I suspect they have largely because the problems surrounding the subject became too much for them to bear, meaning a tactical retreat was in order.

Whatever the reason, the point is debates over paleoclimatic reconstructions have died down so much there's been little reason for me to write about them until today. Today, a new story has broken which will be a source of great interest. I came across the news because I saw a link to a news article whose headline says:

How a single word sparked a four-year saga of climate fact-checking and blog backlash

This caught my eye for a variety of reasons, including my interest in the rise in "fact-checking" by the media (which often isn't really fact-checking). Naturally, I clicked on it. I never anticipated it'd be about a subject I know well, a 2012 paper by Joelle Gergis and co-authors.
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Proof Adjustments Don't Exaggerate GW, They Just Exaggerate AGW

The Intergovernmental Panel on Climate Change said this in its summary (for policymakers) of its latest major report:

It is extremely likely (>95% confidence) that human influence has been the dominant cause of the observed warming since the mid-20th century.

This report, the Fifth Assessment Report, was preceded by one whose summary said:

Most of the observed increase in global average temperatures since the mid-20th century is very likely (>90% confidence) due to the observed increase in anthropogenic greenhouse gases.

Both reports also discuss the total amount of warming observed since the nineteenth century, but as these quotes show, a key issue in the global warming discussion is what portion of the warming since 1950 has been caused by human influences on the planet's climate. Some people would say 0%. Others would say what the IPCC has said in the past, that it is 50+%. Others would say it is over 100%. I think that last one is nonsensical, but that's a topic for another post.

What's most important, however, is there's a group of people who say the answer is influenced by the "fact" human adjustments to the temperature record have artificially exaggerated the amount of warming that has actually occurred. They may think the exaggeration is slight, or they might think it is so large as to completely fabricate the apparent warming trend. Imagine telling them things like:

Wouldn't that seem a little off? If a person's concern is adjustments to data which exaggerate warming, would you think telling them what adjustments do since ~1900 would address their concerns in a clear and convincing manner? I don't think so. I think a lot of people might well look at the IPCC attribution statements and focus on the period after 1950, where the human contribution is said to be the major factor. That's why I told that user, Robert Way:


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