Talk:Divergence problem

Thanks for starting this, guys. I'll contribute a bit as time permits. Cheers, Pete Tillman (talk) 19:50, 18 December 2009 (UTC)

Undue weight and BLP problems
I've removed, for now, the reference to the CRU hacking. This is an article on science, not a gossip column. The context-free quote of a statement by Phil Jones raises serious biographies of living persons (BLP) problems, as the same form of words anywhere else on Wikipedia would. --TS 20:35, 2 January 2010 (UTC)


 * Tony, this is a direct quote from Phil Jones and his university. You're not going to get more authoritative, and less gossipy, than that. Please spell out your BLP concerns more clearly. And this is the most news the divergence problem is ever likely to get, and is of significant encyclopedic & public interest. So the topic certainly meets any WP:Weight concerns. -- Pete Tillman (talk) 19:26, 7 January 2010 (UTC)


 * I've removed it again. This is just... not very sensible. This article is about the *science* of the divergence problem. Why do you feel the need to drag the politics into this article? It adds nothing to our understanding, and just muddies the waters. We already do the politics to death elsewhere. I have a question for you: do you have any interest in the science, and can you point me at your last edit to climate-related science that isn't tinged with politics? William M. Connolley (talk) 19:59, 7 January 2010 (UTC)

Article probation
Please note that, by a decision of the Wikipedia community, this article and others relating to climate change (broadly construed) has been placed under article probation. Editors making disruptive edits may be blocked temporarily from editing the encyclopedia, or subject to other administrative remedies, according to standards that may be higher than elsewhere on Wikipedia. Please see General sanctions/Climate change probation for full information and to review the decision. --TS 20:38, 2 January 2010 (UTC)

Sargasso inappropriate
This is also wrong.


 * Specifically, tree ring data was used to suggest that the current warming is much more than what occurred during the Medieval Warm Period.

Needs citation: who is supposed to have said this. What does "much more" mean?


 * Sorry, I thought that tree rings were the evidence for the Mann hockey stick graph. I would be happy to add a reference. Q Science (talk) 21:16, 7 January 2010 (UTC)


 * Using sediment cores (another temperature proxy), there is evidence that the current CO2 induced warming is significantly less than normal climate variability.

but is then backed up by a ref to just one region (the Sargasso). We *know* already that temperatures vary by region - see the MWP article itself. Nor does the ref support "there is evidence that the current CO2 induced warming is significantly less than normal climate variability" - what it actually says is the very differnent "at least some of the warming since the Little Ice Age appears to be part of a natural oscillation".

William M. Connolley (talk) 20:20, 7 January 2010 (UTC)


 * Maybe Sargasso is a bad example, maybe not. The existing paragraph states that ice cores indicate that the temperature is doing what the IPCC says, and I was just trying to add some balance. The Vostok ice core data for the MWP indicates that it was 1.33C warmer than today, which agrees with the Sargasso value of 1.0C. Therefore, I am not convinced that the Sargasso example is any worse than a Vostok ice core. (Actually, the Vostok dates are a little weird, the high was about 400 years ago in the middle of the Little Ice Age. It also shows strong global warming over the last 2,000 years.)


 * At any rate, my point was that if there is a divergence problem in the present, then perhaps there was also one in the past. If that is even possible, then the Importance of the problem is that it suggests that tree ring proxies are not a valid reason to erase the Medieval Warm Period. The current text simply says that the divergence problem is a non-issue and should be ignored. Sorry, but that is just simply a whitewash. In light of climategate (which you also will not allow to be mentioned here), the divergence indicates the strong possibility of fraud. However, I tried to word my paragraph in a neutral way, simply indicating that more research is necessary. Q Science (talk) 21:16, 7 January 2010 (UTC)


 * [M]y point was that if there is a divergence problem in the present, then perhaps there was also one in the past - yes, perhaps. But you need to find a source that says that, not use sources that address other issues to advance that your point.  Guettarda (talk) 21:25, 7 January 2010 (UTC)
 * I have a rather different take on this. I think it is uncontroversial (the idea that there *might* be a DP in the past - not that it certainly is there). And anyway, the appropriate text already exists: However, the fact that during one period the tree-ring temperature proxy deviates from a more accurate record suggests the possibility that this may have happened in the past, too.... William M. Connolley (talk) 21:39, 7 January 2010 (UTC)


 * But the next sentence suggests that ice cores show that there is no divergence in the past when, in fact, they show the opposite. Q Science (talk) 22:08, 7 January 2010 (UTC)


 * I tried to word my paragraph in a neutral way, simply indicating that more research is necessary You said: "The divergence problem, and the fact that the key IPCC scientists were trying to hide it, clearly indicates that more research is needed".  That's clearly not neutral.  And that last bit is an editorial comment.  Guettarda (talk) 21:28, 7 January 2010 (UTC)


 * Then you say are not a valid reason to erase the Medieval Warm Period - this makes me rather suspicious. No-one is trying to erase the MWP; this is, however, a charge often thrown up by the right-wing blogosphere. What makes you think it is a useful thing to say here? In light of climategate... the divergence indicates the strong possibility of fraud - since there is not even the slightest evidence for this, please don't muddy the waters by mentioning it (unless you have some evidence. Do you?). The existing text says Other palaeo-proxies - for example, ice cores - do not suffer from this effect and to a limited extent suggest that the problem does not occur;. This doesn't say the ice cores are correct, just that they don't suffer from the DP William M. Connolley (talk) 21:36, 7 January 2010 (UTC)


 * No-one is trying to erase the MWP; this is, however, a charge often thrown up by the right-wing blogosphere. - actually, it was Al Gore (in his film) that used Mann's plot to erase and make fun of the Medieval Warm Period. As I understand it, that plot was based on tree rings and, therefore, is an appropriate topic for this page. Since the existence, magnitude, and extent of the MWP is central to determining if changes in CO2 concentration can effect the temperature of the planet, it should be important to everyone trying to understand the underlying science. The fact that the key scientists tried (unsuccessfully) to hide the data should also be of interest. Q Science (talk) 22:08, 7 January 2010 (UTC)
 * What does Al Gore have to do with anything here? (and this issue existed long before Gore made his film). As for "Since the existence, magnitude, and extent of the MWP is central to determining if changes in CO2 concentration can effect the temperature of the planet" that certainly demands a . Who says so? (as a note here, as far as i understand things, If the MWP was warmer, then climate sensitivity by necessity must be higher, and thus expected warming from CO2 will be higher as well - contemplate this a bit). --Kim D. Petersen (talk) 22:13, 7 January 2010 (UTC)


 * Interesting reference
 * Climate models do not include or use any information derived from proxy data. They are not calibrated
 * I don't think I believe that.
 * In other words, if the hockey is wrong, nothing changes in the climate projected for 2100. The projections are as correct or incorrect as if the hockey-stick were right.
 * I would love to hear how you support these quotes. As for the "citation needed", IIRC that is part of the justification in the IPCC documents. Q Science (talk) 22:31, 7 January 2010 (UTC)
 * Yes, it is interesting, thats why i chose Eduardo Zorita on purpose here. You recall incorrectly with regards to the "justification" in the IPCC documents. --Kim D. Petersen (talk) 23:29, 7 January 2010 (UTC)

To quote the IPCC
 * Section 1.3.3 - Identifying human-induced climate change requires two steps. First it must be demonstrated that an observed climate change is unusual in a statistical sense.


 * Section 2.3.1 - To determine whether 20th century warming is unusual, it is essential to place it in the context of longer-term climate variability.


 * Section 2.3.2 - The past 1,000 years are a particularly important time-frame for assessing the background natural variability of the climate for climate change detection.


 * Chapter 12 Executive Summary - New reconstructions of the surface temperature record of the last 1,000 years indicate that the temperature changes over the last 100 years are unlikely to be entirely natural in origin, even taking into account the large uncertainties in palaeo-reconstructions.

So, combined with the use of data that hides the MWP (the hockey stick plot), I think that these quotes capture the general thinking in the IPCC documents. (I am surprised that you needed a reference for this.) As for mentioning Gore, I agree that the issue was known long before his movie. I mentioned him as a counter to WMC's suggestion that only "the right-wing blogosphere" is discussing the MWP. The fact that making a joke of the MWP was a critical point in the movie indicates the importance of determining exactly how warm it was. Q Science (talk) 08:46, 8 January 2010 (UTC)

Naive question
If tree rings no longer correlate to temperature, in the current environment where we have an abundance of evidence, why do we assume that they are correlating in the past, where we have much more limited evidence? For example the title of Briffa's paper is "Trees tell of past climates - but are they speaking less clearly today?" - essentially I am asking, what evidence is there that tree rings are correlated to global temperatures at all? --Dilaudid (talk) 10:16, 3 February 2010 (UTC)


 * This is addressed in the CSM article we cite . See the e-mail from Rob Wilson, towards the end of the article. My personal, informed-outsider view (fwiw) is that the error-bars for the "treemometers" are probably understated: these are very noisy data, interpretation is not straightforward, and opportunities for confirmation bias are not insignificant. Best, Pete Tillman (talk) 20:06, 5 October 2010 (UTC)


 * What a horrible article. Do we really cite it? The evidence is that tree rings correlation to T over some of the observational period - say, 1860 to 1950 or thereabouts. Oh, and don't forget the problem is mostly for long-term variance. Year-to-yer variance is preserved, see which Tillman helps links below William M. Connolley (talk) 20:56, 5 October 2010 (UTC)

Esper & Frank 2009, Divergence pitfalls in tree-ring research
I don't see this one discussed here: full text online. Esper & Frank suggest that some reported divergences arise from data-handling errors, and might go away if the data were handled properly. The paper is labeled as an editorial and is pretty arm-wavy. I haven't yet read it carefully, and won't have time to do so for awhile -- so I'm posting it in case someone like WMC has digested it and can say if it's worth mentioning in our article, or not. Should get a line or so, I'd think:


 * [Draft] Some reported divergences may be artifacts of improper data-handling (Esper & Frank 2009).

It's not really suitable for "Further reading" by the general public, but does have a good, up-to-date bibliography on the topic. Thanks, Pete Tillman (talk) 19:41, 4 October 2010 (UTC)


 * I'm not sure how good or useful it is (I hadn't seen it before; thanks). It is, as you say, a bit hand-wavy and doesn't really say any of the divergence *is* caused by thes eproblems - just that some might be. Which is rather vague William M. Connolley (talk) 21:17, 5 October 2010 (UTC)

This article is woefully inadequate - needs an entire rewrite.
It seems a shame that such an interesting topic is treated in such a superficial manner. The article is riddled with inaccuracies and omissions - from the first two sentences alone: it is clumsy to describe the divergence problem as an "anomoly" and it is not a phenomenon affecting just ring width e.g. maximum latewood density is also affected. Many significant features of the issue are ignored e.g. there are problems in detecting if this is an in the issue in the first place in many chronologies where it apparently appears, and the fact that the issue can affect whole chronologies, subsets of chronologies and in some cases individual trees. The problem is observed on a decadal timescale, which is hugely significant for climate reconstructions, yet this is not mentioned anywhere in the article. There are also many possible explanations that are not touched on here e.g. the assumptions of a linear growth response to temperature when in fact the response in non-linear (e.g Craig Loehle's work) and the affect of regional curve standardisation (discussed by Keith Briffa, in many places), and many more.

Even the primary significance of the divergence problem for dendroclimatology is not mentioned - the "uniformitarianism" assumption, upon which all of dendroclimatology is based, is in fact called into question by the divergence problem. This is the assumption that the relationship between the environmental variable (more complex than simply "temperature" - not made clear in this article) we are considering and observed tree ring growth in recent times, also holds true for the past which we are attempting to reconstruct.

I would be willing to spend a bit of time reworking the article (I have spent some time studying this area in the past), but would prefer to start the article from scratch - this would mean replacing all the work currently on here. Is that acceptable? (somewhat of a wiki newbie...) — Preceding unsigned comment added by 82.22.196.56 (talk) 22:59, 25 May 2011 (UTC)


 * Why don't you first try a rewrite of the section you find most objectionable, and post it here for discussion?


 * Also, please sign up first for a Wikipedia account -- contributions from anonymi tend to get short-shrift here. Look forward to your proposal -- Pete Tillman (talk) 20:20, 12 June 2011 (UTC)

Taubes 1995 is not primary literature
Taubes 1995 certainly shouldn't be the first cite for this -- it was just a "Research News" article summarizing Jacoby & d'Arrigo (1995), which should be the primary cite. — Preceding unsigned comment added by Krabapple (talk • contribs) 18:01, 5 February 2014 (UTC)

The upside down parabola problem for tree response to temperatures
This is the widespread forestry observation that tree growth can decline if it's too warm or too cold -- with obvious implications for interpreting tree rings as "treemometers". See Loehle, C. 2009. A Mathematical Analysis of the Divergence Problem in Dendroclimatology. Climatic Change 94:233-245. He argues that tree rings can only be used for climatology going back the length of the local climate record,  100 yrs or so -- not the longer 1000+ years often attempted. Any comment from knowledgeable readers? --Pete Tillman (talk) 15:08, 18 November 2014 (UTC)