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As The Economist points out: "The 'hiding' concerned the decision to leave out a set of tree-ring-growth data that had stopped reflecting local temperature cha

As The Economist points out: "The 'hiding' concerned the decision to leave out a set of tree-ring-growth data that had stopped reflecting local temperature changes. That alteration in growth pattern is strange, and unexplained, but eliminating it is not sinister." and: " 'I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) and from 1961 for Keith’s to hide the decline.' Trickery associated with Dr Mann was catnip to the sceptics. But Dr Jones has clarified that 'The word trick was used here colloquially as in a clever thing to do. It is ludicrous to suggest that it refers to anything untoward.' " http://www.economist.com/opinion/displaystory.cfm?story_id=14960149 http://www.economist.com/opinion/displaystory.cfm?story_id=1...

greendestiny 17y ago
If the tree-ring growth data doesn't match directly measured temperature at significant intervals of time (necessitating what amounts to arbitrarily changing data sources mid graph) why on earth would you trust it for periods where its the only data source. I think the evidence for AGW extends beyond this particular incident, but I think its highly unethical and very poor science.
- jsz0 17y ago
  Was it the only data source in other time periods? or was it collaborated by other data?
  - greendestiny 17y ago
    No idea, reasonable questions, but I don't see much redeeming about simply swapping data sets mid-graph.
    - tensor 17y ago
      That's a fair criticism, but it would be worth seeing the figure caption for it as well. If the caption had within it that the source was switched part way due to a known problem, that would be fine. Out of curiosity, anyone know a journal reference for that particular graph?
      - greendestiny 17y ago
        Comments on the OP suggest it was cover art. Not sure what to make of that without more context. Making it clear the data changed stops it being unethical, but I think the criticism of concatenating two data sources remains. Especially when the point of the graph is the sharp rise at the end - just as the data source changes. You really want to make sure the data sources correlate highly to make that kind of argument.
      - deleted 17y ago
        [deleted]
  - jacobolus 17y ago
    (off topic, but I think you mean corroborated :)
Perceval 17y ago
My concern about the tree-ring data is that, on face, it seems like tautological reasoning. Please correct me if I'm misrepresenting what's going on. The tree ring data, after a certain point in history, is no longer a reliable indicator of local temperature changes. There is no explanation for why trees no longer reflect local temperature changes. We know that they no longer reflect local temperatures, presumably, because we have other more reliable measurements available now (measurements that are not available further back in history). This leaves us with a conundrum: is there any period in which alternative measurements and tree-ring measurements correspond with one another? Is the divergence between our measurements and the tree-rings something we can trace? Is it sudden or gradual? If there is no period in which there is a correspondence between our measurements and the tree-rings, what does this say about our assumption that tree-rings have ever accurately captured local temperatures? It seems that the implication is that changes in the environment have rendered tree-rings unreliable. But if we're arguing that tree-rings are unreliable because of environmental change (i.e. the chemical changes to the composition of the atmosphere and water cycle that contribute to global warming), and we're seeking to explain environmental change, we're begging the question (assuming the explanandum in the premise of our argument). Until a causal mechanism for the divergence between tree-rings and other measured temperatures can be specified, how can they legitimately be discarded as evidence, without invoking tautological reasoning?
- algorias 17y ago
  If you don't have accurate data for a certain time period, it's preferable to have approximate data than none, as long as you take that lower accuracy into consideration.
  - j_baker 17y ago
    The thing is that upon that argument, we move from "blatant data-cooking" to "disagreement over scientific methods".
- btilly 17y ago
  And this is why people who don't know science should ask questions first. The tree ring data, after a certain point in history, is no longer a reliable indicator of local temperature changes. There is no explanation for why trees no longer reflect local temperature changes. We know that they no longer reflect local temperatures, presumably, because we have other more reliable measurements available now (measurements that are not available further back in history). There is NO SINGLE EXPLANATION for the discrepancy. This is NOT the same as there being no explanation. What happens instead is that if you look in specific localities you can find specific explanations. Increased acidity here. Drought conditions there. Insect infestations in another. And in yet another the correlation with temperatures remains. What happened is that after 1960 due to large scale changes in environment in many localities the correlation broke down, so the overall correlation broke down. But there is no single explanation because in different areas the specific reasons differ. This leaves us with a conundrum: is there any period in which alternative measurements and tree-ring measurements correspond with one another? Is the divergence between our measurements and the tree-rings something we can trace? Is it sudden or gradual? If there is no period in which there is a correspondence between our measurements and the tree-rings, what does this say about our assumption that tree-rings have ever accurately captured local temperatures? Actually there is about a century of comparative data before that which shows a good correlation. That is why we are willing to project temperatures back farther using that record. Now there is the possibility that there were previous periods which saw a similar breaking of the correlation. This question is a question of scientific debate. It seems that the implication is that changes in the environment have rendered tree-rings unreliable. But if we're arguing that tree-rings are unreliable because of environmental change (i.e. the chemical changes to the composition of the atmosphere and water cycle that contribute to global warming), and we're seeking to explain environmental change, we're begging the question (assuming the explanandum in the premise of our argument). There is no begging the question when we are also studying the mechanisms involved. Until a causal mechanism for the divergence between tree-rings and other measured temperatures can be specified, how can they legitimately be discarded as evidence, without invoking tautological reasoning? You are making two large assumptions here. The first is that there is a single causal mechanism. The second is the assumption that we don't actually understand the mechanisms involved. Both assumptions are wrong. Look. Scientists aren't exactly stupid people. When they spend a lifetime studying something, you should assume that they've asked the obvious questions and try to find out the answers they have found rather than assuming that they are stupid and you're the first to notice the glaring issues. Unfortunately climate scientists are also humans who are under constant assault from people who can't and won't be bothered to actually learn the record. People who feel they are under constant assault engage in defensive behavior. And people who are being defensive tend to circle the wagons and have difficulty in remaining open with outside groups. When you encounter such defensive behavior I strongly recommend trying to understand what the defensive person's position is rather than immediately piling on and validating their defensiveness. If they are wrong, this approach leaves you in a better position to figure that out. But if they have a point, you'll be more likely to figure that out as well.

greendestiny 17y ago

If the tree-ring growth data doesn't match directly measured temperature at significant intervals of time (necessitating what amounts to arbitrarily changing data sources mid graph) why on earth would you trust it for periods where its the only data source. I think the evidence for AGW extends beyond this particular incident, but I think its highly unethical and very poor science.

jsz0 17y ago
Was it the only data source in other time periods? or was it collaborated by other data?
- greendestiny 17y ago
  No idea, reasonable questions, but I don't see much redeeming about simply swapping data sets mid-graph.
  - tensor 17y ago
    That's a fair criticism, but it would be worth seeing the figure caption for it as well. If the caption had within it that the source was switched part way due to a known problem, that would be fine. Out of curiosity, anyone know a journal reference for that particular graph?
    - greendestiny 17y ago
      Comments on the OP suggest it was cover art. Not sure what to make of that without more context. Making it clear the data changed stops it being unethical, but I think the criticism of concatenating two data sources remains. Especially when the point of the graph is the sharp rise at the end - just as the data source changes. You really want to make sure the data sources correlate highly to make that kind of argument.
    - deleted 17y ago
      [deleted]
- jacobolus 17y ago
  (off topic, but I think you mean corroborated :)

Perceval 17y ago

My concern about the tree-ring data is that, on face, it seems like tautological reasoning. Please correct me if I'm misrepresenting what's going on. The tree ring data, after a certain point in history, is no longer a reliable indicator of local temperature changes. There is no explanation for why trees no longer reflect local temperature changes. We know that they no longer reflect local temperatures, presumably, because we have other more reliable measurements available now (measurements that are not available further back in history). This leaves us with a conundrum: is there any period in which alternative measurements and tree-ring measurements correspond with one another? Is the divergence between our measurements and the tree-rings something we can trace? Is it sudden or gradual? If there is no period in which there is a correspondence between our measurements and the tree-rings, what does this say about our assumption that tree-rings have ever accurately captured local temperatures? It seems that the implication is that changes in the environment have rendered tree-rings unreliable. But if we're arguing that tree-rings are unreliable because of environmental change (i.e. the chemical changes to the composition of the atmosphere and water cycle that contribute to global warming), and we're seeking to explain environmental change, we're begging the question (assuming the explanandum in the premise of our argument). Until a causal mechanism for the divergence between tree-rings and other measured temperatures can be specified, how can they legitimately be discarded as evidence, without invoking tautological reasoning?

algorias 17y ago
If you don't have accurate data for a certain time period, it's preferable to have approximate data than none, as long as you take that lower accuracy into consideration.
- j_baker 17y ago
  The thing is that upon that argument, we move from "blatant data-cooking" to "disagreement over scientific methods".
btilly 17y ago
And this is why people who don't know science should ask questions first. The tree ring data, after a certain point in history, is no longer a reliable indicator of local temperature changes. There is no explanation for why trees no longer reflect local temperature changes. We know that they no longer reflect local temperatures, presumably, because we have other more reliable measurements available now (measurements that are not available further back in history). There is NO SINGLE EXPLANATION for the discrepancy. This is NOT the same as there being no explanation. What happens instead is that if you look in specific localities you can find specific explanations. Increased acidity here. Drought conditions there. Insect infestations in another. And in yet another the correlation with temperatures remains. What happened is that after 1960 due to large scale changes in environment in many localities the correlation broke down, so the overall correlation broke down. But there is no single explanation because in different areas the specific reasons differ. This leaves us with a conundrum: is there any period in which alternative measurements and tree-ring measurements correspond with one another? Is the divergence between our measurements and the tree-rings something we can trace? Is it sudden or gradual? If there is no period in which there is a correspondence between our measurements and the tree-rings, what does this say about our assumption that tree-rings have ever accurately captured local temperatures? Actually there is about a century of comparative data before that which shows a good correlation. That is why we are willing to project temperatures back farther using that record. Now there is the possibility that there were previous periods which saw a similar breaking of the correlation. This question is a question of scientific debate. It seems that the implication is that changes in the environment have rendered tree-rings unreliable. But if we're arguing that tree-rings are unreliable because of environmental change (i.e. the chemical changes to the composition of the atmosphere and water cycle that contribute to global warming), and we're seeking to explain environmental change, we're begging the question (assuming the explanandum in the premise of our argument). There is no begging the question when we are also studying the mechanisms involved. Until a causal mechanism for the divergence between tree-rings and other measured temperatures can be specified, how can they legitimately be discarded as evidence, without invoking tautological reasoning? You are making two large assumptions here. The first is that there is a single causal mechanism. The second is the assumption that we don't actually understand the mechanisms involved. Both assumptions are wrong. Look. Scientists aren't exactly stupid people. When they spend a lifetime studying something, you should assume that they've asked the obvious questions and try to find out the answers they have found rather than assuming that they are stupid and you're the first to notice the glaring issues. Unfortunately climate scientists are also humans who are under constant assault from people who can't and won't be bothered to actually learn the record. People who feel they are under constant assault engage in defensive behavior. And people who are being defensive tend to circle the wagons and have difficulty in remaining open with outside groups. When you encounter such defensive behavior I strongly recommend trying to understand what the defensive person's position is rather than immediately piling on and validating their defensiveness. If they are wrong, this approach leaves you in a better position to figure that out. But if they have a point, you'll be more likely to figure that out as well.