4 ms·

It's even better if you read the Briffa letter to Nature that he cited: http://www.nature.com/nature/journal/v391/n6668/abs/391678a0.html http://www.nature.com/

by thras 17y ago

It's even better if you read the Briffa letter to Nature that he cited: http://www.nature.com/nature/journal/v391/n6668/abs/391678a0.html http://www.nature.com/nature/journal/v391/n6668/abs/391678a0... Something completely unknown is making tree rings too small after 1960. And if you correlate your tree ring data to post-1960 temperatures it makes historical temperature look way too high. Bizarro-Briffa sent a similar letter to Bizarro-Nature warning of an unknown divergence problem and saying not to correlate tree rings to pre-1960 temperatures because it makes historical temperature look way too low.

spoondan 17y ago
I don't know what you're trying to argue. Tree rings underestimate current, not historical, temperatures. This means that, yes, if you calibrate to current temperature, the past will look comparatively hotter. This is a causal relationship.
- waterlesscloud 17y ago
  At what other periods to tree rings not correctly correlate to temperature? How do we know the last 50 years is the only time this has happened? Since we do not know why the temperature has not correctly correlated over the last 50s years, we can't really know when else that has been the case, can we? So why do we rely on tree rings for any period? They are proven to be unreliable over a signifcant period, and we don't know if or how often that's also true of the past.
  - spoondan 17y ago
    You can cross-check historical reconstructions to assess their accuracy for given periods. I don't know how often this has been done and if other significant, unexplained, and unaccounted for divergences have been found. I haven't heard of any, but I'm not an expert. For complete answers to your questions, I'm afraid you may have to review the literature.
    - foldr 17y ago
      If you're not an expert, please don't claim that it's feasible to cross-check this data against historical reconstructions -- you clearly do not know whether it is or not.
      - smcq 17y ago
        I'm not an expert in climate change either, but I'm a journeyman in statistics and I support his claim that it can be correlated.
        foldr 17y ago
        How can you support that claim without having any relevant knowledge? I don't see that a general knowledge of statistics is particularly relevant here -- we're all well aware that things can, in general, be correlated.
        gnaritas 17y ago
        Scientists don't rely solely on tree ring data for historical temperatures, it's one of many methods used. Thus the tree ring data can be correlated against other measurements to know it's accurate for past time periods. This should be obvious.
        foldr 17y ago
        > This should be obvious. Thus, either (a) it has already been done, or (b) it is more difficult than you would expect for non-obvious reasons. So what is your point? Have you even bothered to find out if anyone has done it or not?
        smcq 17y ago
        Fallacy of bringing absolutely nothing to the debate and asserting to the point of ad homonim that scientists would have skipped basic statistics on their data. Please see the post immediately above yours and go demonstrate that the method is flaw before continuing this debate. The standard of evidence to show fault is yours. Assuming that papers published in freaking NATURE have sound statistics is a reasonable thing for a layman to do.
  - Tichy 17y ago
    I think you are confusing politics and science here. Apparently some scientists study the correlation between tree ring growth and temperature. This is a perfectly valid research area. It is OK to publish articles about, to announce to the world that at some time the correlation went away. Climate research is research. It is not some know-it alls claiming one thing or another. It is making up theories and testing and aligning them with available data. It is trying to get new sources for data. And so on. It is an ongoing process. Science never KNOWS anything. It only assigns weights and likelihoods. We don't know if all history of earth is just an illusion, because we could just be a computer simulation that started 10 seconds ago. So we will never KNOW if tree ring data at all times before 1960 correlated with temperature. All we can do is to collect evidence, make up theories and compare them with reality. Disclaimer: I am not a climate researcher myself.

by thras 17y ago

spoondan 17y ago

I don't know what you're trying to argue. Tree rings underestimate current, not historical, temperatures. This means that, yes, if you calibrate to current temperature, the past will look comparatively hotter. This is a causal relationship.

waterlesscloud 17y ago
At what other periods to tree rings not correctly correlate to temperature? How do we know the last 50 years is the only time this has happened? Since we do not know why the temperature has not correctly correlated over the last 50s years, we can't really know when else that has been the case, can we? So why do we rely on tree rings for any period? They are proven to be unreliable over a signifcant period, and we don't know if or how often that's also true of the past.
- spoondan 17y ago
  You can cross-check historical reconstructions to assess their accuracy for given periods. I don't know how often this has been done and if other significant, unexplained, and unaccounted for divergences have been found. I haven't heard of any, but I'm not an expert. For complete answers to your questions, I'm afraid you may have to review the literature.
  - foldr 17y ago
    If you're not an expert, please don't claim that it's feasible to cross-check this data against historical reconstructions -- you clearly do not know whether it is or not.
    - smcq 17y ago
      I'm not an expert in climate change either, but I'm a journeyman in statistics and I support his claim that it can be correlated.
      - foldr 17y ago
        How can you support that claim without having any relevant knowledge? I don't see that a general knowledge of statistics is particularly relevant here -- we're all well aware that things can, in general, be correlated.
        gnaritas 17y ago
        Scientists don't rely solely on tree ring data for historical temperatures, it's one of many methods used. Thus the tree ring data can be correlated against other measurements to know it's accurate for past time periods. This should be obvious.
        foldr 17y ago
        > This should be obvious. Thus, either (a) it has already been done, or (b) it is more difficult than you would expect for non-obvious reasons. So what is your point? Have you even bothered to find out if anyone has done it or not?
        smcq 17y ago
        Fallacy of bringing absolutely nothing to the debate and asserting to the point of ad homonim that scientists would have skipped basic statistics on their data. Please see the post immediately above yours and go demonstrate that the method is flaw before continuing this debate. The standard of evidence to show fault is yours. Assuming that papers published in freaking NATURE have sound statistics is a reasonable thing for a layman to do.
- Tichy 17y ago
  I think you are confusing politics and science here. Apparently some scientists study the correlation between tree ring growth and temperature. This is a perfectly valid research area. It is OK to publish articles about, to announce to the world that at some time the correlation went away. Climate research is research. It is not some know-it alls claiming one thing or another. It is making up theories and testing and aligning them with available data. It is trying to get new sources for data. And so on. It is an ongoing process. Science never KNOWS anything. It only assigns weights and likelihoods. We don't know if all history of earth is just an illusion, because we could just be a computer simulation that started 10 seconds ago. So we will never KNOW if tree ring data at all times before 1960 correlated with temperature. All we can do is to collect evidence, make up theories and compare them with reality. Disclaimer: I am not a climate researcher myself.