the Air Vent

Because the world needs another opinion

The State of Paleoclimate Understanding

Posted by Jeff Id on April 9, 2013

In the huge amount of justified complaints made here about what I think of paleo-reconstructions, one detail is probably lost in the chaff.

I really wish I knew what historic temperatures were.  You can’t read that much paleoclimate information and not want to know.   Steve McIntyre clearly inspired my reading, and unfortunately the inspiration came through a wholly skeptical lens.  In time it has turned out that the skeptical perspective of the statistics and  data in paleoclimate were 100% justified.

With data so noisy, yet so full of potential revelations, scientists are also justified in their interest.  As time has passed, I’ve grown to understand that there isn’t really any known solid way to divine the history of climate.  We have enough clues to see past warmth and plenty of clues to show deep past ice ages, yet the trivial level of understanding of past temperature is quite distant from the equivocation-ridden certainty of present day scientific publications.

Ed Cook was no small player in the paleoclimate field.  His own words have a ton of meaning for those who have enough understanding of the pervasive nuance in the field:

  the results of this study will show that we can probably say a fair bit about <100 year extra-tropical NH temperature variability (at least as far as we believe the proxy estimates), but honestly know fuck-all about what the >100 year variability was like with any certainty (i.e. we know with certainty that we know fuck-all).

This statement is an absolute scientific truth to my understanding.   There are multiple sentiments in it which have very solid meaning in interpreting these hockey stick plots.   First, and most interesting for those of us who actually want to know the truth, dendros seem to have discovered a way to see short term climate variation a very long time ago.   Variations on a scale of <100 years are also important because they give us some partial understanding of climate.   Unfortunately, Ed and I disagree as to the certainty of the meaning of even these short term variations.

That known correlation in itself is extremely cool. Skeptics of dendro question the linearity of these fluctuations with respect to temperature, but the short-term fluctuations themselves are highly correlated in local regions.  We can say that whatever was happening in climate to those regions, is measurable, and good plant growth years in one location were good plant growth years.  Not exactly known temperature “climate”, but growth climate is still a very cool thing.

Ed Cook knows the difference between short and long term variations, and after performing tree ring standardizations as I have, you get an understanding of why the long term signals (trends) in dendro hockeysticks are not likely represented by the data.  The math and physics simply don’t allow it.  Long term temperature trends derrived from tree rings, are necessarily quite meaningless.

Paleoclimate is noisy, and little is truly known in my opinion.   Better data is required, and despite the every-month premature conclusions from the experts, we shouldn’t lose site of the fact that once we discover the right proxy (or proxy combination), the math will not be the issue and finally we will know a true piece of our distant climate history.

Whatever we find out, that day when we finally know, will be an interesting day for me.

20 Responses to “The State of Paleoclimate Understanding”

  1. j ferguson said

    paleo-reconstructions seem like trying to do signal detection without knowing what the signal looks like. I’ve assumed that tree-rings won’t cut finer than annual, Maybe something with higher frequency would be more revealing. Is there anything like that?

  2. I believe proxies are dead and it is time to go back to historical documents describing the weather and crops grown etc.

  3. Interesting echoes of Marcott et al here:

    “Our data set exhibits several important strengths, as well as limitations, as compared to global and hemispheric reconstructions of the past 1500 years (2, 3, 7, 8). For example, whereas reconstructions of the past millennium rapidly lose data coverage with age, our coverage increases with age (Fig. 1, G and H). Published reconstructions of the past millennium are largely based on tree rings and may underestimate low frequency (multicentury-to-millennial) variability because of uncertainty in detrending (9) [although progress is beingmade on this front (10)],whereas our lower-resolution records are well suited for reconstructing longer-term changes.”

    • Give it up, Mr. Stokes. Marcott et. al. has far too many inconsistencies to be considered an authoritative paper, pal reviewed or not. It isn’t science, it’s politics, rushed out to give credence to the prejudices of the discredited IPCC, and the blinkered support by CAGW supporters does both the paper, it’s authors and the supporters themselves a disservice.

  4. Today’s proxies seem nearly dead but they have potential. What if you had plotted known response of three kinds of proxy to moisture, temperature etc.. and you solved multiple simulteneous equations to extract the signals individually. Different types of trees might be used to extract a clean moisture signal, I still doubt you could get temp but who knows.

    • Mark T said

      and you solved multiple simulteneous equations to extract the signals individually.

      Technically, that’s what PCA does. It’s just a solution to a linear system of equations.

      Unfortunately, it a) requires some semblance of stationarity in the noise, b) requires some semblance of linearity, c) requires that the “signals” are at least reasonably orthogonal (temp and CO2 are correlated by hypothesis, self-licking ice-cream cone there if I ever saw one), and d) does not attach nifty post-it notes to each of the resulting components for easy matching later.

      Mark

  5. diogenes said

    Jeff

    Just bringing Jim Bouldin’s blog to your attention. He has been running a series of posts that seem to demonstrate quite conclusively that it is impossible to extract a meaningful temperature series from tree-rings.

    http://ecologicallyoriented.wordpress.com/2013/03/21/severe-analytical-problems-in-dendroclimatology-part-twelve/

  6. ALL CHANGE, Climate is now 4 years of weather!!!!

    The Sun UK Newspaper

    “BRITAIN’S winters are getting colder because of melting Arctic ice, the Government’s forecaster said

    yesterday.
    “Met Office chief scientist Julia Slingo said climate change was “loading the dice” towards freezing,

    drier weather — and called publicly for the first time for an urgent investigation.”
    Prof Slingo said: “If you look at the way our weather patterns have behaved over the past four or five

    years, we’re beginning to think that there is something happening. “

    BRITAIN’S winters are getting colder because of melting Arctic ice, the Government’s forecaster said

    yesterday.

    Met Office chief scientist Julia Slingo said climate change was “loading the dice” towards freezing,

    drier weather — and called publicly for the first time for an urgent investigation.

    Prof Slingo said: “If you look at the way our weather patterns have behaved over the past four or five

    years, we’re beginning to think that there is something happening……….

    “Our climate is being disrupted by the warming of the Arctic that we have observed very dramatically

    since 2007.

    “We should pull together the best scientists to see how we can detect the influence of the Arctic on the

    jet stream, and on weather around the world.”

  7. Robert Austin said

    Proxy temperature reconstructions, the modern equivalent of the ancient practice of the reading of the entrails.

  8. Matthew W said

    ” yet so full of potential revelations”.

    If the professional climate sciencetologists were to tell the truth, would we know better what historic paleo temps would be?

  9. Brian H said

    And we shouldn’t lose sight of the fact that you can’t pick sites after the fact (during the analysis). They have to be cited up front. See?

  10. The stick is a meaningful measure of past climate, that is up until the industrial age. I worked out a data and plotted it and it also shows that climate temperature wise is rather stable for the past 5 kyrs and about 2 degrees C over the past 10,000 years. My illustration Ill 7.7 in Volume II is the Crowning Jewel in my theory of paleoclimate change. That means that a climate servo turned on at about 10 ka. But, servos are sensitivity to noise and Modern Man is a noisy bunch. This means that so long as there isn’t a major disturbance in the elements of the servo that temperatures will remain constant to within a narrow range. But, human activity is the noise here and we can expect grave consequences for the future.

    It is odd that humans would prefer glacial conditions rather than a warm paradise. However, the past climate never reach a paradise state and why would I think is will in the future. At high temperaturesm there will be desertification and huge dust storms with high velocity winds.

    But, what was the cause of the massive swings in climate from 1.2 ma to the PHT. Poly-Celestial Structures.

    Two additional things.
    The 8,200 ka cooling event is well described in my Volume II illustration Ill 7.7 and is very different from what has been propagated as the cause.

    No matter the quantity of CO2, there must be an energy source able to provide that needed to warm the Earth. One greater than solar to bring on Termination I and all the others.

    Thanks,
    Everette L. Wampler

  11. jim2 said

    And, some sorts of proxies average the signal over time. When these are used in comparison with modern temp measurements or even more modern proxies with higher resolutions; it can exaggerate the magnitude of modern temperatures.

  12. HaroldW said

    O/T: Two Antarctic publications in which you may be interested:
    Steig et al. have a letter discussing precipitation: more recently but no strong conclusions.
    Abram et al. discuss a “tipping point” in surface melt on the Antarctic peninsula.

  13. Kenneth Fritsch said

    Jeff, I also hope some day that proxies will be found and developed that will be able to make valid assessments of past temperatures. That development will require a sea change in how the selection of proxies is currently handled. It will require proxiy selection based on well understood and reasonable physics/chemistry/biology and will require that selections be made prior to data collection and calibration. I think there are more than a few of us who understand how easily a upward trending proxy to “match” the modern warming is to find after the fact and also realize that that trending can occur by chance.

    Why is not the proper selection process understood by otherwise intelligent and scientifically oriented people is a question I have pondered for some time now. I have seen this misunderstanding revealed with my participation in an investment blog awhile back where intelligent people could not comprehend the difference between in-sample and out-of-sample testing and the dangers of using in-sample tests to develop an investment strategy. Like some climate scientists I think part of the problem was that these investors wanted to believe in a system. The other part, I think, comes from the environment that hard scientists and enginners often work whereby they can control the conditions of their experiments – unlike investing or climate change. Under those circumstances one can theorize and do preliminary testing with immunity because one can always test those theories with a controlled experiment.

    • Anonymous said

      There are clues to the thought process in the climategate emails. The guys seem to intuitively know that there is a temperature signal, they also know that they cannot assume otherwise or the field itself would vanish.

      They really believe in what they are doing but they have lost all objectivity regarding justifiable (obvious) critiques which would invalidate the entire field. They simply cannot ask the tough questions even to each other.

  14. Of course the current pause in temperatures may be due to the way the temperature record has been obtained. There is a graph of the number of temperature stations vs. global temperatures and the correlation between the reduction in stations and the rapid rise in temperature is remarkable.

    http://www.uoguelph.ca/~rmckitri/research/nvst.html

    If the number of stations over the last 20 years is now relatively stable and the method of computing global temperatures is now also stable then things like UHI effects would be also relatively stable so we may now be getting an accurate reflection of global temperatures and the fiddling with the older temperature records would not be important as those records are before the reduction in the number of stations. This would mean that supposition that these last years have been much warmer than previous years is a fallacy, perhaps they are just a bit warmer and the temperature records are at fault.

  15. We do know from biological data from experiments and in-situ studies that the indicated increase in temperatures is in general correct. There are numerous species whose reproduction or growth triggers, or physical extant are well correlated with temperature. This does not include tree-rings because the rings used are from long living species and in conditions where water, nutrients, and negatives such disease or infestation can have a marked effect, and cannot be known.

    The answer to objectively account for the problems with such a biological organism are known,; but the answer has not been found for temperature proxies in main part since they are cliamte proxies. Quite frankly, some of the known prerequisites such as large sample numbers, in and out of sample techniques, cross validation techniques, a priori justification and model validation for biological specimens, and other tools and requirements simply are ignored.

    Thus at Climategate, Dr. Briffa’s comment that paleoclimatologists were “working” on the problems. This was before the MSM switched the argument to the strawman that the argument was about whether the current temperature increase over the historical was real.

    In the archives here at tAV, there are posts concerning all these issues, and what was actually the most damning information about Climategate.

  16. Genghis said

    Like my Mama used to say “If pigs could fly, they would have wings.”

    I think we are going a step too far trying to ascertain precise global temperatures from tree rings, sediment layers and layers of ice. Sure there may be a temperature signal in there, but at best it is a seasonal, regional, snapshot.

    The reality is that global temps have to stay relatively constant, within a few degrees of 5˚ C (the temperature of the oceans). Which oddly enough is the S-B number for a blackbody earth. Odd how that works isn’t it? : )

  17. Not exactly, but they’re closely related, and some people use the terms interchangeably. Global warming causes climates to change. “Global warming” refers to rising global temperatures, while “climate change” includes other more specific kinds of changes, too. Warmer global temperatures in the atmosphere and oceans leads to climate changes affecting rainfall patterns, storms and droughts, growing seasons, humidity, and sea level.

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