Assuming the Conclusion

Bishop Hill Blog writes, concerning the truncation of recently divergent data by Keith Briffa and others:

The point at issue is Mike’s Nature Trick and the question of whether it amounts to scientific fraud. Der Spiegel describe the trick as follows:

But what appeared at first glance to be fraud [“hide the decline”] was actually merely a face-saving fudge: Tree-ring data indicates no global warming since the mid-20th century, and therefore contradicts the temperature measurements. The clearly erroneous tree data was thus corrected by the so-called “trick” with the temperature graphs.

Many of Roger’s readers take issue with the description of the divergent data as “erroneous” and I tend to agree with them here. The data has been processed in the same way in the twentieth century as in earlier periods, so it is not erroneous, but anomalous. The reason for the divergence is unknown and the divergence therefore needs to be disclosed and discussed since it potentially undermines all tree-ring based temperature reconstructions.

Here is an example of data you might reasonably throw out as erroneous:   Drop a ball a thousand times from a building and measure its acceleration.  We know its going to be something like 9.8 m/sec/sec.  If four or five times we measure it as 5 m/sec/sec, we will likely treat those measurements as erroneous, since we have hundreds of years of historical measurements to confirm the acceleration near the Earth’s surface due to gravity.

Here is another example:   You have ten identical compasses.  Nine of them say north is in the direction of the tree in your backyard.  The tenth say it is behind you.  We might reasonably throw out the tenth observation as erroneous.

Here is a different kind of example.  From 1936 to 2000, the winner of the last Washington Redskins home game accurately predicted the winner of that year’s presidential election.  Then, in 2004 the relationship between Redskin’s performance and the presidential election did not hold.   So, should we throw out the data point as anomalous, or should we use this data point to force ourselves to reconsider whether the relationship was ever really a valid causality?

The Mann/Briffa/etc. tree ring analyses assume the following:  That tree ring growth varies linearly with average temperatures; that the temperature-growth relationship is far stronger and more dominant than relations between soil conditions, rain, sunlight, or any other environmental factor and tree growth; and that this relationship remains fairly constant over the life of a tree.

The question is, do we believe these assumptions in the same way that we believe that the acceleration of gravity is 9.8 m/sec/sec?  By throwing out the data after a certain date, which by the way was gathered from the exact same trees by the exact same methodology as the earlier data, Briffa and others are in effect saying that their assumptions about the relationship between tree ring growth and temperature are unassailable, despite the fact that these analyses have only really been done for a few years.

Reasonable people instead will tend to conclude that it is instead very possible that the divergence problem the author’s sought to hide is in fact evidence that tree rings make poor thermometers – than one or all of the assumptions about tree rings and their relationship with temperature are flawed.

  • ted rado

    This article reinforces the necessity of calm, objective research and analysis. The whole climate thing has long ago degenerated into childish bomb throwing. Condidering that many are proposing the destruction of our industrial society, we had better be right in our analysis. It would be a blessing if everyone went back to the beginning, reviewed all available data and hypotheses, and calmly studied and debated the issue. In my sixty years as an engineer, I have never seen anything as childish and unprofessional. I would have been fired immediately if I had done my work via zealotry, hysteria, and shouting.

  • Karl Kessel

    It’s worse than that. People inside the group thought that the divergence problem and the statistical uncertainties undid dendroclimatology and yet it was still defended and anyone who questioned it was persecuted.

    The relevant email is from Ed Cook and the summary puts it nicely:

    ————-

    Without trying to prejudice this work, but also because of what I
    almost think I know to be the case, the results of this study will
    show that we can probably say a fair bit about 100 year variability was like with any certainty (i.e. we know
    with certainty that we know fuck-all).

    ————-

    http://www.eastangliaemails.com/emails.php?eid=356&filename=555-5555.txt

    Now, the question is, if the alarmists were prepared to defend something that they had very, very good reason to believe was very seriously suspect why should the same group be trusted to produce an unbiased summary of other climatology? Given that and the efforts to suppress papers pointing out problems with the computer models and the awful work in WG2 & WG3 many, many people would say that quite simply that climatology and the IPCC is deeply, deeply corrupt.

  • AnonyMoose

    In 1998, 12 years ago, wasn’t the divergence problem described as having been widely known by dendro scientists? How much progress has been made by research into the divergence problem? What research has taken place?

  • Max

    The funny thing is that they could have very well argued that these termperature data was faulty (though they would have to demonstrate WHY that is!), but in this case they would have to cut all their tree-rings after this point and not just some inconvient ones. If they want to keep them, then they have to explain the divergence, which they did not in a satisfying manner.

    There is no scientific problem in “we don’t know what happens after this point, but we are sure before about the time before it” or something like “the divergence has to be further examined, therefore data beyond XXXX is highly uncertain”. However, that they not did this is sloppy work that borders on fraud, because they were pointed towards it I think a million times.

  • Max said: “There is no scientific problem in “we don’t know what happens after this point, but we are sure before about the time before it” or something like “the divergence has to be further examined, therefore data beyond XXXX is highly uncertain”.”

    I agree, except didn’t the data also diverge regarding the MWP and LIA? Should not those divergence periods also be examined, along with any others?

    Max continues: “However, that they not did this is sloppy work that borders on fraud, because they were pointed towards it I think a million times.”

    Agree again.

  • Jay

    If tree ring data can not be accurately correlated with instrument recorded temperature data in the 20th century, how could anyone claim it is robust to use tree ring data as a proxy for temperatures from year 1000-1900? Physics and biology did not suddenly change in 1900. The truth is that Briffa and Mann emphasized tree ring data as a temperature proxy when it provided the results they wanted, then concealed the proxy when it conflicted with actual instrument measured temperature data. The point is, if tree rings don’t work as a proxy for temperatures int he 20th century, then they are not a reliable proxy for the preceding 1400 years either.

  • Wally

    Jay,

    Its impossible to put it any more succinctly than you just did. Briffa and Mann quite obviously cherry-picked their data in favor of the desired conclusion. IMO, any scientist that does that should be removed from their position.

  • I could not agree more.

    Expect some flak, though – this has been distributed as one of today’s ‘Climate Change sceptic blog alerts’ distributed by the ‘Campaign against Climate Change aggregator’. This is an alert to let warmists descend en masse to put their point of view against any blog post or article. It’s been the Guardian and Daily Mail/Express so far, but they are obviously looking further now.

    I should be so honoured! Good luck with the crowd coming to provide helpful abuse (this is my experience, anyhow).

  • Ditto

    JEROME – These climate change sceptic blog alerts are easy enough to sign up to. I have – and I am not an Alarmist – very much a sceptic.

    So I suggest we of a healthy sceptical viewpoint sign up – I have! – and that is how I now post a dose of realism to counter the Alarmist spin.

    Nothing like using the spinmasters own tools against them!

  • “The question is, do we believe these assumptions in the same way that we believe that the acceleration of gravity is 9.8 m/sec/sec?”

    It depends who you mean by “we.” Your typical warmist scientist believes that the Earth is warming unprecedentedly and dangerously the same way that you or I believe that the Earth is round.

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