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Hayhoe Still Publicises The Discredited Marcott Hockey Stick

July 21, 2015

By Paul Homewood   




It seems that junk scientist Katharine Hayhoe is still showing the utterly discredited Marcott hockey stick on her Facebook page.

Which is perhaps a good time to remind her and everyone else of some of the problems found with it.

Ross McKitrick published a very good summary in the Financial Post soon after the Marcott paper was released in 2013:




On March 8, a paper appeared in the prestigious journal Science under the title A reconstruction of regional and global temperature for the past 11,300 years. Temperature reconstructions are nothing new, but papers claiming to be able to go back so far in time are rare, especially ones that promise global and regional coverage.

The new study, by Shaun Marcott, Jeremy Shakun, Peter Clark and Alan Mix, was based on an analysis of 73 long-term proxies, and offered a few interesting results: one familiar (and unremarkable), one odd but probably unimportant, and one new and stunning. The latter was an apparent discovery that 20th-century warming was a wild departure from anything seen in over 11,000 years. News of this finding flew around the world and the authors suddenly became the latest in a long line of celebrity climate scientists.

The trouble is, as they quietly admitted over the weekend, their new and stunning claim is groundless. The real story is only just emerging, and it isn’t pretty.


The article is under copyright, but the major criticisms are:



1) The Science paper was derived from Marcott’s PhD thesis, which used the same proxies and methods. But in that thesis there was no uptick in that chart, nor does the Abstract mention one.

2) A number of the proxies used in Marcott et al had been redated, thereby changing the mix of proxies which contributed to the closing values of the graph. If the original dates had been used, there would have been no uptick.

3) Worse still, the paper did not mention these changes.

4) When faced with these criticisms, Marcott was forced to issue this statement:

"The 20th-century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes, and therefore is not the basis of any of our conclusions”

5) Marcott then attempted to defend his findings by claiming that if you graft the 20th thermometer record onto the graph, there is still a large uptick at the end.

But as McKitrick points out,

“But you can’t just graft two completely different temperature series together and draw a conclusion from the fact that they look different.

The modern record is sampled continuously and as a result is able to register short-term trends and variability. The proxy model, by the authors’ own admission, is heavily smoothed and does not pick up fluctuations below a time scale of several centuries. So the relative smoothness in earlier portions of their graph is not proof that variability never occurred before. If it had, their method would likely not have spotted it.”

Put another way, if you took the average of the latest 300 years of CET, there would be no uptick at all!




As McKitrick concludes:

“What made their original conclusion about the exceptional nature of 20th-century warming plausible was precisely the fact that it appeared to be picked up both by modern thermometers and by their proxy data. But that was an illusion. It was introduced into their proxy reconstruction as an artifact of arbitrarily redating the end points of a few proxy records.

In recent years there have been a number of cases in which high-profile papers from climate scientists turned out, on close inspection, to rely on unseemly tricks, fudges and/or misleading analyses. After they get uncovered in the blogosphere, the academic community rushes to circle the wagons and denounce any criticism as "denialism." There’s denialism going on all right – on the part of scientists who don’t see that their continuing defence of these kinds of practices exacts a toll on the public credibility of their field.”



 HH Lamb

As Ross McKitrick points out, trying to estimate global temperatures thousands of years ago is a notoriously difficult task, given the lack of proxies. Nevertheless it is worth looking at what HH Lamb had to say about some of the dramatic climate changes that took place over the last few thousand years, which give the lie to the “smoothed” interpretation of events.

(It is worth pointing out here that, contrary to common opinion, much of Lamb’s work was not actually his own but was a compilation of the work of other experts over the years)


From “Climate, History and the Modern World”:


He starts by introducing ring-width and upper tree line analyses in the White Mountains of California, and the Swiss and Austrian Alps.






There is clear evidence of sudden and substantial changes in temperatures, as indicated by both ring-widths and the tree line, in both regions. Of course, this just tells about California and the Alps, but Lamb comments:


Other proxy indicators which give us a record, albeit less complete, of the history of the climate since 3000 BC include radiocarbon dated moraines and other traces of former glacial advances, also radiocarbon dated pollen analyses of the deposits in peat bogs and lake beds, and the study of the yearly layering of deposits such as that of Lake Saki in Crimea, and the ice caps of Greenland and Antarctica.

From all this material we can trace the course of the decline from the warmest post-glacial times in different regions of the world…. The changes seen in fig 53 indicate that by about 500-200 BC the long term temperature level in Europe was about 1C lower, and in the southwestern part of North America about 0.5C lower, than it had been in the warmest post-glacial period. These figures are modest compared with other assessments of some of the more abrupt changes in the last two millenia before Christ (and again in the late Middle Ages).

It is clear from fig 52 that the growth rings of the trees in California indicate a number of very sharp shorter term changes, in both directions, affecting the average temperature level over periods from a few years up to a few centuries, such have been deduced from the indications of past glacier advances and retreats in Europe and North America, and that these have exceeded the magnitude of the more persistent changes registered by the upper tree line.

The changes over a few centuries seen in fig 52, as around 1300-900 BC, before and after 1200 AD, and again since 1800, are more than twice as great as the differences in average ring thicknesses from millennium to millennium: they probably corresponded to changes of prevailing temperature by rather over 1C there [North America] and rather over 2C in Europe. In northern Canada, and probably elsewhere in high latitudes, the changes were greater still.


Lamb also finds similar patterns in Scandinavia, Central and South America, and New Zealand, where Neoglacial advance set in following sharp cooling around 1500 BC.

  1. Mark Hodgson permalink
    July 21, 2015 5:48 pm

    Yes, of course they love their hockey sticks, however discredited. There’s a conference coming up in Paris, you know.

    And the BBC really are doing their best to ramp up the ante. Apparently there’s nothing going wrong that can’t be blamed on increased CO2 and/or man-made climate change. Here’s this afternoon’s offering:

    “Emissions from fossil fuels may limit carbon dating” is the eye-catching headline. The link is here:

    • John Palmer permalink
      July 21, 2015 8:39 pm

      Is there no bit of silly unscientific sensationalism that the Beeb’s boys won’t use in the run-in to Paris???
      And it’s only July!
      It can only get more frantic.

    • Ben Vorlich permalink
      July 22, 2015 6:53 am

      That means they can send a couple of archeological reporters to Paris now! They just need to make a connection to a couple of sports and a team headed by Clare Balding can have a couple of week in Paris.

  2. Joe Public permalink
    July 21, 2015 5:57 pm

    It’s amazing that such a highly qualified scientist would produce and post chart that indicates earth’s temperature is hovering around -17 degC.

  3. igsy permalink
    July 21, 2015 6:45 pm

    For me, Marcott was the absolute final straw, as if one were needed after Mann’s original hockey stick, the Wahl/Ammann fiasco, and Mann’s “upside-down-proxies” hockey stick of 2008. The “Team” will defend any old rubbish, no matter how self-evidently absurd, to promote their alarmist worldview. There is simply nothing so scientifically and statistically god-awful that is too bad for them, provided it gives the “right” answer.

  4. July 21, 2015 7:26 pm

    The Marcott hockeystick is much worse than McKitrick’s critique (which is also valid). It comprises academic misconduct and should have been retracted by Science after I provided McNutt with the irrefutable evidence in writing nd her office acknowledged receipt. Essay a High Stick Foul in ebook Blowing Smoke. Hayhoe would have known or should have known this if Science had acted appropriately. It did not.

    • July 22, 2015 12:56 pm

      Marcott’s paper did not actually say what Science said it did. It clearly indicated the end of the hockey stick was intrumental temperatures that were not statistically significant, if I recall correctly (I read the actual paper.) Science seems to have left that part out of the publication of the paper. Marcott, had he been one to stick to the tenets of science should have cried out loudly that his paper was misinterpreted. However, after years of academic study and research, to do so probably would have cost him his phD. I am not saying he was right in not objecting, only that I can understand how someone could feel enough pressure to keep silent if they were not highly motivated to get the truth out there.

  5. John F. Hultquist permalink
    July 21, 2015 11:44 pm

    The junky right end of the Hayhoe/Marcott chart is now of no interest. Note, though, the rest of it. For about 6,000 years (if any of this is believable), Earth’s temperature has been declining. Uff da!

    • AndyG55 permalink
      July 22, 2015 12:42 am

      Gisp ice cores , Fram Straight biomarkers etc all confirm that the first 2/3 of the Holocene was warmer than now.

      The slight decline in temps over that first 6000 or so years became a sharper decline about 3000 years ago.. they even have a name for it, Neoglaciation.

      We are currently only just a small molehill out of the COLDEST period in the last 10,000 years…

      And its stopped getting warmer. !!!!!!

      Marcott’s graph is essentially the same shape as the Gisp data, but the range of the vertical axis is obviously going to be less if you add tropical data in with the higher latitude data.

    • AndyG55 permalink
      July 22, 2015 12:45 am

      Another video showing the same basic shape.

      Obviously some data will not pick up the sharper dips and peaks because of resolution constraints.

  6. Yippiy permalink
    July 22, 2015 9:42 am

    There was I, thinking that the width of tree rings depended on temperature, humidity and rainfall – it seems only temperature is considered. Am I missing something?

  7. cheshirered permalink
    July 22, 2015 1:11 pm

    For someone in her position to endorse Marcott’s rubbish reveals far more about her outlook and ethics than anything in the ‘study’ itself. Wilful misdirection.

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