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Katharine Disappears The MWP

November 10, 2014

By Paul Homewood





Bishop Hill reports on Katharine Hayhoe’s latest book, which includes the above graph. The provenance is not clear, but apparently she was showing the same graph as long ago as 2010, so it predates last year’s Marcott study.


I won’t dwell on her claim that it is much warmer now than in the MWP, contrary to much evidence from around the world. But I do want to comment on her assumption that temperature changes in the last few thousand years have been smooth and gradual.

Let’s see what HH Lamb had to say about this period in his book, “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.


So Lamb finds ample evidence, not only that the climate has been warmer than now in the recent past, but, significantly, that temperature changes over a periods of decades and centuries have been sharp and significant.

These sudden and short term changes do not appear on Hayhoe’s smoothed graph, which, of course, has the actual temperature record grafted on the end. There is no evidence that temperature trends in the last century or so have not been repeated, in both directions, several times over the course of the last few millennia.




HH Lamb – “Climate, History and the Modern World”  

pp 139-146

  1. November 10, 2014 6:48 pm

    these Katherines are the people who donot even understand the very basics of chemistry. Any (good) chemist knows that there are giga tons and giga tons of bi-carbonates dissolved in the oceans and that (any type of) warming would cause it to be released:

    HCO3- + heat => CO2 (g) + OH-.

    This is the actual reason we are alive today. Cause and effect, get it? There is a causal relationship. More warming naturally causes more CO2. It is not the other way around, as Al Gore alleges in his movie (where he also goes up the his step ladder). . Without warmth and carbon dioxide there would be nothing, really. To make that what we dearly want, i.e. more crops, more trees, lawns and animals and people, nature uses water and carbon dioxide and warmth, mostly. Our God is great and worked out the exact time in space and time when we would need this CO2 most……The fact that humanity adds a bit of carbon dioxide to the atmosphere is purely co-incidental, and appears to be beneficial, if you want to have a green world.


    have not heard from Al Gore for a while.
    He probably made enough money with his CO2 nonsense movie?

    • Keith Willshaw permalink
      November 10, 2014 10:08 pm

      More likely the 20% of the $500 million dollars in oil money that he got from the sale of his ‘environmental’ channel Current TV to Al Jazeera which is of course funded by the Emir of Qatar.

      This is the same Al Gore who’s supporters claim that his critics are funded by big oil.

  2. Mikky permalink
    November 10, 2014 10:00 pm

    So nice to see the maintenance of the Fahrenheit scale, even if just for propaganda purposes in this instance.

  3. Streetcred permalink
    November 10, 2014 10:19 pm

    Katherine’s ‘Moses moment’ has been going on for too long … mental illness ?

  4. Mikky permalink
    November 10, 2014 10:23 pm

    Paul, have you ever looked at the seasonal profile of rises in annual mean temperatures? Looking at some Australian data (Deniliquin) I’ve just noticed that all the recent rise in annual maximum temperatures is coming from autumn and winter months. Headlines like “Hottest year EVAH, we’re all going to fry” might have to be countered with “Hottest year EVAH, thanks entirely to warmer winters”.

    • November 10, 2014 10:47 pm

      Last time I looked for the UK, it seemed to be Spring, which seems like a pretty good thing.

  5. November 10, 2014 11:52 pm

    Thanks, Paul.
    The Bishop will not like it, but the graph is hockey stick. It’s not dead!

    • November 11, 2014 9:17 am

      But as Mikky at 10:00 notices – the scale is Fahrenheit, to exaggerate the visual impression.

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