Gaps in tree rings sequences

24 Aug 2014

Tim Cullen appears to continue to be impressed by Gunnar Heinsohn's articles at (and another one has been posted over the last couple of days). Hence, in this look at the dendrochronology process he is looking for the possibility of an error in the region of 700 years of time being taken out of the first millennium AD. Therefore, he has an agenda. I'm not knocking it - just saying. What he has discovered is that there are two gaps in the sequences - one in the first millennium BC (at the point of the C14 curve) and the other in the first millennium AD. These gaps are well known among dissenters of the process - but what can be done about it.

The three posts that are relevant are ... ... and ... and in the process we get to learn a bit about AE Douglass, 1867-1962, and his research, culminating in the establishment of dendrochronology as a serious dating tool. He was an astronomer and he found a correlation between trees and the sun spot cycle. Douglass went on to to track tree rings in the past and used beams in old buildings and long lived trees such as sequoia. He found tree rings were thinner in some years and there was an effect on them by solar variations - such as the 17th century solar minimum. Subsequently, tree rings have become popular in the study of climate science - where sceptics are rather thicker on the ground than on the dating side of things. Tree rings are not taken seriously by sceptics as narrow rings can occur for a variety of reasons - even the closeness of the tree next to one being measured. However, in spite of this, dendrochronology it is claimed, is now able to date the time when tree rings formed - down to the exact calendar year. 

Cullen says, 'the dark art of dendrochronology is a many headed beast that is based upon two primary assumptions ...'. These are that each year trees create a layer of new wood under the bark and trees of the same species growing at the same point in time, will display a similar trend in tree growth, forming a pattern that can be used wherever a piece of wood is preserved (such as in the fabric of a building). In our neck of the woods, northern Europe, oak trees are used to build up a sequence of tree rings. English Heritage has a web site with quite a lot of information on the use and application of tree rings. It provides a lot of data on the subject otherwise missing from channels open to the general public. Cullen then says the obvious - tree rings are more complex  than dendrochronologists would have us believe. A very narrow ring, for example, is difficult to spot. Wide wood growth in spring could be mistaken for two rings rather than one. Disease and frost may stunt tree growth - and so on. This is mostly obvious and well known to dendrochronologists and their critics. His argument is that in dendrochronology, it is all down to human interpretation - and human misinterpretation. I don't know if he had in mind some of the capers in climate science such as the hockey stick graph or the practise of picking on trees with a desired tree ring width and then going on to ignore its neighbours - which might be saying something entirely different. That is all part of the myth created by climate sceptics - and no doubt there is something to hide otherwise they would be open on their sources.

The weaknesses in dendrochronology go all the way back to original objectives - creating a base line or Site Master (as he calls it) by collecting a sequence of tree rings from a collection of trees of the same species. The Site Master is used to sift new tree rings sequences and computer software has been created to nudge them into a semblance of order - matching the wiggles (or best matching them). He describes the process and then casually informs us there are gaps in the sequences. For example, there are no English tree rings to fill a gap that exists in the 4th century AD. Cullen has tried to get to the bottom of things but claims your average dendrochronologist is sparse with facts - even secretive. They share data between themselves but keep a lid on it as far as the general public are concerned. They have well paid jobs and no clouds on the horizon as far as a career is concerned - unlike many other people, people that are lobbing money out of their pay packets to support funding for the good life they enjoy. This is all reminiscent of the behaviour of climate scientists as revealed in the Climategate Emails - unwilling to share their data with folk outside their little bubble. The extent of manipulation of past climate data by computer programmes designed to favour a warming graph is only now beginning to hit daylight. Jennifer Marohasy, in Australia, has lobbed the latest grenade at the climate science community by showing the process of homogenisation of old data has consistently made temperatures in the past cooler in order to make temperatures in the present appear warmer. Older temperatues are getting cooler and cooler, each month, as the process kicks in. How cool will they end up in ten years time? In spite of all that the temperatures remain flat - in other words, it is cooling. Steve Goddard, a few weeks ago, rattled a few cages in the States by showing the same thing - and drew a lot of criticism upon his head. The facts are that data from the early 20th century is now way below what it was when recorded in official records taken in the field by scientists and their assistants - in the pre-computer era. What do these people think - the world began when computers entered our lives. Their argument is that their homogenisation process, produced by the software they employ, is more reliable than somebody taking a temperature reading in the 1930s. In other words, the fact that it was just as warm in the 1930s as to what it was in the 1990s has been progressively weeded out of the past data used in their modelling of the trend. This is a process that aids and abets global warming. The future trend as churned out by their computer models is on a warming curve and this means they are free to tell the fairy story of global warming that is incessantly poured out upon the ears and heads of Joe Public.

The big question is - why are some dendrochronologists so secretive and act in a manner we may compare to the nefarious variety of climate scientist. Are they part and parcel of the same problem - using tree rings as temperature thermometers when tree rings are defined by all manner of other influences affecting growth and well being.

Tim Cullen points his finger at the 89 year gap during the 4th century AD. Closing this gap - and making it as if it did not exist - would have the effect of omitting a dark age from the history books, the period that is largely a blank between the evacuation of Britain by Rome and the establishment of the Anglo Saxon ruling elite. However, Cullen is more ambitious - he is seeking a 700 year dark age (apparently impressed by Heinsohn's argument). In this he has to get around some well established sequences - and I wish him well.

Later, he homes in on a scarcity of trees to fill a gap in first millennium BC German dendrochronologies. Why are trees scarce at certain points in time? I'm sure Mike Baillie dealt with this anomaly in his book, A Slice Through Time, and it might be worth while to take another look at what he said. See also