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By constructing long tree ring chronologies, using suitable species of trees, it is possible to reconstruct a precisely-dated annual record of climatic conditions.
Ice cores can provide a similar annual record of the chemical and isotopic composition of the atmosphere, in particular volcanic markers such as layers of volcanic acid and tephra.
In this respect, it is extremely unlikely that any of the tree ring data used in this exercise is incorrectly dated. Space analysis demonstrates that while there is a high consistency between phenomena spacing (highlighted in bold), ice core dates are offset by approximately 7 years.
One could also re-examine the hypothesis that frost rings are useful volcanic markers.
A small book describing the process of construction of a tree-ring chronology from scratch till it becomes several-millennia long. chronology, using species growing in aride climates, for which ring width series matching differs substantialy from that for oak. If the rings don't correlate, how can they be used for archaeology?
There are plenty of tree-ring-width graphics comparing two or, usually, more anual tree-ring-width series; describing too how sutiable timbers are seeked for and eventually found (or not), the unexpected outcomes in terms of history of Irish oak forests and other surprises arising from dating of archeological timbers, the two-pass correlation with Germany via England, and more. It is a pity it doesn't include the final linking of the several prehistoric floating chronologies, they were not yet complete at the time of writing. I decided to to a study of tree rings when I read how they supposedly matched up the tree rings from some 8000 year old tree to some dead older tree to extend the timeline to 12,000 years.
In fact, it is possible to have some frost rings without any evidence of explosive volcanism, presumably occurring due to extremes in local weather, but, as shown above, they do seem to record large volcanic eruptions in recent times very well indeed. Furthermore, when a space analysis is performed between historically-dated severe dust veils between the 1st century BC and the 7th century AD, these compare well with frost rings, but again volcanic horizons in Greenland ice appear to be too old by 7-years (see Figure 3).
Accepting, of course, that historical documentation is correct, the dated bristlecone pine frost rings agree perfectly as a response to the volcanically induced climatic events.
In our current paper, we reinforce this proposed re-dating by looking at ice core data published since 2010, from both Greenland (NEEM S1 (Sigl et al., 2013)) and Antarctica (WDC06A (Sigl et al., 2013), Law Dome .
With the proposed re-dating of the ice cores, it now appears that the two massive volcanoes occurred in AD 536 and 540.5, which fits better with a two-stage event.
Figure 4: Greenland ice cores suggesting two large eruptions in AD 529 /- 2 and AD 533.5 /- 2.
This can become difficult since the ice chronologies can only be checked by finding and definitively identifying tephra (volcanic glass shards) that can be attributed to these key eruptions; sulphate peaks in the ice are not volcano specific.
Thus, it is fundamentally important to have chronological agreement between historical, tree-ring and ice core chronologies: The ice cores record the magnitude and frequency of volcanic eruptions, with the trees recording the climatic response, and historical records evidencing human responses to these events. The importance of frost rings An additional piece of evidence is the existence and dating of “frost ring” phenomena observed in bristlecone pines growing at high altitude in Western North America.