But that’s all just fine tuning. We see that ignoring those flucuations, because they are small, doesn’t change much.
The goal is to get C14 dates as accurate as possible. That’s what fine tuning does. Even corrections by a few dozen years can change our understanding of how some historical events unfolded. But yes, it doesn’t change the overall big picture much at all.
Well to take @thoughtful’s side here, she did say that she saw a video where some researcher stated that they checked to see if their counting of the layers were correct by carbon-dating them.
Now that does immediately raise a question, what does “checked” here mean, and what did they do if they found a mismatch? The crucial issue, to avoid the charge of circularity, is that they did not alter their layer counts to match the carbon dates, if those same layer counts are supposed to provide calibration for carbon dates in the first place.
So being charitable, perhaps what the researcher in the video meant to say(some people are poor communicators, including scientists), was simply that they compared the two to see if they matched up, without actually altering their counts?
I didn’t watch the video myself, but from what Valerie relayed the researcher said, I can see how that would have appeared to undermine the whole thing.
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I’m asking for the circularity in the days I presented, not the video.
IIRC it is common for dendrochronologists to use C-14 dating to determine which part of the 10ky+ tree-ring record they should attempt to match new samples to, especially when those samples are from long-dead trees or have been extracted from building materials and so it’s not obvious where to start.
I’ve seen this misused to claim that tree-ring / C-14 dating is circular.
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That is not subjective. There is overlap, and the overlapping regions are like fingerprints, they have characteristics which match and identify.
Remember when I posted the verse from “Great is thy Faithfulness”
Summer and winter, and springtime and harvest,
Sun, moon and stars in their courses above,
Join with all nature in manifold witness
To Thy great faithfulness, mercy and love.
The manifold witness of nature to the annual cycle is written in varves in lakes and oceans, ice cores of Antarctica and Greenland, tree rings, cave stalagmites, coral reefs, and they all point to time more distant than YEC allows. If it was just one of these, maybe AiG could mount some sort of strained argument, but all of them together? It is just a matter of counting…1, 2, 3…29978…29979… There is no circular argument to counting.
Nor is carbon dating circular. Carbon dating is based on the laws of physics and measurements of decay - this is not a circular basis. The reason we know about the potential impact of climate change on Carbon dating is because of the extraordinary amount of work invested to further the confidence we have in the technology.
So when carbon dating is applied to countable annual layers, one non-circular technique is confirming another independent non-circular technique. Now, to be sure, these do not always line up exactly, and we use one technique to deepen our understanding of the other, so there is an interplay that goes on there, but when YEC dismisses the entire enterprise as circular, that is rhetoric, not science.
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Even though the new IntCal20 C14 calibration hasn’t been officially released yet the journal Radiocarbon has provided online a dozen or so of the pre-published results.
There are now separate calibration tables for the Northern hemisphere, Southern hemisphere (which differs for technical reasons roughly 35 years off the Northern), and Marine radiocarbon data all extended back from 0 to 55,000 years before present. There is also an interesting cross correlation / verification of the Lake Suigetu varve data set with U-Th dated speleothems from Hulu Cave in China.
Probably TMI for most but it’s interesting to see just how much time and effort and data analysis goes into getting C14 dates as accurate as possible. 
Yes, actually when I saw the video, the “non-scientist” in me said, “they can’t possibly count that” 
So…the “scientist” in me says give it a chance - the whole point of the varves to me, again, is that they are independently and visually counted. That’s what the whole argument falls on. It would be OK to put sections of the one core sample back together, but if you combine one sample with another sample that could result in bias. If they use any other method to place the varves within a certain year time frame, then what’s the point of this argument? It’s not independent any more; it’s circular. It’s fine if you believe evolution is all there is, you’d think you’re making a pretty good argument for radiocarbon calibration. But if I don’t believe in evolution (and I don’t), then the arguments fails for me.
OK - so I tried to do some searching to see what scientists say. I didn’t find anything that immediately jumped out at me. I did find however, that AIG has since responded to an article that one of the graphs the Duff article uses.
To me, it’s a lot of words…and I don’t really care that much about all of them. I wanted to see the original articles. The ones they referenced appear not to be online. However, they did say that scientists did NOT independently count all the varves:
“Second, although the sequence of 29,100 laminae may itself have been uninterrupted, the start date for this varve chronology was uncertain. Hence, the chronology constructed for this varve sequence was a “floating” one (Kitigawa and van der Plicht 1998, 505–506), in which the start date had to be determined by a method other than simple counting.”
And they quote scientists who admit they tused radiocarbon dating for the Steel Lake varves. Admittedly, those are from an earlier time frame (but doesn’t that make it every worse?
“Application of appropriate correction factors to these two intervals results in excellent agreement between the varve and 14C chronologies. These results, together with other varve studies, demonstrate that an independent age-determination method, such as 14C dating, is usually necessary to verify, and potentially correct, varve chronologies . [Emphasis ours]”
So I thought I’d check back to see what the Duff article links to for original data. I found the correct link for Lake Suigetsu publications (they must have since updated the website) http://www.suigetsu.org/publications.html
However, I didn’t spend time checking that out because I found what I needed in the Science and Nature articles linked… well actually the Nature article didn’t refer to any specific details, but this section is quite amusing. 
"The researchers collected roughly 70-metre core samples from the lake and painstakingly counted the layers to come up with a direct record stretching back 52,000 years. Preserved leaves in the cores — “they look fresh as if they’ve fallen very recently”,
https://www.nature.com/news/core-sample-sends-carbon-clock-farther-back-in-time-1.11622
Ah, but the Science article was more revealing. I’ll bold the relevant parts for me. I didn’t even bother reading the whole thing. The first few paragraphs were enough. https://science.sciencemag.org/content/338/6105/370?keytype=ref
Lake Suigetsu contains annually laminated sediments that preserve both paleoclimate proxies and terrestrial plant macrofossils that are suitable for radiocarbon dating. The lake’s potential to provide an important archive of atmospheric radiocarbon (14C) was realized in 1993 ( 1 ). However, the single SG93 sediment core then recovered included missing intervals between successive sections ( 2 ). This, together with the difficulty of visual varve counting, resulted in inconsistency between the SG93 and other 14C calibration records ( 3 ). The SG06 core-set recovered in 2006 consists of four parallel cores that together avoid any such sedimentary gaps ( 4 ). Here, we report 651 14C measurements covering the period between 11.2 and 52.8 thousand years before the present (kyr B.P.) tied to a time scale derived from varve counting and temporal constraints from other records. Using visual markers, we applied a composite depth (CD) scale to all cores, including SG93. We also define an event-free depth (EFD), which is the CD with substantial macroscopic event layers (such as turbidites and tephras) removed.
Accelerator mass spectrometry radiocarbon dating ( 5 ) has been conducted on terrestrial plant macrofossils selected from the SG06 cores to cover the full 14C time range, from the present to the detection limit of the 14C method (0 to 41 m CD) (table S1). The results already reported from the control period (0 to 12.2 kyr B.P.) ( 6 ), covered by the tree-ring–derived calibration curve ( 7 ), act to demonstrate the integrity of the sediments and to anchor the floating SG06 varve chronology, because varves do not extend into the Holocene.
Note this graph only looks so impressive because the x-axis is so compressed. Imagine what it would look like if you stretched it to be 100 times longer?
The x axis is exactly the same in terms of years as the y axis. Nothing is compressed, it is symmetrical, hence the 45 degree slope. Why would you choose differing scales?
What I find notable, especially for the first 30,000 year stretch, is the tight correlation.
Why in the world would you want to stretch the X-axis to be 100 times longer??? It’s a 1:1 graph showing measured C14 time vs. calibrated C14 time. C14 dating is only used for dates back to 50,000 years, although the IntCal20 data will extend that back to 55,000 years.
Do you have any comments on all the other independent yearly proxies besides the Suigetsu varves which are used for the calibration? Did you see my post just above where the Suigetsu varve dates have been independently verified by a completely different method using speleothems from the cave in China?
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Why do you find it relevant that the four SG06 cores were parallel?
That makes no sense. Both axes are measured in years; they have the same scale. If you stretch one, you should stretch the other and you get the same graph (just magnified).
Note also that all the data sets are basically piled up on top of each other, although they are slightly off the 1:1 line. All this indicates is that the “conventional” C14 age needs calibration, which we already know.
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It would be even more impressive because it’d cover a whole wall - but then we’d just shrink it again to fit on the screen.
You are expanding the y-axis too, right?
My comment here:
Um, do know what the word parallel means?