Carbon dating is getting a major reboot (2020) | Hacker News Reader

Carbon dating is getting a major reboot (2020)

nature.com

59 pointsrammy123431 comments

Basically, carbon saying sounds like it is counting tree rings:

"Since the 1960s, researchers have mainly done this recalibration with trees, counting annual rings to get calendar dates and matching those with measured radiocarbon dates. The oldest single tree for which this has been done, a bristlecone pine from California, was about 5,000 years old. By matching up the relative widths of rings from one tree to another, including from bogs and historic buildings, the tree record has now been pushed back to 13,910 years ago."

One question, how are they able to push trees ring counting back 13,910 years, if the oldest tree they have counted was 5000 years old. The limit is 5000, right?

And another question, why was this tree only "about 5,000 years old"? They have the very tree, it is either possible to count the rings or not... So why are they rounding (up or down)?

> By matching up the relative widths of rings from one tree to another, including from bogs and historic buildings, the tree record has now been pushed back to 13,910 years ago."

This is exactly how they did it.

edit: Imagine I have one 50 year old tree in the yard, and a house with a log in it that was cut 40 years ago from another 50 year old tree. They were both alive at the same time for 10 years. The relative thicknesses of the rings will match for the first 10 years of the tree and the yard and for the last 10 years of the log in the house, giving me a 90 year record.

Well, if you say so! But its a bit open to interpretation I would say!

Are there that many trees from 10,000 years ago even around, so we can read their rings?

Yes, of course it is subject to interpretation, but it is not the only source of truth.

And no we don't have a vast quantity of 10,00 years trees but enough to be meaningful. We are not measuring in very precise years the further back we go.

They’re in bogs and historic buildings.

This is how the curve looks like for the curious [1]

[1] https://en.wikipedia.org/wiki/Radiocarbon_dating#/media/File...

I thought I had seen the limits of the absurdity of this "footnote style" hyperlinks in HN. Now I'm certain of it.

Fair point :D I did it without much thinking but it certainly looks silly if I look at it now.

for real pretentiousness, it would be numbered from [0]

You're on a forum with a bunch of programmers and other computer people. It's not pretentious to number things the way that we number everything else.

What do you mean?

My guess is that replacing the two [1] with a : the end result would have been the same.

I wouldn't suppose that's meant to be taken personal.

It would be highly pretentious, I think you agree, if it were a normative standard. That's not the case, so it seems they got carried away in trying to be witty

It's a personal peeve, but I find the footnote style of putting in links, rather than inline like the web was intended, to be not only hard to read, but quite pretentious.

These are comments on some web resource, not research papers.

I don't see how it can be pretentious. Usually, I do it to avoid disturbing the flow of text reading.

To each their own I guess. But from another thread today, I'd much rather read https://news.ycombinator.com/item?id=29955514 than https://news.ycombinator.com/item?id=29955106

I guess there's no accounting for taste.

(Or, perhaps meta:

I'd much rather read [1] than [2]. Too much bouncing around; I'm not even sure if it's worse when the text is large compared to the research paper citations, or small.

[1] https://news.ycombinator.com/item?id=29955514

[2] https://news.ycombinator.com/item?id=29955106 )

For my part I much prefer your second variant here, especially when the URL has a long path or query string.

HN doesn't allow inline links like the web intended. So you either get footnote style or the raw link text (possibly with non-human-interpretable query parameters), and either way is hard to read and interrupts the flow of the text.

These curves are still somewhat fragile. I remember reading that the air polution is difficult to predict, so there are big error margins and further updates keep being worked on.

2020

Does anyone else feel that the understanding of historic levels of atmospheric carbon are based on an set of assumptions that are bordering on farcical in the amount of guesswork they require?

You do know that atmospheric carbon level estimation is completely orthogonal to carbon dating, yes?

Carbon dating is about matching radioactive carbon contents in organic matter to samples from trees or other known-age organic matter. As such, it has a limit of ~50,000 years ago.

Historic levels of atmospheric CO2 is mainly based on samples of gas trapped in ice sheets, or estimates based on carbon quantity in mineral sediments that would have absorbed atmospheric carbon in their formation. As such, estimates go back to the entire history of the Earth.

Especially for recent history, where we have bubbles of air from those times still trapped in Antarctic ice, I see this is a remarkably direct measurement, the very opposite of a "farcical amount of guesswork". If we're talking about 1 billion years ago, I start to agree with you a little more.

but what if there was a time when the ice in Antarctica melt? wouldn't it mean that we don't know when and how long it happened and anything about it's atmospheric contents

The temperatures required to melt the ice in a short timespan, and then the temperatures required to re-freeze it in a short timespan after that, would leave marks in other places in the world as well.

We also know for sure that such extreme events have not happened in recorded history, so at the very least you can trust the method for atmospheric carbon content in the last few thousand years - more than enough to prove man-made as the only explanation of these carbon levels, and to compare for climate effects.

Guesswork?

Atmospheric carbon levels are irrelevant to this. C14 date calibration is about the *ratio* of C14 to C12 and C13, not the absolute quantity. Biological processes to not meaningfully select between the isotopes of carbon, anything that grows while exposed to the atmosphere will contain carbon in the same ratio as the atmosphere--but over time the C14 decays, the ratio shifts. That tells you how long since it grew.

(Note the "exposed to the atmosphere" provision--one of the arguments the creationists love is to cite some examples of living organisms that date old. They didn't run the test for giggles, but rather to examine the environment in which the organism was found. Pull something out of a deep cave, date it and you now know how fast the air is exchanged between that location and surface atmosphere. This is because virtually all C14 is created by high energy particles hitting the upper atmosphere.)

A “feeling” does not cut it.

I can assure you that when these theories were put into the test, they were challenged, again and again, and yet they are still standing.

So you need to bring something more on the table rather than just a “feeling”.

Go do the work required to disprove the scientific consensus.

Thanks for the answers, everyone. It was an innocent question, but it seems to have angered people.

Are you serious? Why do you think that?

Yes, I do too. But I also think that’s true for a lot in science. But try and dare scientific “discoveries” in most circles…

I guess it’s also the media’s fault, which cannot properly report on scientific papers. For example, probabilities become factual statements. Because it sells better like this.

Care to make an accurate, precise critique? Because that's the kind that makes science tick, and the type that scientists take seriously.

How do you account for science making accurate predictions about reality?

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