Bishop Hill Wrong-speed dating
Sep 9, 2015 Climate: carbon budget ;)
Last year I posted a series of articles about statistical issues surrounding radiocarbon dating, a subject that is important in its own right but also directly impinges on the climate debate because of the way in which it informs our knowledge of past climates and the carbon cycle.
However, it looks as though a new paper in Earth and Planetary Science Letters is going to extend the debate still further, arguing that radiocarbon dating falls down badly in samples that are over 30,000 years old. According to an article in the South China Morning Post,
In the new study using samples taken from Xingkai Lake near the Sino-Russian border in Heilongjiang province, the scientists used both radiocarbon dating and another method known as optically stimulated luminescence.
Using light to measure the amount of free electrons trapped in quartz, the team was able to tell how long the samples had been kept away from sunlight, and therefore estimate when it was that they first fell in the lake.
By comparing results from the two methods, they found that carbon dating became unreliable beyond a range of 30,000 years.
A word of caution is due: there is no obvious sign of the paper at the journal's webpage and I haven't been able to locate it by a quick Googling. Perhaps we should wait until we have a copy before getting too excited.
Reader Comments (21)
This it?
What's important here is that it indicates the level of C14 was higher in the past. That in turn suggests either that there was more C14 being produced OR that we currently live (i.e. last ~30,000 years) in a period where natural fossil carbon is being emitted into the atmosphere to reduce the amount of C14 compared to periods more than 30,000 years ago.
So, this seems to indicate that either there are massive (unknown) sources of CO2, or that cosmic ray/solar activity changed dramatically. Either or which occurred near the end of the last ice-age ... so there is a strong suggestion they may be related to changing temperature.
Just to recap: C14 measurements are based on carbon that has been irradiated and changed from C12 to C14 in the atmosphere. This is then absorbed by plants as CO2, the plant are then eaten and as a result we all have a level of C14 similar to the level in the atmosphere. When we die, the C14 slowly decays so that the ratio of C14 changes. This rate is constant, so the final ratio depends this time and the ratio of C14 in the atmosphere when the animal/plant lived.
If the specimen appears to be younger than it is, then this shows there was higher ratio of C14 in the atmosphere when the original plant from which the carbon derived lived.
Should have also mentioned that as well as solar and cosmic ray levels, potentially a large change in earth's magnetic field could affect the ray cosmic rays enter the atmosphere and hence the level of C14.
OSL is amazing - it is the method by which the footprints at Happisburgh (Norfolk) were dated to 900,000 years old a couple of years ago. Interesting to see it used as a control for C14.
You take the South China Morning Post? Kudos to your newsagent.
It seems no straw passes unclutched here.
While quartz thermoluminescence dating works fine on ceramics, it proved far less reliable in dating rocks - independent studies could not reproduce what Indian scientists reported a half century ago , as background radiaton and self-irradiation by potassium 40 interfere , as reported by Costas Christodoulides and K.V. Ettinger:in
Some problems of long range thermoluminescent dating as applied to meteorites and tektites
Physics of the Earth & Planetary Ineriors, March 1971 . a critique updated by Wei Da Wang in 2007
If the Hockey Team get hold of this, they will finally admit the Medieval Warm Period happened, but it was last week, and only lasted a few days.
what a surprise! Thirty thousand years is nearly 6 half-lives for C14. No wonder it's unreliable after so long - there isn't much left.
"what a surprise! Thirty thousand years is nearly 6 half-lives for C14"
six half lives = 1.5% or 1500ppm and what exactly is all the global warming hysteria about? A change of 0.4%
I agree with Billy, six half lives infers less than 2% remains of a very small fraction to begin with.
Welcome back Texas Housewife:
"You take the South China Morning Post? Kudos to your newsagent."
As it happens it was the SCMP that I first became aware of the global warming scare. Around 2005 (might have been before or after) I saw a heading that "2500 scientists agreed that humans were causing dangerous warming", or words to that extent. I was immediately sceptical, because as everyone knows, you don't need 2500 scientists to agree something is happening, you just need evidence that it's happening, and you can't provide evidence/proof that you're right if you're indulging if fortunetelling..
I've spent a lot of time in Texas too, mainly in the Dallas area. Great steaks, my favourite place was Del Frisco's behind The Galleria in Richardson, ambience and food great. Portions, for Texas a wee bit on the small side, you could only get 12 oz steaks or above.
Eh, no; it comes from the absorption of thermal neutrons by N14.
Eh, no; it comes from the absorption of thermal neutrons by N14.
I think that almost all the neutrons escaping from an atmospheric nuclear explosion finish up being absorbed by N14 to produce C14 - hence the big spike in C14 in the late 50's early 60's.
https://www.ctbto.org/fileadmin/user_upload/pdf/Sipri_table12b.pdf
When I was young and C14-dating was fairly recent, it was well understood that its accuracy tailed off with age. Back then it was thought to be a subject for celebration that its accurate range included the period of early agriculture and the earliest civilisations in the Middle East. I'm not surprised that there are questions about its performance at 30000 years ago. On the other hand, if two methods disagree, that of itself doesn't demonstrate which is wrong. Not least because both might be.
The South China Morning Post is my local paper and it so supportive of CAGW I'm surprised the print edition doesn't burst into flames. I have yet to see anything in it that even remotely deviates from the consensus line. I suspect the only reason this paper got a mention is that the authors are (mainly) Chinese - the editor is ex-China Daily.
IIRC, beyond 50,000 years, C14 is unreliable anyway, due to the tiny amount being present.
"If the Hockey Team get hold of this, they will finally admit the Medieval Warm Period happened, but it was last week, and only lasted a few days."
Sep 9, 2015 at 5:43 PM | charlie
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And only took place in Stockport.
Care is required! The paleo-reconstructions showing CO2 variation lagging temperature variation must have been on the wall at many a climate alarmers' brainstorming session on barriers to their faster progress. The MBH hockey stick seemed tailor-made to get rid of the MWP, the Stern report to deal with pesky cost benefit calculations, and so on through the melting Antarctic fiasco, the disappearing pause fiasco, and sundry other pieces of policy-led evidence-making by, or at least on behalf of, the very wealthy and influential climate scare industry.
no doubt many cherished 'settled' science icons will fall in the future
some of them unanticipated
I just think the producers of the 'settled science' propaganda are shameful
and have done great damage to the relationship of science to the public
particularly me
Hang on, what they are saying is that one "time" ruler is wrong because another "time" ruler says so!
"optically stimulated luminescence. " Maybe they use the wrong type of light for the stimulation, maybe the older quartz grains like a more pastel blue than the harsh, nasty purple UV and don't glow so much.
We need a third way, so we can then have 3 different ages, this way we can pick the one that suits our theories best and everyone will be happy.
What little we know of our climate history tends to be a thorn in the multifaceted sides of the climate alarm industry, especially those parts which are at least slightly bothered about intellectual matters. One grand, blanket solution for them is to find that the uncertainties in that history are so great that nothing much can be reliably known about it. Carbon dating today, techniques for the far more distant past tomorrow?