Unexpected (by me) side-effect of CO2 emissions

Introversion · Jul 25, 2015

Just another unintended consequence, and dog knows, the least of my concerns about rising CO2 levels.

Emissions Threaten Age of Uncertainty for Carbon Dating

truthdig said:
If emissions continue under the now-notorious “business as usual” scenario, then by 2050 a brand-new cotton shirt will have the same radiocarbon-dating age as the cloak worn by William the Conqueror when he invaded Britain in 1066.

...

Radiocarbon dating is a 70-year-old technique now used with increasing precision to date anything once alive from the last 50,000 years. It exploits the natural ratio of two isotopes of carbon in the atmosphere.

Plants, and the animals that eat them, absorb radioactive carbon-14 and stable carbon-12 from the atmosphere in proportions which—except during the atmospheric nuclear weapons tests in the 1950s and 1960s—have not changed much from the Ice Ages to the beginning of the Industrial Revolution.

When the tree dies or the animal becomes old bones, the carbon-14 decays at a predictable rate, and the ratio that remains in the laboratory sample is a measure of the specimen’s age.

But Heather Graven, a lecturer in climate physics and Earth observation at Imperial College London, reports in the US journal Proceedings of the National Academy of Sciences that by 2020, as the fossil fuel emissions mount up, the fraction of carbon-14 in the atmosphere could drop to such a level that carbon-dating could become increasingly uncertain.

King Neptune · Jul 27, 2015

Radiocarbon dating has never been precise and the exchange of carbon in things with carbon from the atmosphere was always one of the reasons why it accuracy was not that good.

morngnstar · Jul 27, 2015

This doesn't really matter. It just means you will get two possible dates for any object, say 2050 or 1066, or 2075 or 500. Chances are, you have some other evidence that allows you to rule out one of those two dates. For example, if the shirt says Nike and has a swoosh, it's from 2050.

blacbird · Jul 27, 2015

For some perhaps useful background: The common, dominant isotope of carbon is carbon-12, which is not radioactive. Carbon-14 (with two extra neutrons in the nucleus) is constantly being replenished in the atmosphere via the interaction of cosmic rays with carbon-12. As every living thing takes in carbon as a natural part of the biologic process, a certain proportion of C14 is part of the carbon budget. But C14 is a small proportion of the total carbon atom population.

When an organism dies, however, the biological input of carbon ceases, and the C14 present decays at its normal rate (I think the half-life of C14 is about 1500 years, but somebody can correct me on that if necessary). Therefore the measurability of C14 to C12 has a limit of some few thousand years, before the remnant C14 is too small to be measured.

All that said, I have to question the conclusion presented in the quoted article. As I said, C14 is constantly being replenished as a small proportion of the C12 atoms in the atmosphere are altered by cosmic radiation. But if the the amount of C12 rises, so should the amount of C14, and therefore the ratio of C12/C14 ought to remain stable. At least that's what my brain tells me, and I didn't drink any Talisker today, either.

caw

morngnstar · Jul 27, 2015

blacbird said:
All that said, I have to question the conclusion presented in the quoted article. As I said, C14 is constantly being replenished as a small proportion of the C12 atoms in the atmosphere are altered by cosmic radiation. But if the the amount of C12 rises, so should the amount of C14, and therefore the ratio of C12/C14 ought to remain stable. At least that's what my brain tells me, and I didn't drink any Talisker today, either.

Sure more C12 will lead to more C14, but not right away. Let's say C14 was in a steady state before man's activities. That means it was being created at the same rate it was being destroyed. We know it would take thousands of years for that C14 to be destroyed. Therefore it must have taken thousands of years to be created. The amount of C14 needed to offset the C12 added to the atmosphere hasn't had time to be created. (Note that this analysis neglects C14 that leaves the atmosphere by the general carbon cycle instead of decay, but my guess is that that also takes at least thousands of years.)

Eventually if the carbon content of the atmosphere reaches a new steady state, the normal isotope ratio will be restored. C12 will be added to the atmosphere at the same rate as it's removed, and so will C14. All these rates are to a first approximation proportional to the concentration in the atmosphere.

blacbird · Jul 28, 2015

morngnstar said:
Sure more C12 will lead to more C14, but not right away. Let's say C14 was in a steady state before man's activities. That means it was being created at the same rate it was being destroyed. We know it would take thousands of years for that C14 to be destroyed. Therefore it must have taken thousands of years to be created. The amount of C14 needed to offset the C12 added to the atmosphere hasn't had time to be created. (Note that this analysis neglects C14 that leaves the atmosphere by the general carbon cycle instead of decay, but my guess is that that also takes at least thousands of years.)

Eventually if the carbon content of the atmosphere reaches a new steady state, the normal isotope ratio will be restored. C12 will be added to the atmosphere at the same rate as it's removed, and so will C14. All these rates are to a first approximation proportional to the concentration in the atmosphere.

The bolded is simply incorrect. By the simplest analogous example, U238 has a half-life of 4.5 billion years. It gets created in a virtual instant via supernova explosion. The latter process is actually true of all the heavier radioactive isotopes. We can artificially create Pu239 in nuclear reactors; Pu239 has a half-life in millions of years. The radioactive decay rate of any isotope has nothing to do with the time it takes to form it.

caw

morngnstar · Jul 28, 2015

It's true under the assumption of steady-state. Steady-state assumptions are often used in atmospheric science, and are justified in this case by the well-supported scientific fact of stable carbon isotope ratios, at least for recent geologic time. A supernova is not a steady state. We know the mechanism of C14 production. It is cosmic rays, which arrive at Earth in a constant flux.

Myrealana · Jul 28, 2015

My father taught us about this in my freshman Earth Science class back in 1984.

blacbird · Jul 28, 2015

morngnstar said:
It's true under the assumption of steady-state.

What is?

For further clarification: Cosmic rays blast the Earth in uncountable numbers every second, in a very steady state manner. A minuscule fraction of those interact with C12 atoms in the atmosphere. If there are more C12 atoms available, more C14 will be created. The increased amount of C12 emitted in CO2 from fossil fuels will, as far as i can discern, simply produce more of the same percentage of C14.

Now, as far as C14 dating becoming impossible by 2020: C14 is used to date, generally, archaeological objects. Those materials aren't going to change, and will continue to be datable by C14 methods.

I once tried to date Yvonne Olson using the C14 method,, back in college, but she would nave nothing to do with it. Or my scientific method.

Carbon emissions, whether they be almost entirely C12 (from fossil fuels which will contain virtually no C14) or from things like forest fires (which will contain the normal ratio of C12/C14, are a problem primarily as they exist in the chemical forms of CO2 and CH4, which are major greenhouse gases. Whether the carbon atoms are C12 or C14 is inconsequential in this context.

CAW

morngnstar · Jul 28, 2015

Hey man, I didn't make it up. I'm just trying to explain it, not defend it. Kind of silly us amateurs arguing over peer-reviewed research: http://m.pnas.org/content/early/201...ract?sid=c4358b82-dac9-419e-a8c2-34ca4d8814b2

blacbird said:
If there are more C12 atoms available, more C14 will be created. The increased amount of C12 emitted in CO2 from fossil fuels will, as far as i can discern, simply produce more of the same percentage of C14.

Eventually.

blacbird · Jul 28, 2015

morngnstar said:
Hey man, I didn't make it up. I'm just trying to explain it, not defend it. Kind of silly us amateurs arguing over peer-reviewed research:[/quote]

Just for your info, I ain't exactly an amateur in this particular field. I'm a Ph.D. geologist and regularly teach about climate, radiometric dating, radioactivity in general, the carbon cycle, etc., in my geology classes. Now, I'm willing to look at the information (which I did), and evaluate it on its merits. But a couple of your comments just rang wrong, and that's what i responded to. in particular the one implying that it takes as long to manufacture a radioactive isotope as it does for it to decay. Those two processes are completely unrelated and unlinked.

In case you missed it, I am by no means in favor of us humans continuing to pour artificial quantities of carbon gases into the atmosphere, which we've been doing for well over a century now. But messing up the ability to carbon-date materials is by far the least of our worries on that front, and I really question, for the reasons I've expressed, even how much that will happen.

caw

morngnstar · Jul 28, 2015

Well this is embarrassing. It seems you and I have been laboring under a misapprehension. C14 is not produced from C12 by cosmic rays in the atmosphere. It's produced from N14 (the normal kind of nitrogen). So increase of carbon in the atmosphere won't increase the rate of production of C14. The quantity of C14 in the atmosphere will remain unchanged, while C12 goes up. I'd say this will produce a permanent (at least as long as atmospheric carbon remains elevated) not transient decrease in the C14 ratio.

blacbird · Jul 29, 2015

Ah! I stand corrected . . . well, perch, actually. This makes more sense, and I learned something useful. Danke.

caw

Alessandra Kelley · Aug 2, 2015

It's not my specialty (fine art major, sorry) and I'm still trying to wrap my head around it, but if I understand correctly, the mass extinction at the end of the Permian Period 252 million years ago -- which was far more severe than the more famous extinction event 65 million years ago which took out the dinosaurs, and which killed off 70% of all terrestrial species and 90% of all oceanic life (including the last of the beloved trilobites) and is the only known mass extinction of insect species and clobbered biodiversity so badly that global ecosystems did not stabilize again for nearly ten million years (there is evidence that there were no stable forests anywhere for up to 5 million years afterwards, and even river systems worldwide changed from slow, lush, meanders lined with vegetation to fast, gravelly braided systems which eroded massive quantities of soil into the oceans, burying offshore ecosystems) -- also coincided with a massive spike in "lighter" C12 which lasted for half a million years and is evident in rock deposits worldwide.

Here's an article about it, rather technical but sobering and interesting: http://www.skepticalscience.com/pollution-part-2.html

It's not entirely clear how such a vast amount of old carbon got into the atmosphere and oceans. There are theories about volcanic eruptions igniting old coal beds laid down in the earlier Carboniferous. However it was done, vast amounts of CO2 containing a much higher ratio than normal of C12 compared to C14 entered the atmosphere in a relatively short time, only a few thousand years for the initial spike (although the high levels of low-weight carbon lingered for half a million years).

We may be doing artificially what bad luck did to the creatures and plants of the Permian.

blacbird · Aug 5, 2015

Alessandra Kelley said:
It's not my specialty (fine art major, sorry) and I'm still trying to wrap my head around it, but if I understand correctly, the mass extinction at the end of the Permian Period 252 million years ago -- which was far more severe than the more famous extinction event 65 million years ago which took out the dinosaurs, and which killed off 70% of all terrestrial species and 90% of all oceanic life (including the last of the beloved trilobites) and is the only known mass extinction of insect species and clobbered biodiversity so badly that global ecosystems did not stabilize again for nearly ten million years (there is evidence that there were no stable forests anywhere for up to 5 million years afterwards, and even river systems worldwide changed from slow, lush, meanders lined with vegetation to fast, gravelly braided systems which eroded massive quantities of soil into the oceans, burying offshore ecosystems) -- also coincided with a massive spike in "lighter" C12 which lasted for half a million years and is evident in rock deposits worldwide.

Here's an article about it, rather technical but sobering and interesting: http://www.skepticalscience.com/pollution-part-2.html

It's not entirely clear how such a vast amount of old carbon got into the atmosphere and oceans. There are theories about volcanic eruptions igniting old coal beds laid down in the earlier Carboniferous. However it was done, vast amounts of CO2 containing a much higher ratio than normal of C12 compared to C14 entered the atmosphere in a relatively short time, only a few thousand years for the initial spike (although the high levels of low-weight carbon lingered for half a million years).

We may be doing artificially what bad luck did to the creatures and plants of the Permian.

All of this is entirely correct, and you get an A in my Physical Geology class.

There's pretty much consensus among geologists that the Permo-Triassic extinction event was generated by the vast outpouring of volcanic material now preserved as the Siberian Traps, and that those, immediately overlying Pennsylvanian-era coal beds, did result in a very large increase in atmospheric CO2. It is estimated to have taken about a million years, overall.

If the present rate of human-caused CO2 emissions continues, we will equal that Permo-Triassic release of CO2 in a thousand years or so. Do the math.

caw

Maxx · Aug 24, 2015

King Neptune said:
Radiocarbon dating has never been precise and the exchange of carbon in things with carbon from the atmosphere was always one of the reasons why it accuracy was not that good.

The measurement is precise. What is imprecise is precisely the relationship of the measurement to time for recent samples. That can be corrected with samples from tree rings and beyond that the error in the measurement is greater than the error in the carbon curves. I was trained as an Archaeologist and the carbon correction from tree rings was good news back in the 1970s. Carbon dates correlated with tree rings can give very accurate dates at least as far back as the big volcanic explosion in the Aegean in the spring of 1628 BC.

Unexpected (by me) side-effect of CO2 emissions

Introversion

Pie aren't squared, pie are round!

King Neptune

morngnstar

blacbird

morngnstar

blacbird

morngnstar

Myrealana

I aim to misbehave

blacbird

morngnstar

blacbird

morngnstar

blacbird

Alessandra Kelley

Sophipygian

blacbird

Maxx

Got the hang of it, here