CO2

Actually in f_j's other thread, less-than doubled CO2 co-occured with +3.5 oC on Greenland summit. That is a high ratio, as such things go, so I looked to Greenland 's singular climate to make excuses. Trying to help you here buddy, don't go all zombie on me.

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Things we might discuss here about CO2 and biological carbon cycling, could enter some fun areas even without considering infrared heat trapping. Anyone want that?

 

A new paper in PNAS ‘complains’ that continued fossil-C emissions will spoil 14C dating. I am not impressed, because the ambiguity would arise anyway, even with zero burn.

You need to get into the science for this, and I don’t apologize. Step up, or move along to a more entertaining thread.

14C is produced in the atmosphere when neutrons of suitable energy arrive. Most from the nearest star, although apparently more distant sources can contribute if they are ‘bright’ enough. Gamma ray bursters. Yuck. A lot of neutrons arise from thermonuclear or nuclear explosions in the atmosphere. Which we have pretty much stopped doing. Neutrons have no trouble finding a nitrogen atom, and physics ensues.

The early 1960s peak, shown below, had something to do with stopping that, but mostly it was 90 Strontium. That one goes into your bones, where red blood cells get made. That one you really don’t want. Breathing 14CO2 is surprisingly harmless.

14C goes away by radioactive decay, but its atmospheric concentration has more proximate (and faster) controls. In communication with atmospheric CO2 is the much larger marine CO2 pool. It gets diluted out, and Suess (not the childrens’ book author, the other one) gets the credit. Atmospheric 14CO2 concentrations also go down when you put CO2 in the atmosphere that has little or no 14C. That means many 5730-year halflives old, and fossil C is the thing. If you instead burn a tree, it was built of atmospheric CO2 of the most recent 50 years (depends on your tree of course), so it has very small effect. Burn all the wood formed around 1962 and you might cause a detectable uptick.

Some carbon item from, say, 30,000 years ago has much lower 14C than now. Not because Suess effect, because as soon as it died, it ‘lost communication’ with the atmosphere. This deficit is entirely radioactive decay. Note also therefore, that it makes no difference (for dating old things) how much fossil-C gets added to the atmosphere now or later. The pools have become unconnected. So, radiocarbon dating old things remains as useful as ever.

PNAS article complaint is that fossil-C dilution in the atmosphere, going forward, will make ‘new’ dead items seem older than they are. Yes it will along with Suess, they are additive processes. But Suess is faster. How much so, I’ll have to read the article and hope they go into sufficient depth. But thus apparent ‘oldness’ of newly-deceased carbon happens anyway. Maybe a bit faster because of fossil-C combustion, But I remain to be convinced that this is something to worry about.

In the graph below, I draw straight lines into the past and future. They may not have just the right slope, and actually should be slightly exponential. They are only to illustrate that an item from some time in the past will have the same ‘carbon date’ as an item from some time in the future. Decay in the past, and Suess (mostly) in the future. Neither one is negotiable.

 

I am old enough to have had 1962 Strontium 90 bones. But living bones unmake and remake themselves, so now along with the worlds' other old humans, my bones have essentially been replaced by cleaner stuff.

Y'know how plywood is made? A big lathe unwinds the tree, and the sheet coming out 'goes back through time'

The other thing I want, besides the Picarro that the Iceagenow consortium will buy for me is a plywood mill intaking +60 yr old trees. Should only take a few days to get some 14C wood from early 1960s. It is a unique substrate for science that nobody else is thinking about.

Carbon cycling = fun

 

Now having read the PNAS paper by Graven. I see the author is working on a different expectation for the future Suess effect. That is, in the absence of fossil C dilution of 14CO2, that the Suess effect will hit the 100%modern carbon line and stop exactly there. I can see how that might be the case, and is actually more like Suess first described it.

A steady state develops between 'cosmic' 14C source rate and 14C dilution into the marine pool rate. The presumption is that steady state will be on and remain locked to 100% modern carbon.

I can also see that this would not be the case of transfer of atmospheric CO2 to the ocean proceeds at other than a constant rate. Two factors come to mind, first that oceans are net trapping CO2 from the atmosphere at about 2.5 Pg C y-1. Second, that CO2 would be less soluble in warming surface water (and dissolving is the first step to trapping).

Those two factors seem to go in opposite directions. Thus I would find it difficult to anticipate the future extension of the cosmic +Suess line, with or without added fossil C.

But the study was interesting to read. Author suggests a simple cure to solve the problem. If possible, assure that your potentially thousands-year-old carbon does not have any modern carbon sneaking in. This was always necessary. In fact it came up here about last year in deciding whether recently uncovered high-latitude mosses were really very old.

So, as before 14C dating only works if modern sources can be excluded. Burning fossil C makes the problem more important.

So now ya'll are set to go out and do some 14C dating. When you get to the last step, accelerator mass spectrometry, you're going to be amazed.

 

Once in a while, the terrestrial carbon cycle gets a big bump. You may have heard about the Tunguska asteroid (or comet) that arrived in Russia’s boreal forest in 1908. It was the largest recent ‘infall’, although dispute remains on whether it may have been 30 meters diameter or somewhat smaller. Anyway, nothing on this scale has arrived recently, and we will have much better data about the next one that does.

It flattened about 2000 square kilometers of boreal forest, which represents 0.013% of that forest type across the globe. I have just now put that into my global wood mortality database. You are the first to read (get bored by) the results.

Over those 2000 km2 trees were knocked down, and some near the center were promptly burned. Whichever fate, it was new tree mortality. It a bit more than doubled global boreal forest mortality, that year, in about a minute. No forest clearing, or drought, or evil beetles in other forest biomes have matched that in terms of rate. As a part of the global forest (where some tree always die, and faster in the warmer forests), it increased mortality by about 8%.

If you had been onsite, dead. Infalls of this magnitude are 1/1000 or 1/100 year-1. On average they will not directly affect urban areas, those occupying such a small fraction of the total. But they will affect the carbon cycle, more so closer to the equator where carbon turnover is much faster.

Not trying to scare y’all. The telescope effort to detect ‘threatening rocks’ has improved much in recent decades, while they might wish for a bit more funding (all those Ferraris still need to be bought). The next big infalling rock may have larger effects on the carbon cycle than by blowing out (Chelyabinsk) windows.

I don’t want to incite undue fear; that is the terrorists’ domain. But as poorly as we understand the terrestrial carbon cycle now, a ‘wild card’ could make things worse. Complacency is a choice. Choose widely.

 

For all the many earlier infalls, we know nothing' about carbon-cycle impacts. For this one, only because I ran the numbers. I did so, because later we will talk about tree growth and death and decomposition, in the abscence of extraterrestrial effects. it provides a point for comparison.

 

I think the map @29 would be of most use together with one pf permafrost carbon density. I do not think the latter yet exists. For this I'd nominate Tarnocai (it is somebody's name)

It seems unlikely that the highest carbon pools are at the 'warm edge' of permafrost.

 

Plants take CO2 from the atmosphere by photosynthesis. Plant decomposition reverses this process. When both are in balance (and nothing else is upsetting the cart), CO2 would stay the same. There could be annual cycles, suggesting that photosynthesis and decomposition are somewhat shifted in time. This was Keeling’s first big find.


Both of these (terrestrial) fluxes exceed 60 petagrams C y-1. Bigger than fossil C burn of 10. It is one of those things that can be stated clearly, or somewhat misleadingly.


When you burn a tree, it becomes CO2 today, instead of in 10 (or more) years by decomposition. This is a path (rate) change in current decomposition, quite unlike returning fossil C to the atmosphere.


We know that currently, (terrestrial) photosynthesis is larger than decomposition by about 2 Pg C y-1. Not yet clear why this has become so, but it has the effect of slowing atmospheric CO2 increases.

Plants affect CO2 in another way. Soil, initially, is just big rocks. It becomes smaller pieces by many processes, and plant roots make a very large contribution. Smaller pieces have much more surface area and many rock minerals react with (and consume) CO2, limited by their surface area. This is an indirect effect of plants on CO2.


Plants on land 400 million years ago were nothing like what we see today. Descended from seaweed, they where importantly not tall. A water-filled bag of cellulose cannot become so. But plants did diversify, and (apparently with the help of fungi) made roots, and greened up the place from about 400 to 350 million years ago, the first feature.


As an aside, I note that 400 Mya was the beginning of ‘anything of note’ happening on land. Microbes arose between 2 and 2.x billion years ago (at sea) and that was the only place you would find ‘biology’ for 90% of the earth’s history.


Next step, 350 Mya, plants make lignin to get tall and actually competent to move water to heights. I regard this as the most important (terrestrial) biological event of all time. These early trees are not what we know today. They somehow resisted decomposition (for a while) and that lead to coal. First idea was that they grew in flooded land, where fallen wood could not decompose. This is OK, except plant roots also need oxygen, and few are able to grow in flooded soils. Fossils don’t show that trees of that time had such fancy roots. Recently we have learned that fungi able to decompose lignin did not develop until 300 Mya. This corresponds to the end of the ‘coal age’. During the interval from 350 to 300 Mya, atmospheric CO2 dropped massively, and O2 increased (not shown here). The ‘decomposition gap’ from 350 to 300 Mya is the second feature.


Another aside: gymnosperms are trees like pines and firs. Their ancestors played some minor role during the ‘decomposition gap’, but mostly it was trees that are no longer with us. Angiosperms are plants like oaks, wheat, and roses. They came along much later.


The cumulative crash of CO2 by 300 Mya co-occurred with global glaciation. Land plants had made a big mistake! CO2 rose again (probably the ocean’s doing) by 290 Mya and the glaciers went away. All of that will make no sense to folks who resist the heat-trapping role of CO2 in the atmosphere.


Increased CO2 from 280 to 200 million years ago (so far) seems to resist any explanation related to land plants. This period also included ‘the rise of dinosaurs’. We’d want to understand that better, even though ‘that earth’ was different that the one we inhabit now. In the oceans, maybe not so different. Anyway, it is the third feature.


Gymnosperms as we know them now were diversifying and spreading from 180 to 160 Mya, They were decomposable (fungi previously having learned the ‘lignin trick’), But their roots were increasing the surface area of rock bits. Biology and geology, working together. This is the fourth feature.


From 160 to 110 Mya, CO2 was mostly up. As with all the ‘ups’, it resists any explanation related to land plants. We were still in the midst of dinosaur time.


From 110 to 40 Mya was the last large ‘CO2 crash’. Now we have come so far forward that the fossil record greatly improved, and it says angiosperms did this. Diversity of these plants was unlike anything previous. Their roots were increasing rock surface area like crazy. Decomposer fungi should have been able to ‘keep up’, but I guess fungi were simply overwhelmed. This is the fifth feature.


In the midst of that, an upward bump from 90 to 80 Mya. Terrestrial biology offers no help here.


The last biological feature corresponds to evolution of ‘C4’ grasses. They have a physiological trick to prosper at lower CO2 than their fellow angiosperms had ever seen. Also good under water limitations, anyway, this was their starting time and CO2 also decreased. Sixth feature.


This is my view of CO2 history, emphasizing biology. It is incomplete because geological processes varied in their delivery of ‘CO2 hungry’ minerals to atmospheric contact. Continents moved around (really, more than you might imagine) and that must have altered how ocean currents affected interactions with the atmosphere.


It is more incomplete because proxies of 400 Mya are much less informative than those of 40, and 4 Mya. It does not matter what question you ask of the proxies, the veil of prehistory is a real thing.


Plants, gotta love ‘em, but they seem to shoot themselves in the foot (root). Decrease CO2 and ‘hope’ that somebody else fixes it. For me, the cumulative effect of plants on atmospheric CO2 is to reduce it until glaciations become painfully frequent (see the recent 4 million years). Only now have humans corrected this by re-liberating really old CO2. It is an obvious good thing to avoid future ice ages with +CO2. How hot we wish to make it with more CO2 is a whole ‘nother matter, That is what we argue about. A lot.


Here I have only touched on the earths’ fascinating CO2 history.


The picture is from Royer et al. 2004; I added the 1 through 6.

 

Bob @35, stem and leaf imprints in coal are consistent with, but do not prove a 'fungal decomposition gap'. They were long interpreted as indicating underwater, thus anaerobic limitations on decomposition. The latter is required to get those monster dragonfly fossils in coal you have seen. Fungi are not needed to decompose insects. Bacteria have plenty of good 'nuff enzymes. So, some coal certainly had a subaquatic origin.

There are more recent coals; 40% have been formed more recently than 300 Mya. The more recent coals contain fungal microfossils, absent from the older ones. This was the first evidence for 'fungal decomposition gap'. Floudas' enzyme molecular clock evidence was much more convincing.

Please take another look at those percentages. 60% of coal in 50 million years. 40% of coal during the more recent 300 My. That tells you that something important was different. About 9-fold different..

Nowadays about 5 Pg C y-1 comes from wood decomposition. Sounds appealing to slow that down eh? Well, you could just kill the fungi, but seems unwise. Most things that kill fungi are also tough on us. Both being eucaryotes and all.

Or, you could bury or sink a lot of wood. Proposed in the literature. The machinery required ($$ and carbon cost) has not been estimated though. I'm guessing it would be substantial. Plus people want to do things with wood. Paper and building things. That is now about 2 Pg C y-1, and represents in itself a lot of $$. An effort to put wood in a lockbox would not be universally popular.

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Each of the large, steep 'drawdowns' shown above is larger than the CO2 present then in the atmosphere. Mass of the atmosphere being pretty well known, then a bit of math. I find that amazing, and suggestive that volcanic exalation of CO2 were also involved, over multi-million year time scales.

So you got plants trying to kill themselves and volcanoes trying to save everybody. It's quite a strange planet upon which we have so recently 'arrived'.

 

And then there are infalling space rocks. See Tunguska, Siberia, 1908. Heard of it? About 2000 square km of boreal forests blown to the ground. In terms of tree mortality, it is beyond compare in known history. Really under-studied! Remote, I grant you, but it is on my bucket list as a dead-wood enthusiast.

In terms of global tree mortality it bumped that year to 120% of average. Sounds small, because even now, the global forest is big. Another first for PC; sneak preview of my wood-decomposition review.

Eye-glazing over may commence.

 

Last one for now, and not directly related to carbon. Before 400 Mya, river courses ran a particular way. Geomorphologists know this somehow. More recently there have been live rooted trees and logjams and now river channels are different. Except in deserts lacking trees. Those still go as in the olden days.

There is also a huge positive biodiversity effect from having dead wood in forests. Three books about that, and hundreds of published papers. Dead wood in rivers does a whole 'nother biodiversity thing. A small fraction of dead wood escapes to the sea, where 'rafts' allow critters access to remote islands.Marine wood that sinks provides steppingstones for microbes, from one geothermal vent to another.

Combine these things with the CO2 (and oxygen) effects above. That is the package. The evolution of wood massively changed the earth. You have heard that we are now in the 'Anthropocene', where humans call the shots. OK, but for 400 My earth has been in the 'Xylocene'. Almost entirely unrecognized. PC readers get to know. Lucky. Eyes are still glazed though (I see you )