CO2 Residence Times, Ocean Levels What Next?

[Saul]

I have been reading through some of the older papers concerning CO2 levels in the 20th and century, CO2 residence times, and the carbon cycle. (The papers this linked to article and paper are referencing. Another source is the 2300 papers Ian Plimer references in his book Heaven and Earth.) What I found is interesting.

CO2 Residence Time, Source of 20th Century CO2, Could CO2 levels start to drop? Why did the Ocean level increase in the 20th century? Could ocean levels drop?

If the residence time for CO2 in the atmosphere is short, then the majority of the 20th century CO2 increase does not have to be anthropomorphic. Did anything changed in the 20th century that could have increase CO2 in the atmosphere? If that hypothesis were correct, then if the forcing function that increased CO2 in the 20th century diminished, CO2 levels could drop or at least stop rising. i.e. The CO2 levels in the atmosphere could be delinked from anthropomorphic emissions.

http://www.co2science.org/articles/V12/N31/EDIT.php

Because of the argument going on about global warming people are caught up with arguing one side or the other, which makes it difficult to see or discuss the problem situation.

There are multiple paradoxes associated with the paleo climatic data, the geological data, and the current observations that appear logically connected.

One of the puzzles to explain is why in the past have CO2 levels increased and decreased. Another is why ocean levels have increased in decreased in the past.

A basic analysis shows the Himalayan/Tibet plateau hypothesis does not explain the reduction in CO2 in the Cenozoic. There is obviously something that resupplies a form of carbon to the atmosphere. The question is what stabilizes the amount of CO2 in the atmosphere. A short residence time for CO2 allows the 80 times atmosphere CO2 in the oceans to buffer changes to help regulate the amount of CO2 in the atmosphere so it does not fall to dangerously low levels.

Something else is regulating the amount of CO2 in the atmosphere. Something else is controlling amount of carbon that is released into the atmosphere. As noted in the Sloan Deep Carbon there is evidence immense inputs of C12 rich carbon into the planet.

If you look at paleo data for the last 500 million years. The planet cools, ice sheets form and then after the ice sheets form the CO2 level drops.

 

[Skyhunter]

Saul you need to provide a credible reliable source for discussion.

Blogs are not credible sources for this forum.

 

[Saul]

Saul you need to provide a credible reliable source for discussion.

Blogs are not credible sources for this forum.

This paper supports the blog. If do not have a scientific comment, please make no comment.

What Caused the Glacial/interglacial atmospheric pCO2 cycles?

http://www.cgd.ucar.edu/tss/staff/mahowald/papers/archer2000.pdf

Fifteen years after the discovery of major glacial/interglacial cycles in the CO2 concentration of the atmosphere, it seems that all of the simple mechanisms for lowering pCO2 have been eliminated. We use a model of ocean and sediment geochemistry, which includes new developments of iron limitation of biological production at the sea surface and anoxic diagenesis and its effect on CaCO3 preservation in the sediments, to evaluate the current proposals for explaining the glacial/ interglacial pCO2 cycles within the context of the ocean carbon cycle.

After equilibration with CaCO3 the model is unable to generate glacial pCO2 by increasing ocean NO3 but predicts that a doubling of ocean H4SiO4 might suffice. However, the model is unable to generate a doubling of ocean H4SiO4 by any reasonable changes in SiO2 weathering or production. Our conclusions force us to challenge one or more of the assumptions at the foundations of chemical oceanography. We can abandon the stability of the “Redfield ratio” of nitrogen to phosphorus in living marine phytoplankton and the ultimate limitation of marine photosynthesis by phosphorus. We can challenge the idea that the pH of the deep ocean is held relatively invariant by equilibrium with CaCO3. A third possibility, which challenges physical oceanographers, is that diapycnal mixing in ocean circulation models exceeds the rate of mixing in the real ocean, diminishing
the model pCO2 sensitivity to biological carbon uptake.

 

[Skyhunter]

That paper does not support a short atmospheric residency for CO₂.

You are attempting to put forth a specious argument picked up on a denier blog.

And that is against forum rules.

 

[Saul]

That paper does not support a short atmospheric residency for CO₂.

You are attempting to put forth a specious argument picked up on a denier blog.

And that is against forum rules.

Stop posting and either read the paper or stop commenting. The blog specifically reference papers that show a short resident time. A short residence time is not controversial.

You are not thinking about the problem situation. The paper I quoted above shows there is no explanation for the drop in CO2 levels during the glacial phase.

The additional CO2 that cold water can hold cannot possible explain the drop of CO2 during the glacial phase. Vast areas of the ocean are covered with ice so that water cannot exchange CO2. During the glacial phase the biosphere shrinks. Vast areas are covered with ice and hence cannot support life.

When the planet is colder it is also drier. Deserts increase in size. Almost a 1/2 of the Amazon forest becomes grassland which is as we are aware of, not a good CO2 sink. CO2 should have increased not decreased during the glacial phase.

 

[Skyhunter]

Stop posting and either read the paper or stop commenting. The blog specifically reference papers that show a short resident time. A short residence time is not controversial.

If David Archers paper supports a short residency for CO₂, then please point it out.

As for short residency being non-controversial?

http://www.globalwarmingart.com/images/4/48/Carbon_Dioxide_Residence_Time.png

BTW, the chart above is within the parameters of http://geosci.uchicago.edu/~archer/reprints/archer.2005.fate_co2.pdf"

You are not thinking about the problem situation. The paper I quoted above shows there is no explanation for the drop in CO2 levels during the glacial phase.

Actually their conclusions are that none of the explanations fit the data well, not that there is no explanation. They never made any such claim that CO₂ must have a short atmospheric residence. In fact, five years later David Archer published another paper that reached the exact opposite conclusion.

 

[Saul]

If David Archers paper supports a short residency for CO₂, then please point it out.

As for short residency being non-controversial?

Skyhunter,

You do understand the problem situation. Archer and others are arguing for a resident time of a 1000 years, while the previous papers argued for a residence time of 5 to 7 years. That is an astonishing large change in residence time.

It is controversial to argue for a 1000 year residence time because a 1000 year residence time cannot explain how the planet has responded to the high C14 created by atomic testing or to CO2 spikes produced by super volcanoes. (i.e. The glacial phase was not interrupted when there is a CO2 spike.)

The CO2 spikes are smoothed in the past as the ocean CO2 sink is 80 times the size of the amount of CO2 in the atmosphere. 80 times atmosphere is a very large number. If the residence time is not a 1000 years, but rather 5 to 7 years it becomes very difficult for a spike in CO2 to change the 80 times atmosphere reservoir.

The "blog" is written by the author of the published paper. Of course do not listen to the logical arguments that author presents. As I stated you appear to be not interested scientific discussion. You just appear to want to interrupt this thread.

I am of course interested in the practical implications of the two hypotheses.

If the residence time for CO2 is short say 5 to 7 years, then the CO2 rise in the atmosphere must be due to some other mechanism.

Did anyone have a look at the Sloan Deep Carbon seminar information?

 

[Xnn]

Saul;

If you could find a peer reviewed science article that has determined a shorter residence time for CO2, then that would be a good starting point. Otherwise, we are left with what the IPCC has concluded is the state of the science regarding the subject; namely that the residence time for CO2 is long enough to be a concern.

On the other hand, we know that CO2 levels have not been constant throughtout Earth's history. Some of the mechanisms (besides volcanonism and weathering of rocks) that are thought to be a factor in the past (but not now) are methane calthrates and anoxic conditions in the artic ocean.

Methane calthrates are thought to have caused the significant rise in CO2 that led to the Eocene optimum. They are deep in the ocean and only come into play when ocean temperatures rise significantly. Right now, they are stable.

An anoxic arctic ocean is thought to have caused the significant decrease in CO2 that led to the glaciation of antarctica. Ordinarily, the oceans does not sequester carbon efficiently since it is oxidized into CO2 so easily. However, if enough freshwater covered the arctic ocean, then it there could be an oxygen poor layer along the bottom that could allow carbon to be sequestered.

I believe the 2 mechanims desribed above are not normally thought to be part of the carbon cycle, but have come into play in the past and could in the future as well.


http://en.wikipedia.org/wiki/Azolla_event

 

[Saul]

Saul;

If you could find a peer reviewed science article that has determined a shorter residence time for CO2, then that would be a good starting point. Otherwise, we are left with what the IPCC has concluded is the state of the science regarding the subject; namely that the residence time for CO2 is long enough to be a concern.

Ian Plimer has a number of papers referenced in his book. I will see what I can find.

 

[Saul]

The atomic testing produced C14 supports a retention time of around 4 years. There is suggestion in IPCC literature of a retention time of 4 years to 200 years. There is a recent published paper that is suggesting retention time of 1000 years. These long retention times seem physically impossible based on the C14 retention time which is in accordance with basic physical principles of equilibrium of gas in a liquid. (CO2 is absorbed and released in the ocean. So the ocean equalizes the ratio of CO2 in the atmosphere and the ocean.)

http://climateresearchnews.com/2009/08/atmospheric-residence-time-of-man-made-co2/

Atmospheric Residence Time of Man-Made CO2
Potential Dependence of Global Warming on the Residence Time (RT) in the Atmosphere of Anthropogenically Sourced Carbon Dioxide

Robert H. Essenhigh
Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio 43210
Energy Fuels, 2009, 23 (5), pp 2773–2784
DOI: 10.1021/ef800581r
Publication Date (Web): April 1, 2009
Copyright © 2009 American Chemical Society

The driver for this study is the wide-ranging published values of the CO2 atmospheric residence time (RT), τ, with the values differing by more than an order of magnitude, where the significance of the difference relates to decisions on whether (1) to attempt control of combustion-sourced (anthropogenic) CO2 emissions, if τ > 100 years, or (2) not to attempt control, if τ 10 years. This given difference is particularly evident in the IPCC First 1990 Climate Change Report where, in the opening policymakers summary of the report, the RT is stated to be in the range of 50−200 years, and (largely) on the basis of that, it was also concluded in the report and from subsequent related studies that the current rising level of CO2 was due to combustion of fossil fuels, thus carrying the, now widely accepted, rider that CO2 emissions from combustion should therefore be curbed. However, the actual data in the text of the IPCC report separately states a value of 4 years.

Comment: There appear to be a new paper that is proposing a CO2 retention time of 1000 years.

The differential of these two times is then clearly identified in the relevant supporting documents of the report as being, separately (1) a long-term (100 years) adjustment or response time to accommodate imbalance increases in CO2 emissions from all sources and (2) the actual RT in the atmosphere of 4 years. As a check on that differentiation and its alternative outcome, the definition and determination of RT thus defined the need for and focus of this study. In this study, using the combustion/chemical-engineering perfectly stirred reactor (PSR) mixing structure or 0D box for the model basis, as an alternative to the more commonly used global circulation models (GCMs), to define and determine the RT in the atmosphere and then using data from the IPCC and other sources for model validation and numerical determination, the data (1) support the validity of the PSR model application in this context and, (2) from the analysis, provide (quasi-equilibrium) RTs for CO2 of 5 years carrying C12 and 16 years carrying C14, with both values essentially in agreement with the IPCC short-term (4 year) value and, separately, in agreement with most other data sources, notably, a 1998 listing by Segalstad of 36 other published values, also in the range of 5−15 years.

IPCC 2001 estimates the CO2 retention time in the atmosphere to be 5 year to 200 years.

That is a very wide range, a factor of 40.

http://www.ipcc.ch/ipccreports/tar/vol4/index.php?idp=86

 

[Xnn]

Here are some excerpts from the IPCC technical summary
document concerning carbon residence.

• Positive feedback
• Significant uncertainty
• More acidic oceans
• 30,000+ years to equilibrium
• 1000+ years committed climate change

TS.5.4: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf

all models that treat the coupling of the carbon
cycle to climate change indicate a positive feedback
effect with warming acting to suppress land and
ocean uptake of co2, leading to larger atmospheric
co2 increases and greater climate change for a given
emissions scenario, but the strength of this feedback
effect varies markedly among models.

however, there are still
significant uncertainties due, for example, to limitations
in the understanding of the dynamics of land ecosystems
and soils.

increasing atmospheric CO2 concentrations lead
directly to increasing acidification of the surface
ocean. Projections based on sres scenarios give
reductions in ph of between 0.14 and 0.35 units in the
21st century (depending on scenario), extending the
present decrease of 0.1 units from pre-industrial times.

the slow long-term buffering of the ocean,
including caco3-sediment feedback, requires 30,000 to
35,000 years for atmospheric CO2 concentrations to reach
equilibrium. Using coupled carbon cycle components,
EMICs show that the committed climate change due to
past CO2 emissions persists for more than 1000 years, so
that even over these very long time scales, temperature
and sea level do not return to pre-industrial values.

An indication of the long time scales of committed climate
change is obtained by prescribing anthropogenic CO2
emissions following a path towards stabilisation at 750
ppm, but arbitrarily setting emissions to zero at year 2100.
In this test case, takes about 100 to 400 years in the
different models for the atmospheric CO2 concentration to
drop from the maximum (ranges between 650 to 700 ppm)
to below the level of two times the pre-industrial co2
concentration (about 560 ppm), owing to a continuous but
slow transfer of carbon from the atmosphere and terrestrial
reservoirs to the ocean

 

[Xnn]

The atomic testing produced C14 supports a retention time of around 4 years. There is suggestion in IPCC literature of a retention time of 4 years to 200 years. There is a recent published paper that is suggesting retention time of 1000 years. These long retention times seem physically impossible based on the C14 retention time which is in accordance with basic physical principles of equilibrium of gas in a liquid. (CO2 is absorbed and released in the ocean. So the ocean equalizes the ratio of CO2 in the atmosphere and the ocean.)

"Retention time" derived from atomic weapons testing is physically not the same thing.
Weapons testing released relatively small amounts of radioactive carbon into the atmosphere. It takes only a few years for these radioactive components to diffuse thru the biosphere and reach equilibrium. The amount of carbon released is so small that it has negligible impact on the pH of the oceans or the climate. So, the only thing being measured by tracking radioactive carbon is the diffusion time.

With climate change, we are concerned with the release of gigatons of CO2. Over the long term, these emission result in a warmer and more acidic ocean, which in turn is less able to absorb CO2. Likewise, warmer land temperature influence the carbon cycle due to biological changes of the soil.

So, with respect to the impact of the climate, the concern is how long it takes to reach biological and chemical equilibrium with the emission. The IPCC is currently looking at 30,000+ years for CO2 to reach chemical equilibrium and 1000+ years of committed climate change. These values are large due primarily to the depth of the oceans.

 

[Saul]

Xnn,

This is a list of the papers that discuss retention time.

http://c3headlines.typepad.com/.a/6a010536b58035970c0120a5e507c9970c-pi

I think the discussion has moved from CO2 absorption times in the ocean which we agree is around 5 years to the ocean's ability to regulate CO2 in the atmosphere.

Another approach to understanding the CO2 regulation problem situation is to examine all of the unexplained CO2 regulation and CO2 levels in the atmosphere problems together.

Look for a solution that solves all puzzles. Akin to suggesting tectonic plates move to provide a solution to the set of geological surface puzzles.

Puzzle 1
During the glacial phase detailed carbon balance calculations show that CO2 levels in the atmosphere should stay the same or slightly rise, rather than falling from 280 ppm to 180 ppm. Higher solubility of CO2 in colder water is off-set by less water surface area and the contraction of the biosphere and biosphere's effectiveness to absorb CO2 during the glacial phase. The biosphere contracts as the planet is drier which converts vast areas of tropical forests to savana.

Puzzle 2
Missing CO2 sink in current times.

Puzzle 3
Evidence that in 19th and early 20th century that CO2 levels have fluctuated, with peaks as high as 400 ppm.

Puzzle 4
Explanation for rising and falling CO2 levels on geological time periods.

The four puzzles could be explained by a mechanism that modulates a carbon source to the planet's atmosphere. The upper ocean is currently saturated with CH4 which would indicate there is an input of CH4 into the ocean.

There is evidence that the biosphere constantly removes carbon from the atmosphere so there needs to be a steady input of carbon into the biosphere. One possible source (See Sloan Deep Carbon) is deep core carbon that is resident in the liquid core. As the liquid core solidifies the CH4 comes out of the liquid and moves up through the mantel.

So what is required is a mechanism that has increased the amount of CH4 that is released during the later half of the 20th century and that is cyclically suppressed during the glacial phase and then returns to the current normal during the interglacial phase.

The point is now one is looking for a changing CH4 input. To explain all observations.

Now assuming that the CO2 level increase in the 20th century was partly due to the increase in CH4 in the 20th century it then becomes possible for CO2 levels to fall if whatever has forcing the CH4 abates.

If that were the mechanism one should look at this time for a reduction in the rise of CO2 in the atmosphere. If there was a significant reduction in the rate of rise of CO2 or even falling CO2 levels that observation support a mechanism that has a modulated CH4 source.

 

[Xnn]

Saul;

Your link was to some type of denialist blog; not a reputable source.

Anyhow, concerning puzzle 1: I don't understand what the puzzle is. Please detail the calculations that you are referring to. If it's from a denialist; then consider that it's probably just a mis-representation of the science.

Puzzle 2: The Oceans are our current CO2 sink; why would anybody consider them missing? True, they are being over whelmed, but eventually thru increased precipitation and weathering, CO2 levels will stabilize. It's just going to take a 1000 years or so.

Puzzle 3: Really? Please show us.

Puzzle 4: Clearly there is more than 1 mechanism at work; and sorting them all out is a puzzling challenge. Besides the interplay between ocean temperatures and CO2 solubility, global precipitation and weathering, we have to consider Methane Clathrates,plate tectonics, volcanoes and implications of anoxic ocean conditions.

 

[mheslep]

The atomic testing produced C14 supports a retention time of around 4 years. ...

What is the molecular form of that C14 from atomic tests? Straight carbon particles (i.e. charcoal) or CO₂? It needs to be CO₂ to compare.

 

[Saul]

Saul;

Your link was to some type of denialist blog; not a reputable source.

Anyhow, concerning puzzle 1: I don't understand what the puzzle is. Please detail the calculations that you are referring to. If it's from a denialist; then consider that it's probably just a mis-representation of the science.

Puzzle 1
During the glacial phase detailed carbon balance calculations show that CO2 levels in the atmosphere should stay the same or slightly rise, rather than falling from 280 ppm to 180 ppm. Higher solubility of CO2 in colder water is off-set by less water surface area and the contraction of the biosphere and biosphere's effectiveness to absorb CO2 during the glacial phase. The biosphere contracts as the planet is drier which converts vast areas of tropical forests to savana.

The estimate of -8.5 ppm during the glacial phase is at the limit of the mechanisms. As noted in the paper an estimate of no change is also within the range of the carbon cycle mechanisms.

The hypothesis that the ocean pump is more efficient at removing CO2 begs the question how the ocean pump kept the CO2 levels low for 100 kyrs.

What is the time delay before CO2 rises after the planet warms?

http://www.seas.harvard.edu/climate/pdf/sigman-2000.pdf

Glacial/interglacial variations in atmospheric carbon dioxide

Twenty years ago, measurements on ice cores showed that the concentration of carbon dioxide in the atmosphere was lower during ice ages than it is today. As yet, there is no broadly accepted explanation for this difference. Current investigations focus on the ocean's `biological pump', the sequestration of carbon in the ocean interior by the rain of organic carbon out of the surface ocean, and its effect on the burial of calcium carbonate in marine sediments. Some researchers surmise that the whole-ocean reservoir of algal nutrients was larger during glacial times, strengthening the biological pump at low latitudes, where these nutrients are currently limiting. Others propose that the biological pump was more efficient during glacial times because of more complete utilization of nutrients at high latitudes, where much of the nutrient supply currently goes unused.

Table 1 Atmospheric CO2 effects of known changes Condition during the last ice age
(as different from Holocene) CO2 change (p.p.m.v.)
.......................
Terrestrial carbon decrease (500 Pg C) ---------------------(5)
Ocean cooling (58 low latitude, 2.58 high latitude)-------(-30)
Ocean salinity increase (3%)-----------------------------------( 6.5)
Total CO2 change-------------------------------------------------( -8.5)
.......................

 

[Saul]

This is an interesting graph.

Try to explain the shape of the graph assuming temperature is driving CO2 or CO2 is driving temperature.

Remember in the interglacial phase ice melting leads the CO2 rise by up to 1000 years.

http://www.jennifermarohasy.com/blog/archives/Siegenthaler,%20Nov%2005.html

http://www.realclimate.org/epica.jpg

 

[vanesch]

Try to explain the shape of the graph assuming temperature is driving CO2 or CO2 is driving temperature.

The point is that the situation now is maybe different, and the mechanism doesn't need to be the same. Even if in the past, it was temperature that was driving CO2, say, that doesn't mean that if you *add by hand* CO2, this is not having any influence.

Even if in the past, due to an other initial drive (say, solar), there was a temperature increase, and that was then the cause of a CO2 rise, this doesn't say anything about what happens when you influence directly the CO2 level.

In other words, the "input function" is different. Now we have good indications that the input function is human CO2 exhaust. If you look at a different input function into a complex system, the response is going to be different too.

This is why correlations, without a causal understanding, don't learn us much by themselves.

I might be wrong, but I think that there's something unique to the current situation, which is massive CO2 exhaust mostly independent of any other climate drive. I don't think that such a thing happened in the past in a similar situation. So there are no past data which describe exactly what we are living now. The only thing we can do is to try to *model* it and calculate.

We can use past data in order to *check* the general validity of the models. But we cannot predict what will happen now just based upon past data, because those past data don't contain anything similar to the current situation.

 

[Andre]

But those graphs are not depicting global temperature and concentration of CO2 in the atmosphere of the last several 100,000 years.

What they do show is isotope ratios and CO2 concetration of the ice in Antarctic ice cores and it is only an educated guess that these accurately represent climate of the past.

However with stunning corellations like that, one should be deeply suspicous, especially when other things in the explanations don't add up.