CO2: Ice Cores vs. Plant Stomata

Guest post by David Middleton

INTRODUCTION

Anyone who has spent any amount of time reviewing climate science literature has probably seen variations of the following chart…

A record of atmospheric CO2 over the last 1,000 years constructed from Antarctic ice cores and the modern instrumental data from the Mauna Loa Observatory suggest that the pre-industrial atmospheric CO2 concentration was a relatively stable ~275ppmv up until the mid 19th Century. Since then, CO2 levels have been climbing rapidly to levels that are often described as unprecedented in the last several hundred thousand to several million years.

Ice core CO2 data are great. Ice cores can yield continuous CO2 records from as far back as 800,000 years ago right on up to the 1970’s. The ice cores also form one of the pillars of Warmista Junk Science: A stable pre-industrial atmospheric CO2 level of ~275 ppmv. The Antarctic ice core-derived CO2 estimates are inconsistent with just about every other method of measuring pre-industrial CO2 levels.

Three common ways to estimate pre-industrial atmospheric CO2 concentrations (before instrumental records began in 1959) are:

1) Measuring CO2 content in air bubbles trapped in ice cores.

2) Measuring the density of stomata in plants.

3) GEOCARB (Berner et al., 1991, 1999, 2004): A geological model for the evolution of atmospheric CO2 over the Phanerozoic Eon. This model is derived from “geological, geochemical, biological, and climatological data.” The main drivers being tectonic activity, organic matter burial and continental rock weathering.

ICE CORES

The advantage of Antarctic ice cores is that they can provide a continuous record of relative CO2 changes going back in time 800,000 years, with a resolution ranging from annual in the shallow section to multi-decadal in the deeper section. Pleistocene-age ice core records seem to indicate a strong correlation between CO2 and temperature; although the delta-CO2 lags behind the delta-T by an average of 800 years…

Ice cores from Greenland are rarely used in CO2 reconstructions.  The maximum usable Greenland record only dates as far back as ~130,000 years ago (Eemian/Sangamonian); the deeper ice has been deformed.  The Greenland ice cores do tend to have a higher resolution than the Antarctic cores because there is a higher snow accumulation rate in Greenland.  Funny thing about the Greenland cores: They show much higher CO2 levels (330-350 ppmv) during Holocene warm periods and Pleistocene interstadials.  The Dye 3 ice core shows an average CO2 level of 331 ppmv (+/-17) during the Preboreal Oscillation (~11,500 years ago).  These higher CO2 levels have been explained away as being the result of in situ chemical reactions (Anklin et al., 1997).

PLANT STOMATA

Stomata are microscopic pores found in leaves and the stem epidermis of plants. They are used for gas exchange. The stomatal density in some C3 plants will vary inversely with the concentration of atmospheric CO2. Stomatal density can be empirically tested and calibrated to CO2 changes over the last 60 years in living plants. The advantage to the stomatal data is that the relationship of the Stomatal Index and atmospheric CO2 can be empirically demonstrated…

Wagner et al., 2004. Reproducibility of Holocene atmospheric CO2 records based on stomatal frequency. Quaternary Science Reviews 23 (2004) 1947–1954.

When stomata-derived CO2 (red) is compared to ice core-derived CO2 (blue), the stomata generally show much more variability in the atmospheric CO2 level and often show levels much higher than the ice cores…

Plant stomata suggest that the pre-industrial CO2 levels were commonly in the 360 to 390ppmv range.

GEOCARB

GEOCARB provides a continuous long-term record of atmospheric CO2 changes; but it is a very low-frequency record…

The lack of a long-term correlation between CO2 and temperature is very apparent when GEOCARB is compared to Veizer’s d18O-derived Phanerozoic temperature reconstruction. As can be seen in the figure above, plant stomata indicate a much greater range of CO2 variability; but are in general agreement with the lower frequency GEOCARB model.

DISCUSSION

Ice cores and GEOCARB provide continuous long-term records; while plant stomata records are discontinuous and limited to fossil stomata that can be accurately aged and calibrated to extant plant taxa. GEOCARB yields a very low frequency record, ice cores have better resolution and stomata can yield very high frequency data. Modern CO2 levels are unspectacular according to GEOCARB, unprecedented according to the ice cores and not anomalous according to plant stomata. So which method provides the most accurate reconstruction of past atmospheric CO2?

The problems with the ice core data are 1) the air-age vs. ice-age delta and 2) the effects of burial depth on gas concentrations.

The age of the layers of ice can be fairly easily and accurately determined. The age of the air trapped in the ice is not so easily or accurately determined. Currently the most common method for aging the air is through the use of “firn densification models” (FDM). Firn is more dense than snow; but less dense than ice. As the layers of snow and ice are buried, they are compressed into firn and then ice. The depth at which the pore space in the firn closes off and traps gas can vary greatly… So the delta between the age of the ice and the ago of the air can vary from as little as 30 years to more than 2,000 years.

The EPICA C core has a delta of over 2,000 years. The pores don’t close off until a depth of 99 m, where the ice is 2,424 years old. According to the firn densification model, last year’s air is trapped at that depth in ice that was deposited over 2,000 years ago.

I have a lot of doubts about the accuracy of the FDM method. I somehow doubt that the air at a depth of 99 meters is last year’s air. Gas doesn’t tend to migrate downward through sediment… Being less dense than rock and water, it migrates upward. That’s why oil and gas are almost always a lot older than the rock formations in which they are trapped. I do realize that the contemporaneous atmosphere will permeate down into the ice… But it seems to me that at depth, there would be a mixture of air permeating downward, in situ air, and older air that had migrated upward before the ice fully “lithified”.

A recent study (Van Hoof et al., 2005) demonstrated that the ice core CO2 data essentially represent a low-frequency, century to multi-century moving average of past atmospheric CO2 levels.

Van Hoof et al., 2005. Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis. Tellus (2005), 57B, 351–355.

It appears that the ice core data represent a long-term, low-frequency moving average of the atmospheric CO2 concentration; while the stomata yield a high frequency component.

The stomata data routinely show that atmospheric CO2 levels were higher than the ice cores do. Plant stomata data from the previous interglacial (Eemian/Sangamonian) were higher than the ice cores indicate…

Rundgren et al., 2005. Last interglacial atmospheric CO2 changes from stomatal index data and their relation to climate variations. Global and Planetary Change 49 (2005) 47–62.

The GEOCARB data also suggest that ice core CO2 data are too low…

The average CO2 level of the Pleistocene ice cores is 36ppmv less than GEOCARB…

Recent satellite data (NASA AIRS) show that atmospheric CO2 levels in the polar regions are significantly less than in lower latitudes…

"AIRS can observe the concentration of carbon dioxide in the mid-troposphere, with 15,000 daily observations, pole to pole, all over the globe, with an accuracy of 1 to 2 parts per million and a horizontal surface resolution of 1 by 1 degree. The monthly map at right allows researchers to better observe variations of carbon dioxide at different latitudes and during different seasons. Image credit: NASA" http://www.nasa.gov/topics/earth/agu/airs-images20091214.html

"AIRS data show that carbon dioxide is not well mixed in Earth's atmosphere, results that have been validated by direct measurements. The belt of carbon dioxide concentration in the southern hemisphere, depicted in red, reaches maximum strength in July-August and minimum strength in December-January. There is a net transfer of carbon dioxide from the northern hemisphere to the southern hemisphere. The northern hemisphere produces three to four times more human produced carbon dioxide than the southern hemisphere. Image credit: NASA" http://www.nasa.gov/topics/earth/agu/airs-images20091214.html

So… The ice core data should be yielding lower CO2 levels than the Mauna Loa Observatory and the plant stomata.

Kouwenberg et al., 2005 found that a “stomatal frequency record based on buried Tsuga heterophylla needles reveals significant centennial-scale atmospheric CO2 fluctuations during the last millennium.”

Plant stomata data show much greater variability of atmospheric CO2 over the last 1,000 years than the ice cores and that CO2 levels have often been between 300 and 340ppmv over the last millennium, including a 120ppmv rise from the late 12th Century through the mid 14th Century. The stomata data also indicate higher CO2 levels than the Mauna Loa instrumental record; but a 5-point moving average ties into the instrumental record quite nicely…

A survey of historical chemical analyses (Beck, 2007) shows even more variability in atmospheric CO2 levels than the plant stomata data since 1800…

WHAT DOES IT ALL MEAN?

The current “paradigm” says that atmospheric CO2 has risen from ~275ppmv to 388ppmv since the mid-1800’s as the result of fossil fuel combustion by humans. Increasing CO2 levels are supposedly warming the planet…

However, if we use Moberg’s (2005) non-Hockey Stick reconstruction, the correlation between CO2 and temperature changes a bit…

Moberg did a far better job in honoring the low frequency components of the climate signal. Reconstructions like these indicate a far more variable climate over the last 2,000 years than the “Hockey Sticks” do. Moberg also shows that the warm up from the Little Ice Age began in 1600, 260 years before CO2 levels started to rise.

As can be seen below, geologically consistent reconstructions like Moberg and Esper are in far better agreement with “direct” paleotemperature measurements, like Alley’s ice core reconstruction for Central Greenland…

In fairness to Dr. Mann, his 2008 reconstruction did restore the Medieval Warm Period and Little Ice Age to their proper places; but he still used Mike’s Nature Trick to slap a hockey stick blade onto the 20th century.

What happens if we use the plant stomata-derived CO2 instead of the ice core data?

We find that the ~250-year lag time is consistent. CO2 levels peaked 250 years after the Medieval Warm Period peaked and the Little Ice Age cooling began and CO2 bottomed out 240 years after the trough of the Little Ice Age. In a fashion similar to the glacial/interglacial lags in the ice cores, the plant stomata data indicate that CO2 has lagged behind temperature changes by about 250 years over the last millennium. The rise in CO2 that began in 1860 is most likely the result of warming oceans degassing.

While we don’t have a continuous stomata record over the Holocene, it does appear that a lag time was also present in the early Holocene…

Once dissolved in the deep-ocean, the residence time for carbon atoms can be more than 500 years. So, a 150- to 200-year lag time between the ~1,500-year climate cycle and oceanic CO2 degassing should come as little surprise.

CONCLUSIONS

  • Ice core data provide a low-frequency estimate of atmospheric CO2 variations of the glacial/interglacial cycles of the Pleistocene. However, the ice cores seriously underestimate the variability of interglacial CO2 levels.
  • GEOCARB shows that ice cores underestimate the long-term average Pleistocene CO2 level by 36ppmv.
  • Modern satellite data show that atmospheric CO2 levels in Antarctica are 20 to 30ppmv less than lower latitudes.
  • Plant stomata data show that ice cores do not resolve past decadal and century scale CO2 variations that were of comparable amplitude and frequency to the rise since 1860.

Thus it is concluded that:

  • CO2 levels from the Early Holocene through pre-industrial times were highly variable and not stable as the Antarctic ice cores suggest.
  • The carbon and climate cycles are coupled in a consistent manner from the Early Holocene to the present day.
  • The carbon cycle lags behind the climate cycle and thus does not drive the climate cycle.
  • The lag time is consistent with the hypothesis of a temperature-driven carbon cycle.
  • The anthropogenic contribution to the carbon cycle since 1860 is minimal and inconsequential.

 

Note: Unless otherwise indicated, all of the climate reconstructions used in this article are for the Northern Hemisphere.

References

Anklin, M., J. Schwander, B. Stauffer, J. Tschumi, A. Fuchs, J.M. Barnola, and D. Raynaud, CO2 record between 40 and 8 kyr BP from the GRIP ice core, Journal of Geophysical Research, 102 (C12), 26539-26545, 1997.

Wagner et al., 1999. Century-Scale Shifts in Early Holocene Atmospheric CO2 Concentration. Science 18 June 1999: Vol. 284. no. 5422, pp. 1971 – 1973.

Berner et al., 2001. GEOCARB III: A REVISED MODEL OF ATMOSPHERIC CO2 OVER PHANEROZOIC TIME. American Journal of Science, Vol. 301, February, 2001, P. 182–204.

Kouwenberg, 2004. APPLICATION OF CONIFER NEEDLES IN THE RECONSTRUCTION OF HOLOCENE CO2 LEVELS. PhD Thesis. Laboratory of Palaeobotany and Palynology, University of Utrecht.

Wagner et al., 2004. Reproducibility of Holocene atmospheric CO2 records based on stomatal frequency. Quaternary Science Reviews 23 (2004) 1947–1954.

Esper et al., 2005. Climate: past ranges and future changes. Quaternary Science Reviews 24 (2005) 2164–2166.

Kouwenberg et al., 2005. Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles. GEOLOGY, January 2005.

Van Hoof et al., 2005. Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis. Tellus (2005), 57B, 351–355.

Rundgren et al., 2005. Last interglacial atmospheric CO2 changes from stomatal index data and their relation to climate variations. Global and Planetary Change 49 (2005) 47–62.

Jessen et al., 2005. Abrupt climatic changes and an unstable transition into a late Holocene Thermal Decline: a multiproxy lacustrine record from southern Sweden. J. Quaternary Sci., Vol. 20(4) 349–362 (2005).

Beck, 2007. 180 Years of Atmospheric CO2 Gas Analysis by Chemical Methods. ENERGY & ENVIRONMENT. VOLUME 18 No. 2 2007.

Loulergue et al., 2007. New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr. Clim. Past, 3, 527–540, 2007.

DATA SOURCES

CO2

Etheridge et al., 1998. Historical CO2 record derived from a spline fit (75 year cutoff) of the Law Dome DSS, DE08, and DE08-2 ice cores.

NOAA-ESRL / Keeling.

Berner, R.A. and Z. Kothavala, 2001. GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2002-051. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Kouwenberg et al., 2005. Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles. GEOLOGY, January 2005.

Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. 2008. High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382, 15 May 2008. doi:10.1038/nature06949.

Royer, D.L. 2006. CO2-forced climate thresholds during the Phanerozoic. Geochimica et Cosmochimica Acta, Vol. 70, pp. 5665-5675. doi:10.1016/j.gca.2005.11.031.

TEMPERATURE RECONSTRUCTIONS

Moberg, A., et al. 2005. 2,000-Year Northern Hemisphere Temperature Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2005-019. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Esper, J., et al., 2003, Northern Hemisphere Extratropical Temperature Reconstruction, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2003-036. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Mann, M.E. and P.D. Jones, 2003, 2,000 Year Hemispheric Multi-proxy Temperature Reconstructions, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2003-051. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Alley, R.B.. 2004. GISP2 Ice Core Temperature and Accumulation Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-013. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

VEIZER d18O% ISOTOPE DATA. 2004 Update.

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latitude

“The rise in CO2 that began in 1860 is most likely the result of warming oceans degassing.”
=============================================
Just like it has always been………………..

tommoriarty

David,
thank you for the very interesting post. Could you please modify the images to have links to individual pages? I find that the graphs extend out into the right sidebar and are partially covered by the items in the sidebar. For example, I cannot read the caption on the Wagner et. al. image because it is partially covered by the right sidebar.
Links that open the images in their own pages would solve this minor problem and would be greatly appreciated.
Best regards,
Tom Moriarty
ClimateSanity.wordpress.com

Pamela Gray

Very nice post. Well thought out. Follows standard research article format. Leaves out emotional baggage on either side. Develops summaries based on the data alone. Written at a level and without jargon, that most can readily understand. Would have been nice to see what further information/data analysis would be useful to investigate.

Pamela Gray

Might we be able to reconstruct the greening of the planet during these episodes of stomata changes? I am guessing there is a correlate lag similar to CO2 reconstruction. Fossil remnants would be useful to measure this, especially around the supposed edges of such “greening”.

JT

Welcome survey of all to often neglected evidence. A good companion to this post would be Jeffrey Glassman’s paper showing the consistency of the vostok record with Henry’s Law:
http://rocketscientistsjournal.com/2006/10/co2_acquittal.html#more

Baa Humbug

Interesting and informative and obviously took some time and effort to put together.
Thankyou.

John Cunningham

A fascinating post, indeed. I have been searching the net, and have not found an answer to this question–are there instruments currently measuring CO2 anywhere other than Mauna Loa? although it is apparently widely assumed that atmospheric concentrations are homogeneous worldwide, it would be useful to know if there is a second site to provide a backup to Mauna Loa.
[Yes; from c. 100 other sites wordwide. The CO2 data itself does not seem to be the problem. Rather, the effect of CO2 seems to be the issue. ~ Evan]

Keith W.

Nice breakdown. I’ve been questioning the ice core data for a while. You do have to marvel at how the major core reference used by the Alarmist side is usually Lonnie Thompson’s, but no one can find his actual data to confirm his work. Makes getting Phil Jones’ homework look simple.

John S

If a layman may ask a stupid question:
Why does the Mauna Loa CO2 readings go up in such a perfectly straight line, in spite of year over year variations in fossil fuel usage, widespread deforestation, and whatever other factors contribute to the amount of CO2 in the Atmosphere.
It just seems that the CO2 levels year over year wouldn’t be such a nice straight line for so many years.

Bill Illis

Good post David.
Just one comment: The stomata-based CO2 estimates seem to be generally accurate, but they do exhibit a lot of varibility which means there is a large error margin in the methodology for individual estimates. They should probably be averaged over some longer time period.

INGSOC

Pamela Gray says:
December 26, 2010 at 9:04 am
Might we be able to reconstruct the greening of the planet during these episodes of stomata changes? I am guessing there is a correlate lag similar to CO2 reconstruction. Fossil remnants would be useful to measure this, especially around the supposed edges of such “greening”.
I too have wondered aloud as to this question. I would imagine that someone has at some point thought of coming at the CO2 conundrum from the other direction; if not to show causation then then for little more than curiosity?

Great analysis, many thanks for this.

Warren in Minnesota

The article was most interesting. However, I find the two directions of time on the x-axes presented in the graphs to be confusing or difficult to compare. In some cases, time to the present goes to the left, and in the other cases, time to the present goes to the right. Most of the contemporary charts such as the little ice ages or the hockey stick have the present ending on the right. But the ice core graphs have the present starting on the left.

H.R.

Excellent post, David. I’ve read about the 3 methods individually but this is the first time I’ve seen all three discussed together. Very easy to read and understand. Thank you.

Tim McHenry

“The age of the layers of ice can be fairly easily and accurately determined”
I challenge this. They still cannot explain how things that they think should be hundreds if not thousands of years old in Greenland can be buried as deep as they are from past settlements and even airplanes! If there is an explanation of this then give me the link.

Steve Koch

Wow! So thorough, so methodical, very impressive. You should publish it in a peer reviewed publication.

richard telford

Stomata-based estimates of CO2 concentration are far from infallible. Indeed, for some species, there is little or no correlation between stomatal density and CO2 concentration.
See Eide & Birks 2004 Stomatal frequency of Betula pubescens and Pinus sylvestris shows no proportional relationship with atmospheric CO2 concentration http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2004.tb00848.x/abstract

D. King

Pamela Gray says:
December 26, 2010 at 8:58 am
Written at a level and without jargon, that most can readily understand.
Yes, very well done.
Thanks David.

Doug in Seattle

David:
Great review of the three methods of paleo CO2 determinations.
Looks like C3 stomata provides a good method for high resolution CO2 measurements. Pity that the spatial and temporal resolution is so spotty. Clearly more work needs to be done, and I hope that those doing the research are not being hobbled by the funding bosses due to the inconvenient results.

noaaprogrammer

Excellent post David. Have there been any studies done on refining models for the upward and downward diffusion of gasses in ice pores, using nuclear tagging provided by above-ground nuclear testing during the 1950s?

Just precisely why do you exaggerate the behavior of CO2 in the first figure by leaving out the bottom of the scale? The true shape of the curve can only be seen if you start the vertical scale from zero instead of from 230. These tricks should not be employed if you want to be objective in your presentation.

Economic Geologist

From one geoscientist to another: nice piece of work.
Thanks for putting this together.

Slabadang

Great article!
Very educational and well structured. I cant find out whether the CO2 measurements from Mauna Loa takes into account that the CO2 levels are lower at the poles than over lower latitudes. Otherwise they are comparing apples and oranges in thier statistics.

@ tommoriarty: If you will right click on the image, you may select view image or open image. That works in Firefox, Opera and Chrome/Safari. I have no clue how to do it in IE.
cheers,
gary

Engchamp

David,
Thank you for your excellent, well presented post.
I have rarely learnt so much in an hour or so than by reading it, although I have to admit my ignorance of a few items.
If I may make so bold, I have arrived at the following…
Temperature in the oceans varies in different areas, hence dissolved CO2 in sea water varies in different oceans;
atmospheric concentrations of CO2 vary geographically;
different methods of measuring past CO2 levels (ice cores & plant stomata) can result in huge variations – >50% at times, although GEOCARB may provide a ‘steadier’ historical record;
there are difficulties in measuring the age of air:ice, and the effects of gas compression at depth;
temperature variation precedes CO2 level variation, upwards or downwards.
Aside from the last point, if I am correct in assuming the others are true, then it would appear that yet more complication is prevalent.
Speaking for myself, the more one delves deeper into any particular aspect of climate, the more one realises how little is known of the whole.

Dave Springer

@Middleton
The amount of anthropogenic CO2 released into the atmosphere is one of the better known quantities in this debate. The directly measured increase in atmospheric CO2 if only about half of the anthropogenic emissions. Clearly something is sequestering about half the anthropogenic CO2 emissions. For you to say that the increase is the result of ocean outgassing instead of anthropogenic emission frankly makes very little sense. Environmental sinks do not discriminate between CO2 molecules by source. It almost seems writ in granite that the oceans are not currently a source of CO2 but are rather a sink of CO2 and they aren’t sinking it as fast as anthropoids are sourcing it.
There are a few things in the global warming controversy which are almost beyond reasoned debate. The measured rise in CO2 being due to human activities is one of those few things.

What a goldmine of relevant information!! The author did a lot of work compiling these data, perfect, thanks 🙂
K.R. Frank

R. Gates

Thanks for the very informative post. The general point– that CO2 may have had more variability than ice cores data can show is a valid one, but one should use caution when talking about the accuracy of stomatal densities as their response to CO2 can be quite variable and nolinear and may also be related to other factors such as humidity and temperatures. This is a new area of research with even the lead researchers acknowledging the uncertainties of the science. I am fairly certain however that CO2 was more varible in the past than assumed by the IPCC but the fidelity of the ice core measurements would not yeild such data, however, the longer term TRENDS of atmospheric CO2 over the past 800,000 years as displayed is the ice cores is very likely correct. As stated, stomatal density as a proxy for past CO2 levels is still a relatively young science with known issues and problems that are well documented and caution is warranted before making large assumptions based this new field.
A few conclusions that are probably safe to make, drawn from studies such as this:
http://www.pnas.org/content/early/2008/10/03/0807624105.full.pdf
“A coherent scenario explaining preindustrial atmospheric CO2
changes of the last millennium and their possible temporal link
with changes in terrestrial and marine carbon uptake or release
still needs to be established. Reconstructed multidecadal
changes are not as prominent as man-made CO2 increases since
the onset of industrialization. Yet it seems obvious that a
dynamic CO2 regime with fluctuations of up to 34 ppmv implies
that CO2 can no longer be discarded as a forcing factor of
preindustrial air-temperature changes. The results of our study
therefore underscore the need to understand anthropogenic
global warming within the context of rates and amplitudes of
natural CO2 variability of the last millennium. A stomata-based
CO2 record may provide an important observational constraint
on the sensitivity of climate models.”

Pamela Gray

Would that Mann had been so cautious about tree rings, a well known caveat had he bothered with it.

JDN

@David: I’ll consider this a late X-mas present. Are you planning on taking this report forward to a scientific journal?

As the Mauna Loa data shows there is little variation from year to year [apart from the general rise], so any other method that seems to show very large variations must have a much larger noise level, and most of the variation would then be the just noise. A standard way of beating down the noise is to average over enough time. Such a long-term average would include any systematic errors there might be.

Pamela Gray

Dave, the natural closed systems (such as human population growth as a direct contributor to the recent rise in CO2) have well known closed system lags and unbalances. This is well established in proxies such as ice cores and stomata data mined for CO2 data. The current rise might very well be due to a closed system on the rising side of the closed equation that includes a lag time in response. It may also be due to a faster out of control rise on one side of the closed equation with a slower catching up on the downside of a closed equation. No where is it scientifically stated that a closed system is always instantaneously balanced. Nature is necessarily unbalanced and is always under pressure to change, which is likely what makes it so robust.
Logically, eventually as the human animal population increases as it is currently doing in dramatic fashion, the ability to sustain such a growth will crumble. Left unchecked, we are breeding a future population of increasing starvation and eventual population deflation. But that is the nature of closed systems. We are no different than a bloom of locusts if viewed from such a lens.
In my opinion, your view of CO2 cycles and data is myopically biased by emotional belief.

Dave Springer

Doug in Seattle says:
December 26, 2010 at 10:17 am
“Looks like C3 stomata provides a good method for high resolution CO2 measurements.”
Stomata density is determined by many factors other than CO2. The amount of light the plant receives, temperature, water stress, and nutrients among them.
Using stomata count as a proxy for CO2 is about as reliable as using tree ring width for determining temperature. We all know how well that proxy worked out (cough cough hide the decline cough cough).
Moreover stomata density isn’t even consistent on the leaves of the same plant. Mature leaves produce signalling proteins in response to environmental factors and the level of these signalling proteins control the stomata density on developing leaves so that the new leaves are optimized for the conditions the mature leaves are experiencing. So, for instance, a string of cloudy days experienced by mature leaves changes the stomata density on newly forming leaves.
A year or a decade with a lot of clouds (with no change in CO2) will effect stomata density. Similarly dry and wet years will change stomata density. More or less competition for CO2 from other plants will also change stomata density. Exceptionally good or bad conditions for one kind of plant will leave more less CO2 for other plants. Same goes for producers of CO2 such as fungi. A great year for fungi growth will temporarily raise the CO2 level near the ground and a poor year will lower it. Near surface CO2 concentration is highly variable.

Dave Springer

@Pamela
“In my opinion, your view of CO2 cycles and data is myopically biased by emotional belief.”
I’m about as emotionally biased as an eggplant. You’re projecting.

John F. Hultquist

Warren,
When diagrams are used from previous reports (note the plurals) they are usually used as originally constructed; maybe with something new added. To reverse them side-to-side (mirror) or top-to-bottom (flip) requires (a) the original data, or (b) tedious measurements from the original, and considerable graphics capability –any of which can lead to mistakes, and problems going back to the original source text of clarification.
Try doing such a thing. Take the Pleistocene CO2 vs Temperature chart with four lines (one straight orange one) and five balloon style text boxes and (mirror) it so the x-axis has 0 on the right and 1 on the left. This is easy in a graphics program but the letters and numbers in the chart and in the caption will have to be recreated. And, then as mentioned, the original referenced text (perhaps) will be scrambled.
———————————————————
David, Nice post. Thanks.
Good comments, also. Thanks to you folks.

1DandyTroll

If they were true scientist they’d not use two different localized reading to compare against each other and call the result global.
Mauna loa can only be compared to mauna loa. And so where are the 1000 years of readings from that location? (Heh, it’d be pretty freakish if they did have those readings though.)
If I understood it correct they only spliced together the Mauna loa because the ice core readings is non existent the closer to present we get. Boo hoo, but when ever have it essentially been correct to splice together data from two, or more, different locations showing local conditions only into one show and not get a freak show?

Dave Springer

@Pamela
“Logically, eventually as the human animal population increases as it is currently doing in dramatic fashion, the ability to sustain such a growth will crumble. Left unchecked, we are breeding a future population of increasing starvation and eventual population deflation.”
Paul Erlichism appears to rise and fall in correlation with dress hem length. In the meantime technological advances continue to outpace population growth. Average life expectancy continues to increase even as the number of individuals living those lives increases. Make a logical case for why technological advance cannot continue to outpace population growth and I’ll consider the merits of it. Good luck.

Pretty darned nice post. It took a lot of work to assemble all of this. Very much appreciated.

anna v

One should be reminded that there is a fourth method of measuring CO2, as was discussed here the compilation of the late Ernst-Georg Beck of the 200 year record of chemical measurements. These also show large variations of CO2.
The way I have been looking at these discrepancies is not in terms of noise, but in terms of geographical and height variations, as happens also with temperature. In contrast to the method of getting a global average from the surface temperatures, the CO2 is measured at high and remote places, and with an orthodox method of analysis outlined by all the Keeling et al publications.
Ice cores are far away from biological sources. Stomata by construction are not, and will reflect values similar to the values seen in the Beck compilations.
Mauna Loa measure next to a volcano, and volcanoes are known sources of CO2. They have a funny way of throwing away outliers in the analysis. All these were discussed previously.
As one does not go to the top of a mountain and measure the temperature and call it the global temperature one should not declare the Mauna Loa values as global either.

Joel Shore

Modern satellite data show that atmospheric CO2 levels in Antarctica are 20 to 30ppmv less than lower latitudes.

Where do you get this from? This image http://www.nasa.gov/images/content/411791main_slide5-AIRS-full.jpg suggests the entire variation over the earth is around 7ppm. The difference between the average value in the lower latitudes and the high latitudes is even less. The variability would also be expected to be greater at a time like the present when CO2 levels are increasing rapidly than at times when CO2 levels were not rapidly changing.

GEOCARB shows that ice cores underestimate the long-term average Pleistocene CO2 level by 36ppmv.

So, in other words, models are garbage and should not be believed over data except when they tell us what we want to believe. It is in fact worse than this because you are using the GEOCARB model in a way that my guess is even the creators of that model would say is trusting it beyond its capabilities. So, basically, what you are probably doing is believing models over data in a regime when the modelers know that the model cannot be trusted to this degree of accuracy!

Plant stomata data show that ice cores do not resolve past decadal and century scale CO2 variations that were of comparable amplitude and frequency to the rise since 1860.

And, you choose to believe these noisy data because…Oh yeah, they tell you what you want to believe even though there is no good explanation of what could possibly cause such rapid variations in CO2 levels in the past.

DEL

Excellent presentation!
As we know CO2 is a good thing; the more their is, the more life on the planet and the inverse. As I understand, at about 150ppm terrestrial plant growth stops, and being the basis of the food chain, would be a big problem.
We know that atmospheric CO2 has been in the long term decline. The Phanerozoic CO2 vs Temp chart clearly shows the slow long term decline over the last ~530MY. Extending the trend line of the peaks shows, that unless the system will naturally bounce off the 150ppm point, it may break through in the next few MYs (1-10?). Not that it is a personal worry and our species may be long gone anyway.
However, as has been shown here and in multiple presentations, as temp goes down, CO2 follows 230-800 years later.
Of more pressing concern should be the unavoidable imminent climate shift back to the normal state of full-on glacial advance and the following large CO2 and food production decline. I just fail to understand why that is not the big debate; how will civilization survive in any recognizable form when the planet quickly shifts from a carrying capacity of 8 Bil people to 2 Bil people and large regions must be abandoned; such as the UK, Northern Europe, Canada, New York, Chicago….? What is the plan? This should be the focus of even marginally responsible governments. It probably secretly is, but since time is running short, and once the shift is clearly underway, too late; it needs to be made public; what the hard decisions will be. Ultimately people are responsible for themselves, but how the future population will best fit and work together should not be left as a State secret. I probably won’t live to see it, but our decedents, at some point, will.

tjfolkerts

GEOCARB is a computer model where the input data is averages in 10 million year chunks.
Why then do you conclude “GEOCARB shows that ice cores underestimate the long-term average Pleistocene CO2 level by 36ppmv.”
1) The time scales are different.
2) You are accepting an average from a computer model with large uncertainty over actual measurements of CO2 levels. That’s like saying “computer models show a warming of 1 C the last century, but actual thermometers only show an increase of 0.5 C. Thus we conclude that the thermometers are too low by 0.5 C.”
* Plant stomata estimates of CO2 fall by over 100 ppm in a few decades from ~1530 – 1560 AD.
* Beck’s estimates of CO2 rise AND fall by over 100 ppm in a few decades from ~ 1925 – 1955 AD.
Do your truly think that the concentrations changed that dramatically over such a short time, and if so, what might have caused this change? If you don’t believe the concentration changed so dramatically, then why would you believe these data are in any way more reliable than ice cores?
The abstract for the article you site (Anklin et al., 1997) says “to the early Holocene with concentrations between 290 and 310 ppmv”. This seems to contradict your claim of “CO2 levels (330-350 ppmv) during Holocene warm periods”

phlogiston

Excellent and extremely useful synthesis and summary of this topic David, many thanks. The figure on Phanerozoic temperature (Veizer) against CO2 by stomata and GEOCARB is hugely significant – in a way a mutual validation of stomata and GEOCARB.
One small comment – figure numbers would be helpful.
The conclusions are solidly grounded and hard-hitting.

harrywr2

Pamela Gray says:
December 26, 2010 at 11:19 am
“Logically, eventually as the human animal population increases as it is currently doing in dramatic fashion, the ability to sustain such a growth will crumble.”
Pamela, you really need to take a look at the actual population numbers.
The death rate is whats driving population numbers.
Every year the replacement for 1.1% of us is born. Only 0.8% of us depart.
Not to worry, effective January 1st medicare will pay doctors to inform the elderly of their patriotic duty to forgo medical care end of life options annually.

Joel Shore

DEL says:

Of more pressing concern should be the unavoidable imminent climate shift back to the normal state of full-on glacial advance and the following large CO2 and food production decline. I just fail to understand why that is not the big debate; how will civilization survive in any recognizable form when the planet quickly shifts from a carrying capacity of 8 Bil people to 2 Bil people and large regions must be abandoned; such as the UK, Northern Europe, Canada, New York, Chicago….?

I have one word for you: TIMESCALES. The rate of warming out of the glacial periods was on the order of 0.1 C per century and the descent into the glacial periods was even slower. So, even if the human emissions of CO2 weren’t already enough to at least delay the next glacial period, we would have plenty of time to get ready for it.
The temperature record does show some more rapid changes occurring but these were probably more regional in nature (i.e., some regions warming, some cooling, some not changing much) and seemed to occur during the glacial periods or during the periods when the climate was already changing rapidly. At best they are irrelevant for current considerations and at worst they warn us that one applies forcings to a very complex and nonlinear climate system at one’s peril!

Pamela Gray

Technology improvements take money and food in your belly. Something 3rd world net-food importation countries don’t have a lot of. What they do have are dwindling sources of food compared to their population growth.
Food production per capita hides the actual observations. As does food consumption per capita. While low birth-rate countries are consuming more food, high-birth rate countries are consuming less.
I am betting most warmers have a simplistic view of food production, food consumption, and population growth, much like the over-reliance on a global temperature average. These kinds of averages exchange valuable information for sound bites.

David, there are far more severe problems with the stomata data and the historical measurements (pre-Mauna Loa) than with the ice core data.
The main problem is that stomata by definition are from leaves of growing vegetation on land. That means that the local CO2 levels are highly variable from day to day (and night) and year by year. Even if the stomata (index) data are calibrated (+/- 10 ppmv) against ice cores (!) over the past century, there is not the slightest reason to expect that the same calibration is valid over previous centuries: Take e.g. one of the main datasets of The Netherlands: St. Odiliënberg, South Netherlands: in todays main wind direction a lot of industry and trafic of one of the densiest populations of the world. In the previous centuries: a lot of changes from woods and marshes to agriculture and industry/traffic. Even the main wind direction (and CO2 levels) might have changed from the MWP over the LIA to today.
The same problem for a lot of the late Beck’s historical data: taken at places where there were a lot of local CO2 sources and sinks. E.g. the 1942 peak in his reconstruction is mainly based on two places: Poona (India), most measurements within crops, and Giessen (Germany), where modern measurements show a huge bias and extreme much variability. BTW, the 1942 “peak” doesn’t show up in stomata (index) data, neither in high resolution ice cores or (as d13C) in coralline sponges (2-4 years resolution).
Here the modern data from Giessen, compared to the same days measured (raw data!) at Mauna Loa, Barrow and the South Pole:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/giessen_background.jpg
Do you think that historical data from Giessen (3 samples/day taken at 7 AM, 2 and 9 PM, that alone gives a bias of +40 ppmv) have any value for historical background CO2 levels?
Further, the ice cores CO2 measurements of Greenland are unreliable, because of the frequent acid dust from Icelandic volcanoes deposited on the ice. Together with seadust carbonate deposits that gives extra CO2.
Ice core problems like the ice age – gas age difference are difficult to resolve, but have no influence on CO2 levels at all. But there is an averaging over several (10-600) years of the gas composition during narrowing of the pores with depth. Thus at bubble closing time the gas composition is not of today, but a mix of some to many years.
The oceans are NOT the cause of rising CO2: the direct solubility of CO2 in seawater changes with about 16 ppmv/°C, by far not enough to explain the 100 ppmv rise since 1850 or even the 60 ppmv rise since 1958. Because of the negative feedback from vegetation, the real response of CO2 on temperature is about 8 ppmv/°C (ice ages – interglacials, MWP-LIA) on long term, some 4 ppmv/°C for short term variations around the trend.
And the geocarb is based on proxies, while the inclusion of air in ice cores allows a direct measurement, thus is not a proxy, quite accurate, but smoothed, if handled with care.
See further my take on the CO2 increase at:
http://wattsupwiththat.com/2010/08/05/why-the-co2-increase-is-man-made-part-1/ about the mass balance of man-made CO2 emissions and the increase in the atmosphere.
http://wattsupwiththat.com/2010/08/20/engelbeen-on-why-he-thinks-the-co2-increase-is-man-made-part-2/ about the reliability of ice cores.
http://wattsupwiththat.com/2010/09/16/engelbeen-on-why-he-thinks-the-co2-increase-is-man-made-part-3/ about additional evidence from isotope compositions.
http://wattsupwiththat.com/2010/09/24/engelbeen-on-why-he-thinks-the-co2-increase-is-man-made-part-4/ about where one finds “background” CO2 and further discussion of Beck’s historical data and stomata data.

1DandyTroll says:
December 26, 2010 at 11:42 am
If they were true scientist they’d not use two different localized reading to compare against each other and call the result global.
CO2 levels are measured in “background” conditions at some 70+ places over the world + satellites. “Background” levels are within 5 ppmv for 95% of the atmosphere, from near the North Pole to the South pole for yearly averages, but +/- 10 ppmv for seasonal changes. See:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/co2_trends.jpg
If I understood it correct they only spliced together the Mauna loa because the ice core readings is non existent the closer to present we get.
Depends of the accumulation rate: the high snowfall near the seaside allows that the ice already closes after few decades at 72 meter depth (Law Dome, 1.5 meter ice equivalent per year), but the drawback is that it doesn’t go back more than 150 years. For Dome C that takes millennia (only a few mm snow per year), but we can read back some 800,000 years.
For Law Dome, there is an overlap of some 20 years with the direct measurements at the South Pole:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/law_dome_sp_co2.jpg

David
That was a very nice post.
We know that instrumental records show that there has been a rise in temperature from the 1600’s-lomg before co2 had any effect.
1601 was thought to be the coldest year with the mid 1600’s displaying another cold burst.
This is Co2 plus CET showing linear regression from 1660
http://c3headlines.typepad.com/.a/6a010536b58035970c0120a7c87805970b-pi
The next two are other historic temperature datasets.
http://i47.tinypic.com/2zgt4ly.jpg
http://i45.tinypic.com/125rs3m.jpg
This is where I collect them. Michael Mann had his hockey stick upsaide down as he should have been showing a rise from around 1600. Instead he has inverted the graph to show temperatures falling until the sudden upsurge around 1880.
This simply isn’t what happened according to instrumental records and observations.
Tonyb
http://climatereason.com/LittleIceAgeThermometers/