CO2: Ice Cores vs. Plant Stomata

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 the cann 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 (~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…

What happens if we use the plant stomata-derived CO2 instead of the ice core data?  The CO2 chart is from Kouwenberg, 2004. It a reconstruction of atmospheric CO2 from plant stomata. It clearly shows that pre-industrial CO2 levels routinely fluctuated from ~280 to 310-360ppmv. The post-800 AD data were also published in Kouwneberg et al., 2005. Dr. Kouwenberg attributed the 400-600 AD CO2 maximum to unspecified local environmental stresses because the high CO2 level could not be matched up with climate warming… She was relying on Mann & Jones, 2003 reconstruction. I used the temperature reconstructions from Moberg et al., 2005 and Ljungqvist 2010; neither of which was available at the time Dr. Kouwneberg published these CO2 reconstructions.

We find that the ~230-year lag time is consistent. CO2 levels peaked ~230 years after the Medieval Warm Period peaked and the Little Ice Age cooling began and CO2 bottomed out ~230 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 230 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…

Mcelwain et al., 2002 found that a “~77 ppm decrease in atmospheric CO2 at the onset of the Younger Dryas stadial… lagged climatic cooling by ~130 yr.”   The stomata data clearly support a temperature-driven carbon cycle.

Once dissolved in the deep-ocean, the residence time for carbon atoms can be more than 500 years. So, a 150- to 250-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 up to 36ppmv.
  • Modern satellite data show that atmospheric CO2 levels in Antarctica are up to 20ppmv lower than temperate and tropical 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 much lower than the Antarctic ice cores indicate.

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.

Mcelwain, J. C., Mayle, F. E. and Beerling, D. J. 2002. Stomatal evidence for a decline in atmospheric CO2 concentration during the Younger Dryas stadial: a comparison with Antarctic ice core records. J. Quaternary Sci., Vol. 17 pp. 21–29. ISSN 0267-8179.

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.

Ljungqvist, F.C. 2010. A new reconstruction of temperature variability in the extra-tropical Northern Hemisphere during the last two millennia. Geografiska Annaler: Physical Geography, Vol. 92 A(3), pp. 339-351, September 2010.  DOI: 10.1111/j.1468-0459.2010.00399.x

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22 Responses to “CO2: Ice Cores vs. Plant Stomata”

  1. Merry Christmas, Global-Warming Cultists! « Public Secrets Says:

    […] my present to you: research showing that CO2 levels in the atmosphere are consistent with the warming and cooling of the oceans, with about a 250-year lag: We find that the ~250-year lag time is consistent. CO2 levels peaked […]

  2. John O'Sullivan Says:

    David,
    Dr Tim Ball has drawn my attention to this superb analysis. Would you be available to contribute one or more chapters on this subject as part of our ‘Slaying the Sky Dragon’ book project? We are looking for new material for the next book in this series due to be published in April 2011. Please get back to me as soon as you can if this interests you.
    Regards,
    John O’Sullivan
    Project Leader

    • David Middleton Says:

      John,

      I’m extremely flattered by Dr. Ball’s and your interest in my work. I would be very interested in contributing material to your next book. I would have to check with my employer to see if the company has any policies or concerns… I work in the oil industry for a publicly traded company.

  3. erlhapp Says:

    Your work needs to be widely considered. I hope you use every endeavor to make that happen.

    Looks to me like the oil industry has a strong interest in employing capable people.

    I am not sure that ‘the science’ is of any real concern to those who would limit carbon emissions. But is is important to those who want to be rational in their daily activities and their choice of people who will represent them in government.

    Looks like it will take a while to turn this bandwagon around.

  4. Snow Accumulation Map Says:

    […] […]

  5. Murray Duffin Says:

    Very interesting analysis, especially the evidence of the CO2 time lag. The problem I see is that warming in the ice core records seems to contribute about 10 ppm increase in CO2 per degree C. Maybe 20 ppm at a stretch. We seem to have a considerably greater CO2 increase than could be contributed by average warming. I would guess that the anthropogenic contribution since ca 1850 is near half of the observed increase.

  6. Tom Van Hoof: Historical co2 records « tallbloke's talkshop Says:

    […] Dr Van  Hoof is referring to Dave Middleton’s analysis here: https://debunkhouse.wordpress.com/2010/12/25/co2-ice-cores-vs-plant-stomata-wuwt/ […]

  7. Antarctic Ice Cores: The Sample Rate Problem | Watts Up With That? Says:

    […] first guess post (CO2: Ice Cores vs. Plant Stomata), we discussed the merits of ice cores vs. plant stomata as paleo-CO2 measurements. One of the key […]

  8. A. Semczyszak Says:

    It is worth to take advantage of the revised Beck’s diagram, a new graph:
    (background validation by: Massen and Beck, 2009. Accurate estimation of CO2 background level from near ground measurements at non-mixed environments.)

    Ice cores – their drawbacks – CO2 – I recommend the discussion here. Sorry is very long …

    Work based on ice cores say about 50 years difference: Frank et al., 2010.: “… with a 50-year CO2 response lag—such timing is consistent with modelled CO2 response to a temperature step change.”

    • David Middleton Says:

      That’s great! Thank you!

      The revised Beck graph looks like a pretty good fit to the model I constructed in my “Diffusion Confusion” post.

  9. Ron Broberg Says:

    This is an interesting post, but it does not support its conclusions. That CO2 lags temperature in natural situations is well understood. That simple, uncontroversial statement does not provide an answer to the question – what happens when we add additional CO2 to the atmosphere from fossil sources?

    • David Middleton Says:

      Which of these conclusions are unsupported?

      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.

  10. Ron Broberg Says:

    Let me expand on that slightly. Looking at the Moberg-Kouwenberg chart, the temp from 1100 to 1600 dropped 0.7C and CO2 responded (roughly 250 years later) by dropping about 30ppm from ~315 to ~285ppm. From 1600 to 1750, temperature had only increased by about 0.1C, but CO2 has “responded” (after a 250 year lag) by increasing to about 360ppm (Kouwenberg) – an increase of about 75ppm.

    So for the whole cooling period: -0.7C/-30ppm -> 0.1C/4ppm
    For the beginning of the modern warming: +0.1C/75ppm

    The current CO2 “response” to the 0.1C rise in temps from 250 years ago (1600-1750) is entirely out of proportion with the CO2 response to the drop in temps during the LIA.

    • David Middleton Says:

      The warming pulse (+0.3C) from ~950AD to ~1140AD was followed by a CO2 pulse from ~1180AD to ~1375AD (~255 to ~320 ppmv)… +65 ppmv. 45 ppmv/ 0.4C = 216.7 ppmv/C.

      There was a warming pulse of +0.3C from 1610AD to 1800AD. At 216.7 ppmv/C, the 1610AD to 1800AD warming pulse should have led to 65 ppmv rise in CO2. CO2 started rising in ~1840AD. By 2010, we should have seen about a 60ppmv rise in CO2 from the 1610 to 1800 warming pulse.

      Assuming that a robust mathematical relationship could be derived from such a few points of data… CO2 would have risen from 280ppmv to 340ppmv without anthropogenic effects.

      From a radiative forcing perspective, the difference between 340 and 390 ppmv is not significant.

      • Ron Broberg Says:

        1800 + 250 years = 2050. Are you now arguing that the lag is only 200-210 years? You cannot include the warming from 1760-1800 if you want to maintain a lag of 250 years.

        So I ask – How long is the lag?

  11. David Middleton Says:

    Ron,

    The warming pulse that began in about 950 AD was followed by a CO2 pulse that began in about 1180 AD… That’s a lag of about 230 years. That warming pulse peaked in about 1140 AD and the CO2 pulse peaked in about 1375 AD… That’s a lag of about 235 years.

    The warming pulse that began in about 1610 AD was followed by a CO2 pulse that began in about 1840 AD… A lag of about 230 years. That warming pulse ended in about 1810 AD. Assuming a ~230-yr lag, the CO2 pulse from that warming event is still ongoing.

    The points at which these pulses begin and end is somewhat arbitrary. When I first plotted this up, I eyeballed the lag to be roughly 250 years. Based on these three points of data, I should have written that the lag was ~230-yrs.

    However, the lag is likely to be quite variable. The lag in the Antarctic ice cores in the Pleistocene glacial cycles can vary from a few hundred to more than 1,000 years. It averages about 800 years.

  12. A response to Middleton: Ice Cores vs. Plant Stomata « The Whiteboard Says:

    […] was latter picked up by WUWT. Learned lots, but the conclusion of the piece is over-reaching. I had a short chat with Middleton about it. It was clear I would have to be more precise to make my […]

  13. Ron Broberg Says:

    I agree that the lag in your Moberg-Kouwenberg chart is more like 235-240 years. Given that, we can divide the era from 770-1745 into four sections, two warming and two cooling, and take a closer look at CO2 response.

    Which is what I did here:
    http://rhinohide.wordpress.com/2011/01/11/a-response-to-middleton-ice-cores-vs-plant-stomata/

    And now I can answer your question about which conclusion is not supported by your presentation. I am taking exception to the claim that “The anthropogenic contribution to the carbon cycle since 1860 is minimal and inconsequential.” I don’t believe you have enough data (not even considering that fact that you have dropped the error bars around the data that you are using) to support that conclusion.

  14. Genghis Khan Methods, Baron Münchhausen Lies, Parcel of Stools as Argument, Mealworm Burgers for Your Last Supper: Warmists » Euro-med Says:

    […] by stomata/preserved plant remnants (right) of atmospheric CO2 correlate very well with Antarctic ice core finds (left), each vertical line here being the turn of a century – beginning with 1000 AD – and […]

  15. Genghis Khan Methods, Baron Münchhausen Lies, Parcel of Stools as Argument, Mealworm Burgers for Your Last Supper: Warmists | Centurean2′s Weblog Says:

    […] by stomata/preserved plant remnants (right) of atmospheric CO2 correlate very well with Antarctic ice core finds (left), each vertical line here being the turn of a century – beginning with 1000 AD – and […]

  16. Dschingis Khan-Methoden, Baron Münchhausen-Lügen, Paket mit Stuhl als Argument, Mehlwurm-Burger als ihr letztes Abendmahl: Warmisten. « Der Honigmann sagt… Says:

    […] von Spaltöffnungen erhaltener Pflanzenreste über atmosphärisches CO2 entsprechen sehr gut Eiskernfunden aus der Antarktis (links) – wobei jede senkrechte Linie hier die Wende eines Jahrhunderts […]

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