Ancient air challenges carbon dioxide explanation for a shift in glacial cycles

Posted: November 3, 2019 by oldbrew in atmosphere, climate, History, Ice ages, research
Tags: , ,

A reconstruction of the Anglian ice sheet in Precambrian North London (credit: BBC / The Natural History Museum, London)

This might rattle a few cages in climate-land.

An analysis of air up to 2 million years old, trapped in Antarctic ice, shows that a major shift in the periodicity of glacial cycles was probably not caused by a long-term decline in atmospheric levels of carbon dioxide, writes Eric W. Wolff in Nature.
– – –
During the past 2.6 million years, Earth’s climate has alternated between warm periods known as interglacials, when conditions were similar to those of today, and cold glacials, when ice sheets spread across North America and northern Europe.

Before about 1 million years ago, the warm periods recurred every 40,000 years, but after that, the return period lengthened to an average of about 100,000 years.

It has often been suggested that a decline in the atmospheric concentration of carbon dioxide was responsible for this fundamental change.

Writing in Nature, Yan et al.1 report the first direct measurements of atmospheric CO2 concentrations from more than 1 million years ago.

Their data show that, although CO2 levels during glacials stayed well above the lows that occurred during the deep glacials of the past 800,000 years, the maximum CO2 concentrations during interglacials did not decline.

The explanation for the change must therefore lie elsewhere.

Understanding what caused the shift in periodicity, known as the mid-Pleistocene transition (MPT), is one of the great challenges of palaeoclimate science.

The 40,000-year periodicity that dominated until about 1 million years ago is easily explained, because the tilt of Earth’s spin axis relative to its orbit around the Sun varies between 22.1° and 24.5° with the same period. In other words, before the MPT, low tilts led to cooler summers that promoted the growth and preservation of ice sheets.

But after the MPT, glacial cycles lasted for two to three tilt cycles. Because the pattern of variation in Earth’s orbit and tilt remained unchanged, this implies that the energy needed to lose ice sheets had increased.

One prominent explanation is that atmospheric levels of CO2 were declining, and eventually crossed a threshold value below which the net cooling effect of the decline allowed ice sheets to persist and grow larger.

Full article here.
– – –
Meanwhile, the team hasn’t stopped its exploration of the blue ice. “It’s conceivable that there’s ice as old, or even older, out there,” Yan says. Next month, a team led by Higgins will arrive in Antarctica to hunt for it. And this time, they’re bringing a bigger

  1. Stephen Richards says:

    This idea that atmospheric gases remain trapped in ice of many thousands of years worries me deeply. Certainly, larger molecules may remain for very long periods but smaller molecules simply must migrate.

  2. oldbrew says:

    Stephen R – the authors do say they ran into trouble with the gases beyond 1.5 million years.

    Unfortunately, in the oldest ice samples, there was evidence that the CO2 concentration had been artificially enhanced by gas produced from the breakdown of organic material at the base of the ice sheet. A few samples from about 2 million years ago were potentially not affected by this issue, but were insufficient in number to allow any conclusions to be drawn about the range of CO2 levels at that time.

  3. JB says:

    Dating accuracy in ice cores out to one MILLION years?

    A uniformitarian perspective on the earth’s obliquity?

    “Studies have shown that at 10,178 BC, or over 12,000 years ago, the celestial pole was inclined at an angle of 30 ° from its present position. P15 “When the Earth Nearly Died” Allan and Delair . “The Laschamp Geomagnetic Event”, Noel, M, and D H Tarling. 1975 Nature, voI 253, pp705-706; see fig 2 on p705.

    Glacial cycles?

    “Inevitably, the length of the Pleistocene epoch hosting these events increased every time writers multiplied the number of separate glacial and interglacial episodes. Thus, initially of modest duration, it steadily lengthened to one or two or more million years. En route to arriving at that situation, all kinds of estimates of the durations of the supposed glacial and interglacial cycles were
    proposed, discussed and, as often as not, discarded. Precise agreement was almost never
    reached. More recently, the great lengths previously advocated for the formation and for
    the waning of these episodes have begun to be queried, and in some cases drastically
    reduced on the basis of new evidence.* Although this aspect of the Ice Age will be examined more fully later, we may nevertheless recall noting earlier that the growth and decay of some of these glacial and interglacial phases proceeded with remarkable rapidity, quite unlike the process imagined by Agassiz, Penck, Geikie and most earlier glacialists, and quite at variance with the
    gradualism enshrined in Lyell’s famous theory of uniformity.

    Thus, through an uneasy mixture of field discoveries, inferences and presumptions, was born the concept of an Ice Age occupying an ever-lengthening Pleistocene period. By now, of course, it will be evident that the whole edifice of the Ice Age of orthodoxy rests upon very shaky ground. That is not to assert that the Ice Age did not exist, but does indicate that it occurred in a form and by a
    means not properly accommodated by conventional dogma. Moreover, a serious error down the years has been the general acceptance by most older (and many present) glaciologists that the Ice Age, whatever its origin, character and duration, developed and ran its course in a world topographically similar to that of today. As we shall now see, that too was a fallacy, and that the implications of that conclusion are huge and very far reaching.” P25

    Considering the shaky alliance between assumptions, conjecture and a misconceived topographical background long embodied in orthodox Ice Age discussion, it is little wonder that all these explanations have failed to account for all aspects of the so-called Ice Age enigma, In their present
    form they are incapable of doing so.” pp39-39 “When the Earth Nearly Died” Allan and Delair

  4. oldmanK says:

    JB, thanks for the tip re the Allan and Delair book. Leafed thru once but looks worth thorough reading.

    In the past 20 yrs+ a lot more material came to light that would support the above extracts. Also some ideas would need updating. For example there have been many studies on tectonic rotations, which would put a different perspective on any paleomagnetic research.

    As for earth tilt change – !!!!(I won’t go into that again). However it is evident science act much in the same way as ‘established’ religion, where the biggest sin is rocking the dogmatic boat.

  5. oldbrew says:

    Another version of the story here…

    World’s oldest ice core could solve mystery of ‘flipped’ ice age cycles
    By Paul Voosen Oct. 30, 2019

    When the team looked at CO2 levels from 1.5 million years ago, they found them on average quite similar to the postflip world, swinging between 204 and 289 ppm, depending on whether the world was in an ice age or not. “It’s surprising,” Yan says, given broad evidence that the world was warmer in the early Pleistocene, before the ice ages grew deeper. “The educated guess is you’d have higher CO2 to achieve that. But that’s not something we see.”

    That means that something other than a long-term CO2 decline was likely driving the cooling, says Peter Clark, a glaciologist at Oregon State University in Corvallis. [bold added]
    – – –
    CO2 not driving anything. Will the supposed experts ever give up with their ‘educated guess’ that it does do so?
    Re. the validity of the data:

    Given its limitations, including a small amount of material collected by a narrow drill, the Allan Hills core is unlikely to settle debate on the ice age transition. However, its data are helping calibrate other, indirect methods of measuring ancient CO2, like using isotopic shifts in single-celled foraminifera fossils. As those methods have improved, their estimates have lined up with the new findings. “It’s a wonderful confirmation that the proxies are really working,” Hönisch says.

  6. oldbrew says:

    Wikipedia due for an update?

    Some believe that the strength of the orbital forcing is too small to trigger glaciations, but feedback mechanisms like CO2 may explain this mismatch.'s_orbit_(Milankovitch_cycles)

  7. Stephen Richards says:

    oldbrew says:
    November 3, 2019 at 7:49 pm
    Stephen R – the authors do say they ran into trouble with the gases beyond 1.5 million years.

    Oh only 1.5 million years ! :))


    The doubts about the Milankavic cycles forcing have been around for a while bvut have mostly been promulgated by the CAGW crowd as far as I can tell. However, no one has yet found an obvious mechanism for ice ages and the change from 40000 to 100000 year cycles is also not found.

    I just think we are a very long way from understanding the climate and the concentration on model controlled by CO² is not helping the effort

  8. Ian W says:

    The claim of ‘ancient air trapped in bubbles’ is almost certainly not true. The pressure in the ice at that depth will compress any ‘bubbles’ into the ice, so these are more likely bubbles caused by gases during decompression. Research has also shown that there is significant diffusion of soluble gasses such as CO2

    One common assumption in interpreting ice-core CO 2 records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO 2 diffusion coefficient in ice has not been accurately determined in the laboratory. In this study we take advantage of high levels of CO 2 associated with refrozen layers in an ice core from Siple Dome, Antarctica, to study CO 2 diffusion rates. We use noble gases (Xe /Ar and Kr /Ar), electrical conductivity and Ca 2+ ion concentrations to show that substantial CO 2 diffusion may occur in ice on timescales of thousands of years. We estimate the permeation coefficient for CO 2 in ice is $ $4 Â 10 –21 mol m –1 s –1 Pa –1 at –238C in the top 287 m (corresponding to 2.74 kyr). Smoothing of the CO 2 record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of $930–950 m ($60–70 kyr) indicate that smoothing of the CO 2 record by diffusion in deep ice is comparable to smoothing in the firn. Other types of diffusion (e.g. via liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified.

  9. oldbrew says:

    Pacemaking the Ice Ages by Frequency Modulation of Earth’s Orbital Eccentricity
    J. A. Rial

    Science 23 Jul 1999:
    Vol. 285, Issue 5427, pp. 564-568
    DOI: 10.1126/science.285.5427.564

    Evidence from power spectra of deep-sea oxygen isotope time series suggests that the climate system of Earth responds nonlinearly to astronomical forcing by frequency modulating eccentricity-related variations in insolation. With the help of a simple model, it is shown that frequency modulation of the approximate 100,000-year eccentricity cycles by the 413,000-year component accounts for the variable duration of the ice ages, the multiple-peak character of the time series spectra, and the notorious absence of significant spectral amplitude at the 413,000-year period. The observed spectra are consistent with the classic Milankovitch theories of insolation, so that climate forcing by 100,000-year variations in orbital inclination that cause periodic dust accretion appear unnecessary.

  10. oldbrew says:

    IW: see comment – November 4, 2019 at 8:35 am under ‘validity of the data’.
    – – –
    Another well-cited study…

    On the structure and origin of major glaciation cycles
    2. The 100,000‐year cycle

    J. Imbrie A. Berger E. A. Boyle S. C. Clemens A. Duffy W. R. Howard G. Kukla J. Kutzbach D. G. Martinson A. McIntyre
    First published: December 1993 Cited by: 553

  11. stpaulchuck says:

    the whole project comes off as “maybe this or maybe that”. They already noted discontinuities in what should be a continual age with depth along with pollution of the lowest level samples by rotting vegetation and other natural generators in the Earth surface.

    Not very convincing of anything, actually. IMAO.

  12. oldmanK says:

    Further to JB’s input above:

    Abrupt deglaciation due to the Milankovitch theory does not hold, since change on a ~100kyr basis as per the last five cycles is extremely slow.

    On the other hand the question of tilt change that is given importance in the Allen-Delair book has never been looked into satisfactorily. Last September this item relating to the Dzhanibekov Effect appeared on Youtube
    The original is here:

    Those are the curious dynamics of a rotating object with different inertias along xyz axes. There are no external torques imposed, and its moment of inertia maintains same orientation in spite of body flips. But an oblate body in space orbiting the sun like earth is, experience a torque due to centrifugal force not on same line with centripetal. Plus the Kepler Trigon forces. This leads to the question: Are there abrupt gyro effects kicking in perhaps for less than 24 hrs duration with certain/particular planetary alignments? (Plus that apparently gyro forces are still not well understood;
    see )
    ” Thegyroscope theory is the compulsory chapter in the fundamental textbooks of classical mechanics, particularly machine dynamics [8-10]. Nevertheless, the research transactions and textbooks do not fully explain the dynamics and physics of the gyroscope properties and its strange acting forces and motions still remain not adequately clear”.

  13. Bill Treuren says:

    surely the very implication of perturbation from rotting vegetation indicates the sample are not isolated or hermetically sealed as is assumed.

  14. oldbrew says:

    *Abrupt* deglaciation seems unlikely for an ice sheet 3-4 km. thick. A lot of energy is needed to melt so much ice. Of course it depends what timescales are being discussed.

    For example, when melting 1 kg of ice, 333.55 kJ of energy is absorbed with no temperature change.
    – – –
    The 41,000 year cycle was easy to explain with tilt but 100,000 needs (a) different answer(s) obviously. This frequency repeats – on average at least – so ‘one-time’ theories are no use.
    – – –
    Minor point of interest: the giant moons of Saturn and Neptune – Titan and Triton – are both thought to have a tilt cycle of ~60,000 years.

    …which happens to fit our 60,000 year J-S-U model…
    – – –
    Mars has no moon large enough to stabilize its obliquity, which has varied from 10 to 70 degrees.

  15. oldmanK says:

    a)–Quote: -“*Abrupt* deglaciation seems unlikely for an ice sheet 3-4 km. thick. A lot of energy is needed to melt so much ice. Of course it depends what timescales are being discussed.”
    Abrupt is as indicated by the ‘Meltwater pulse 1A’ here That is a lot of MJ that cannot be provided by a cold(?) ocean or any slow orbital change. The most likely is obliquity change; to a low value to permit such extent of ice formation, and a high value to induce fast melt. Which is in fact what the heretic evidence shows.

    b)– “Mars has no moon large enough to stabilize its obliquity,–“. Depends on perspective ( in the sense that mathematical modelling would obey the imposed conditions of the model, but likely not the facts). Earth’s moon is a decent source of gravitational force that in the right place, time, and right conditions of planetary alignment may lead to substantial earth axial change.

    I cannot see (with my allotted grey matter) CO2 as a major player in causing abrupt melt/deglaciation. Neither the lack of CO2 to cause such abrupt heat loss to freeze mammoths as they graze.

    Just ruminating indigestibles.

  16. oldbrew says:

    New research supports link between climate and orbital parameters…

    Changes in high-altitude winds over the South Pacific produce long-term effects

    New findings from the field of Earth history are improving our grasp of climate mechanisms
    Date: November 5, 2019
    Source: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

    In the past million years, the high-altitude winds of the southern westerly wind belt, which spans nearly half the globe, didn’t behave as uniformly over the Southern Pacific as previously assumed. Instead, they varied cyclically over periods of ca. 21,000 years. A new study has now confirmed close ties between the climate of the mid and high latitudes and that of the tropics in the South Pacific. [bold added]

    More details:
    On the basis of sediment cores, the team of researchers investigated precipitation-driven changes in sediment input in the Pacific off the coast of Chile. Assessing the past 1 million years, they identified what are known as precession cycles: changes caused by natural variations in the Earth’s orbital parameters; in this case, cyclical changes in the rotation of its axis that occurred roughly every 21,000 years. Changes in these and other orbital cycles are generally considered to be a major driver for the alternation between extended glacials and interglacials over the past million years.
    . . .
    “Our climate models show that the precipitation changes recorded in the sediment cores are connected to the configuration of high-altitude winds over the subtropical Pacific. In this regard, the division of the high-altitude wind changes into a northern, subtropical branch, a middle branch, and a subpolar branch in the course of the 21,000-year cycle.” [- climate modeller]

    – – –
    Precession of the perihelion is theoretically about 21,000 years:
    20932 anomalistic years = 20933 tropical years (difference of 1 = complete precession cycle)

    This interaction between the anomalistic and tropical cycle is important in the long-term climate variations on Earth, called the Milankovitch cycles. An equivalent is also known on Mars.

  17. oldbrew says:

    NOVEMBER 6, 2019
    Persistent drizzle at sub-zero temps in Antarctica

    Using both ground-based and satellite measurements, researchers recorded drizzle conditions below minus 13 degrees Fahrenheit lasting for more than 7.5 hours at McMurdo Station, Antarctica. Previous reports recorded supercooled drizzle at these temperatures, but only for brief durations. The presence of drizzle over several hours could have some implications for climate model predictions.
    . . .
    Using the simulations, the researchers found that low concentrations of some types of particles suspended in the Earth’s atmosphere, such as sea-salt and dust, were highly conducive to drizzle formation.

    “In Antarctica, the air is very clean,” said Silber. “There are fewer pollutants, and therefore fewer airborne particles.”

    The low concentration of these particles allowed the drizzle to remain in liquid form, even though the air temperatures were well below freezing.

  18. oldmanK says:

    That drizzle came from water vapour that had condensed and released about 2,260 kJ/kg, (heat of vaporization of water). It need to release a further 333.55 kJ/kg at zero deg temp to freeze.
    Why would it be abnormal?

  19. oldbrew says:

    oldmanK – ‘minus 13 degrees Fahrenheit ‘ is -25 Celsius.

    Paper abstract:

  20. oldmanK says:

    oldbrew _ Yes. What I was driving at is: Is -25C the ambient temp or the temp of the drizzling droplets? (similar argument as why a jet of superheated steam is still dangerous even in a freezing downpour; a matter of thermal transfer).

  21. oldbrew says:

    Paper title: Persistent Supercooled Drizzle at Temperatures Below− 25° C Observed at McMurdo Station, Antarctica

    Ambiguous. Timed out loading abstract :/
    [update: see last quote below]

    From a search engine:
    The temperatures in the drizzle‐producing cloud were below ‐25°C and the drizzle persisted for a period exceeding 7.5 hours.

    NASA version:
    Silber et al. 2019
    Silber, I., A.M. Fridlind, J. Verlinde, A.S. Ackerman, Y.-S. Chen, D.H. Bromwich, S.-H. Wang, M. Cadeddu, and E.W. Eloranta, 2019: Persistent supercooled drizzle at temperatures below -25°C observed at McMurdo Station, Antarctica. J. Geophys. Res. Atmos., early on-line, doi:10.1029/2019JD030882.

    The rarity of reports in the literature of brief and spatially limited observations of drizzle at temperatures below -20°C suggest that riming and other temperature-dependent cloud microphysical processes such as heterogeneous ice nucleation and ice crystal depositional growth prevent drizzle persistence in cold environments. In this study, we report on a persistent drizzle event observed by ground-based remote-sensing measurements at McMurdo Station, Antarctica. The temperatures in the drizzle-producing cloud were below -25°C and the drizzle persisted for a period exceeding 7.5 hours. Using ground-based, satellite, and reanalysis data we conclude that drizzle was likely present in parts of a widespread cloud field, which stretched more than ∼1000 km along the Ross Ice Shelf coast. Parameter space sensitivity tests using two-moment bulk microphysics in large-eddy simulations constrained by the observations suggest that activated ice freezing nuclei (IFN) and accumulation-mode aerosol number concentrations aloft during this persistent drizzle period were likely on the order of 0.2 L-1 and 20 cm-3, respectively. In such constrained simulations, the drizzle moisture flux through cloud base exceeds that of ice. The simulations also indicate that drizzle can lead to the formation of multiple peaks in cloud water content profiles. This study suggests that persistent drizzle at these low temperatures may be common at the low aerosol concentrations typical of the Antarctic and Southern Ocean atmospheres.
    – – –
    This looks better:
    Based on the observational and model analyses, the aerosol conditions necessary for such supercooled drizzle can occur simultaneously with atmospheric temperatures below -25 °C and above the homogeneous freezing temperature regime around winter and summer months near the Antarctic coasts and the inner Antarctic continent, respectively, as well as over the Southern Ocean, particularly during austral winter. This study, therefore, suggests that persistent supercooled drizzle formation events may be rather common over Antarctica and the Southern Ocean. [bold added]

  22. oldmanK says:

    oldbrew: your second link is interesting, however it still leaves me a puzzled skeptic. Looking closely at the pic, here: , is the ‘remote sensing’ apparatus seeing a thermodynamic process in action? Is it seeing two phase changes in action as kJ are being lost from vapour to water, and to ice? Isn’t there some ‘residence time’ of the liquid phase?

  23. oldbrew says:

    We only have the summary, referring to ‘persistent drizzle over 7.5 hours from a shallow, mixed-phase cloud layer with temperatures ranging between -25°C at cloud base and -29°C at cloud top.’

    What ‘mixed phases’ do they mean?

    UPDATE: try this…

    Click to access downloadSupplement

    [23 pages]
    Journal of Geophysical Research: Atmospheres
    Supporting information for
    Persistent Supercooled Drizzle at Temperatures below -25°C Observed at
    McMurdo Station, Antarctica
    – – –
    Comparison of Antarctic and Arctic Single‐Layer Stratiform Mixed‐Phase Cloud Properties Using Ground‐Based Remote Sensing Measurements

    Damao Zhang Andrew Vogelmann Pavlos Kollias Edward Luke Fan Yang Dan Lubin Zhien Wang
    First published: 30 August 2019

  24. phil salmon says:

    This excellent study by Y Yan et al gives a valuable snapshot of CO2 levels back about 2 million years by meticulous and painstaking analysis. This result casts doubt on the hypothesis of CO2 causation and indicates the explanation for the MPT (MPR) lies elsewhere.

    Milankovitch pacing (even if we don’t call it “forcing”) of the Pleistocene glacial wavetrain is sufficiently well established, along with tectonic continental drift, for it not to be worthwhile to continue to debate it. It’s more a factual observation than a hypothesis anyway. Every one of the 30 or so interglacials in the Pleistocene have occurred 6500 years after an obliquity peak, showing ocean heating of obliquity with the expected thermal lag (how long it takes to move ocean temperatures). What are the chances of all those 30 coincidences? Here are the post MPR interglacials plotted with 6500-year lagged obliquity (thanks to Javier):

    The best way to describe the alternation of glacials and interglacials is as “flicker” between two states that represent chaotic attractors. What if climate was slowly descending from a warmer, non glaciated state before the Quarternary to a state of deep permanent glaciation in future – something similar to the Saharan-Andean glaciation 450 Mya or the Sturtian and Marinoan glaciations 640-800 Mya? During the slow transition to the deep glacial state, flickering between warm and cold attractors will occur while the trajectory of the climate in its phase space feels a similar pull from both attractors. While the pull of both attractors is very similar, the system is finely balanced and a very weak forcing such as obliquity is sufficient to tip the system periodically between attractors. This state of affairs is well known and is called a periodically forced nonlinear oscillator. Look up references for example to periodically forced versions of the Belousov-Zhabotinsky spontaneously oscillatory reaction.

    However eventually the flicker stops. Before stopping it will slow down as it starts to feel the cold attractor more strongly than the warm. This has been the case ever since the MPR. Extraordinary that people still call it a mystery – it’s so obvious in the context and paradigm of chaotic attractors. Post MPR, obliquity alone is not enough to precipitate an interglacial. Now all the ducks need to line up – all three Milankovitch oscillations need to peak together – obliquity, precession (and modulation of precession) and eccentricity. (All these are really just different faces of the same thing.) When all Milankovitch cycles peak together – roughly every 100,000 years, only then is the forcing enough to start a new interglacial.

    Looking at this trend of slowing down flickering between two attractors, what comes next? The flickering stops and we enter permanent deep glaciation.