Scientists shine new light on role of Earth’s orbit in the fate of ancient ice sheets

Posted: May 27, 2022 by oldbrew in climate, Cycles, Ice ages, research, solar system dynamics
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A reconstruction of the Anglian ice sheet in Precambrian North London (credit: BBC / The Natural History Museum, London)


They claim this solves the so-called 100,000 year problem described by Wikipedia:
‘The 100,000-year-problem refers to the lack of an obvious explanation for the periodicity of ice ages at roughly 100,000 years for the past million years, but not before, when the dominant periodicity corresponded to 41,000 years. The unexplained transition between the two periodicity regimes is known as the Mid-Pleistocene Transition, dated to some 800,000 years ago.’ [41,000 years being the approximate obliquity cycle period]

– – –
In a new study published today in the journal Science, the team from Cardiff University has been able to pinpoint exactly how the tilting and wobbling of the Earth as it orbits around the Sun has influenced the melting of ice sheets in the Northern Hemisphere over the past 2 million years or so.

Scientists have long been aware that the waxing and waning of massive Northern Hemisphere ice sheets results from changes in the geometry of Earth’s orbit around the Sun, says Phys.org.

There are two aspects of the Earth’s geometry that can influence the melting of ice sheets: obliquity and precession.

Obliquity is the angle of the Earth’s tilt as it travels around the Sun and is the reason why we have different seasons.

Precession is how the Earth wobbles as it rotates, much like a slightly off-center spinning top. The angle of this wobble means that sometimes the Northern Hemisphere is closest to the Sun and other times the Southern Hemisphere is closest, meaning that roughly every 10,000 years one hemisphere will have warmer summers compared to the other, before it switches.

Scientists have determined that over the past million years or so, the combined effects of obliquity and precession on the waxing and waning of Northern Hemisphere ice sheets has resulted, through complicated interactions within the climate system, in ice age cycles lasting approximately 100 thousand years.

However, before 1 million years ago, in a period known as the early Pleistocene, the duration of ice age cycles was controlled only by obliquity and these ice age cycles were almost exactly 41,000 years long.

For decades, scientists have been puzzled as to why precession did not play a more important part in driving ice age cycles during this period.

In their new study, the Cardiff University team reveal new evidence suggesting that precession did actually play a role during the early Pleistocene.

Their results show that more intense summers, driven by precession, have always caused Northern Hemisphere ice sheets to melt, but before 1 million years ago, these events were less devastating and did not lead to the complete collapse of ice sheets.

Full article here.

Study: Persistent influence of precession on northern ice sheet variability since the early Pleistocene.

Comments
  1. Ned Nikolov, Ph.D. says:

    This new research delivers just more of the same confusion on the topic of what has caused the Ice Ages. When a hammer is the only tool one has, every problem encountered tends to look like a nail, which leads to nowhere in terms of finding a correct solution!

    The key to understanding the drivers of Ice Ages lies outside of the Milankovitch orbital cycles. We have clearly shown this through our research. See this recent blog article:

    Ned Nikolov: Dispelling the Milankovitch Myth

    and watch this video presented at the 101st AMS Annual Meeting in January, 2021:

  2. […] Scientists shine new light on role of Earth’s orbit in the fate of ancient ice sheets […]

  3. gymnosperm says:

    What about eccentricity, the only cycle that actually changes net insolation?

  4. oldbrew says:

    According to some…

    ‘There are three major factors that contribute to Milan-kovitch cycles, namely: 1) precession of Earth’s axis; 2) obliquity or tilt of Earth’s axis; and 3) changing eccentricity of Earth’s orbit’

    ‘The change from lower to higher eccentricity happens every 413,000 years.’

    https://www.encyclopedia.com/environment/energy-government-and-defense-magazines/milankovitch-cycles

    But…

    ‘For example, in 1992, what paleoclimatologists term the “causality problem” appeared—namely, the observation that at least some of the effects that were attributed to changes in Earth’s orbital condition seem to have occurred before the orbital changes.’

    And…

    ‘one well-known problem with Milankovitch theory is that the climate changes observed on the 100,000-year cycle are too strong to be explained by orbitally forced changes in insolation; that is, the changes in how much energy Earth receives from the sun are not large enough, by themselves, to explain the observed cooling and warming.’

  5. Graeme No.3 says:

    old brew:
    I thought that the eccentricity of the Earth’s orbit (100,000 year cycle) resulted in a 6% increase in solar energy for the Earth. Given the claims that the minor increase calculated due to “CO2 trapping heat” would be a disaster, I would have thought that this 6% would cause massive changes.
    I suppose I am confused by the various length of the cycles – I have seen 25,800 by astronomers and 25,000. 23,000, 22,000, 20,000 and 19,000 (even a 17,000 fiddle) by climatologists for the precession cycle (which was first identified by Hipparchos around 150 B.C. so may be considered SETTLED SCIENCE). The Obliquity cycle seems settled as even the climatologists agree with astronomers about 41,000 years length. Eccentricity seems to have varied somewhat with times ranging between 95, 100, 105, 110 and 125 thousand years.
    As for the longest cycle I understood that geologists using nuclear isotopic dating of volcanic residues in the mid-late Triassic decided on a timing (reported) of 405, 414 or 440 thousand years for climate changes. And I thought that the Devil’s Hole datings were for 141 to 147,000 years ago.
    I get the feeling that “THE SCIENCE ISN’T SETTLED’ and my faith in Man Made Climate Change is weakening. Can you restore it?

  6. Ned Nikolov, Ph.D. says:

    Graeme,

    Please read this article based on the best available data we have in terms of orbital variations and Ice Age conditions and cycles:

    https://tallbloke.wordpress.com/2022/01/03/ned-nikolov-dispelling-the-milankovitch-myth/

    The 6% change in TOA solar irradiance due to variations in eccentricity is incorrect! Eccentricity only results in very small variations in solar energy reaching the Earth, in the order of 1.5 W m-2. This has inconsequential effect on global temperature.

  7. oldbrew says:

    The ~25,800 year precession is that of the Earth’s axis, related to obliquity (but not the obliquity period).
    https://en.wikipedia.org/wiki/Axial_precession

    That article also talks about other types of precession, but as Graeme says it’s all quite confusing and the terminology sometimes depends on whose description you’re reading.

    The precession of the perihelion, aka apsidal precession is one of them (~112,000 years).
    https://en.wikipedia.org/wiki/Apsidal_precession

    Combined precession comes in at ~21,000 years in theory, but may be bi-modal (~19000 and ~23000). Then the 112 kyr period is the beat period of the 19 and 23 kyr periods.

    We tried to make some sense of it in the main diagram here.

    Orbital resonance and the celestial origins of Earth’s climatic changes – Why Phi?

  8. Phoenix44 says:

    My understanding was that obliquity is poorly understood and not necessarily a clear cycle? It is very difficult to predict obliquity and is an area that seems to be ignored often enough because its too difficult.

  9. oldmanK says:

    Phoenix44 is right, more than right.

    The precession of the earth’s rotating axis is dependent on obliquity, the angle of tilt of the axis relative to the plane of the ecliptic (and the main/major gravity source). This was raised in the past at this site here: https://tallbloke.wordpress.com/2015/11/09/z-axis-theory-gets-a-boost-from-a-study-of-gyroscopic-precessional-motion/

    And it has bedevilled me ever since.

    It now appears that the ecliptic plane can be shifted some by the influence of primarily Jupiter; see here https://iopscience.iop.org/article/10.3847/1538-3881/ab5365/pdf

    This new data does not indicate a change of obliquity with respect to free space, but – if I understand correctly- a disturbance of the ecliptic plane such that the earth’s orientation to the sun changes during its orbit. Part quote “with some stable solar system variants featuring
    oscillations in Earth’s orbital inclination that approached, or even
    exceeded, ten degrees.”

    Another factor is that the influence of Jupiter, plus Saturn and Venus (and the moon) appear to effect the earth obliquity as well. This was inadvertently proven by the Chinese astronomers in year 173CE when measuring earth’s tilt (and disagreeing among themselves and with the previous and later measurements – they did not know what was happening, precisely because such effect occurs within days). This had been considered by later researchers as ‘poor work’. Only the effect of that obliquity disturbance in that year left a clear trace in the ablation of glaciers and lake sedimentation.

    Meaning that obliquity can, and has been changing abruptly for millennia, with collateral great climatic changes. And with it changes in precession of the earth’s axis of rotation.

  10. Jim says:

    Actually, wrong. Okay, start with a ball, if, it has a cover, that stays in place, it reproduces the results they talk about. But, our ball cover moves in it’s relationship to it’s center, subduction, continental drift. The ball cover moves relative to the center. Some of the landmasses, move or even disappear. Some of them create more landmasses or join to others, changing the relative center of masses. Like usual, they ignore yesterday, saying there was no day before yesterday.

  11. Graeme No.3 says:

    Thanks all for comments. Ned, for some reason your Youtube wouldn’t start, probably a problem with my WiFi as I have now been able to record it for study.
    Jim, I have lost the reference but many years ago (pre internet) the State Astronomer for South Australia George Dodwell (indeed the only one ever) commented on the alignment of (from memory) the Temple of Karnak in ancient Egypt being different from what would be now thought correct. He postulated that something had altered the relationship between the Earth and the stars.

  12. Graeme No.3 says:

    oldbrew:
    That was a hell of a discussion and above my intellectual level. I would point out that there was wide spread troubles around that time. The Skara Brae (or Ness of Brodgar from recent excavations) in Orkney seems to have ended around 2300 BC. Work on Stonehenge seems to have stopped about 2250 B.C. and not resumed until around 1500 B.C.The collapse of the Old Kingdom in Egypt occurred about that time, and there were a series of short llived dynasties. The Sumerian age in Mesopotamia was replaced by the Akkadian empire about 2400BC, which in turn collapsed fairly quickly around 2200BC, and the rise of Babylon was hundreds of years later. There was the disappearance of an early Chinese State about the same time. The end of the Harrapan State is thought to have been later, (about 1900B.C.) after the Indus river moved about 6 km.
    It would seem something went wrong with the climate around that time. And several of those States were known to be very interested in astronomy.

  13. oldbrew says:

    My own guess is that rising sea level played a big part in the demise of Brodgar and Skara Brae. The abandonment of Brodgar suggests an organised closedown event may have taken place.

  14. Ned Nikolov, Ph.D. says:

    Couple days ago, I sent the following email to the authors of the paper discussed in this blog post (Persistent influence of precession on northern ice sheet variability since the early Pleistocene: https://www.science.org/doi/10.1126/science.abm4033). I’ll let everyone know, if I receive a reply:

    ———————————————

    Dear Prof. Barker and Co-authors,

    I recently came across your paper in Science “Persistent influence of precession on northern ice sheet variability since the early Pleistocene“. I appreciate your research in trying the reconcile the role of precession and obliquity as drivers of Ice Ages for the past 1.7 million years! You approached the problem from a standpoint of ice-volume dynamics as observed in higher latitudes of the Northern Hemisphere. However, reconstructed changes of global temperature over the past 800 ky using oxygen 18 isotope as a proxy do not show a meaningful relationships with any known parameters of the Milankovitch cycles. See for example this recent blog article illustrating the lack of such relationships with graphs:

    Dispelling the Milankovitch Myth“:
    https://tallbloke.wordpress.com/2022/01/03/ned-nikolov-dispelling-the-milankovitch-myth/

    Specifically, there are several observed paleo-climatic phenomena that the Milankovitch orbital cycles (of obliquity, precession, and eccentricity) and the current CO2-based climate theory cannot explain:

    1. Glacial cycles are synchronous between Northern and Southern Hemisphere, i.e. they occur simultaneously and in phase on both Hemispheres;

    2. Known eccentricity variations of Earth’s orbit around the Sun only slightly change the Earth’s mean annual distance to the Sun resulting in very small annual variations in Total Solar Irradiance (TSI) at the top of the atmosphere for the past 2 million years that are practically inconsequential for global temperature;

    3. Although Earth’s mean annual distance to the Sun has not changed in any significant way during the past 800 – 1700 ky, Earth’s equatorial surface temperature shows pronounced variations of 4-5 K during glacial cycles. These variations cannot be explained by obliquity or precession cycles, because the tropics have always been far away from any large glaciers or continental ice-sheets forming during periods glaciations. In other words, the question is, why do the Earth’s tropics get 4-5 K cooler at glacial maxima?

    4. The ice-age cycles of the past 800 ky are characterized by strong polar amplifications, a phenomenon, which refers to the fact that, during glacial-interglacial cycles, the amplitude of change in polar surface temperatures is more than 2 times larger than the amplitude of change in tropical surface temperatures. The much larger temperature variations at the Poles compared to those at the Equator are a hallmark of Earth’s paleoclimate that is observed not only during the Pleistocene, but for earlier epochs as well such as the early Eocene, when there was no ice on the surface of Earth… To my knowledge, no climate model can successfully reproduce the observed polar amplifications in the geological records of the Pleistocene or any other paleoclimatic period.

    You might be interested to know that there is a new concept that explains Earth’s paleoclimate including the Pleistocene ice ages based on a fundamentally different understanding of the Atmospheric Thermal Effect (ATE) currently known as the “greenhouse effect”. See Nikolov & Zeller 2017 (https://www.omicsonline.org/open-access/New-Insights-on-the-Physical-Nature-of-the-Atmospheric-Greenhouse-Effect-Deduced-from-an-Empirical-Planetary-Temperature-Model.pdf) for a description of ATE. This new Paradigm about drivers of Earth’s paleoclimate was presented at the 101st AMS Annual Meeting in Jan, 2021. You can watch our video presentation at that event:

    Implications of a Semi-empirical Planetary Temperature Model for a New Understanding of Earth’s Paleoclimate History and Polar Amplification“:
    https://www.youtube.com/watch?v=DpUkPPtkPVc

    I’d be happy to answer any questions you may have regarding this new science.
    —————————————————-

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