Ice ages driven by Earth orientation changes not co2

Posted: May 28, 2011 by tallbloke in Astrophysics, climate, solar system dynamics

I have thought for years that the Milankovitch cycles, the cyclic changes in the Earth’s orientation and orbital parameters, had a lot to do with the coming and going the Earth’s ice ages. But until I came across this paper today, I had only seen graphs which show a vague correspondence between ice volume and these cycles.

This paper from 2006 put’s the question beyond doubt. Instead of looking at ice volume or extent, it looks at the rate of change of ice volume. And what drives the changes in the Earth’s orientation and orbital parameters which give rise to the Milankovitch cycles? Jupiter, along with the other gas giants, and Venus affect the eccentricity of Earth’s orbit, and our Moon and Sun affect obliquity and precession. More details here. Once again we are finding that it is solar system dynamics which primarily govern changes to climates on Earth, not trace gas quantities. Note however, that co2 could make some difference to the amplitude of the temperature swings between glacial and interglacial coditions, although I would expect changes in atmospheric water vapour levels would make a much bigger difference.

In Defense of Milankovitch
Gerard Roe
GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L24703, doi:10.1029/2006GL027817, 200
Received 9 August 2006; accepted 3 November 2006; published 21 December 2006



Atmospheric CO2 has also been suggested as driving
changes in global ice volume [e.g., Shackleton, 2000; Lea,
2004]. The concentration of CO2 varied between about 200
and 280 ppmv over the last several ice age cycles, and
caused approximately 2 Wm^2
variations in surface longwave radiation forcing
[e.g., Ramaswamy et al., 2001].
Comparisons of the impacts of shortwave and longwave
radiative forcing appropriate over the ice sheets are not
straightforward, but taking summer half-year insolation
variations in shortwave (Figure 3), and assuming an albedo
of 0.5 for melting ice, variations in summertime shortwave
forcing exceed the direct CO2
radiative forcing by about a
factor of five.
It has also been reported that the ice volume
lags behind CO2
, and this has led to the suggestion that CO2
variations drive ice age cycles [Shackleton, 2000; Lea,
2004; Ruddiman and Raymo, 2003]. However, crossspectral
analyses in Figure 4 (and lag correlations, auxiliary
materials) show that, at frequencies where there is significant
coherence between the records, atmospheric CO2 lags,
or is at most synchronous with, dV/dt. In other words,
variations in melting precede variations in CO2. Thus, the
relatively small amplitude of the CO2 radiative forcing and
the absence of a lead over dV/dt both suggest that CO2
variations play a relatively weak role in driving changes in
global ice volume compared to insolation variations. This
certainly does not rule out CO2 as a primary cause of
tropical or other climate variations, or of the apparent
synchronization of the ice-age signal between hemispheres
[Lea, 2004]. We note though that dV/dt contributes both to
the rate of freshwater input into high latitude oceans
(changes in which have been argued to cause global climate
signals), and also to the rate of sea level rise (with a
worldwide destabilizing tendency on ice shelves and coastal ice
masses).
The available evidence supports the essence of the original
idea of Ko¨ppen, Wegner, and Milankovitch as expressed
in their classic papers [Milankovitch, 1941; Ko¨ppen and
Wegener, 1924], and its consequence: (1) the strong
expectation on physical grounds that summertime insolation is
the key player in the mass balance of great Northern
Hemisphere continental ice sheets of the ice ages; and
(2) the rate of change of global ice volume is in antiphase
with variations in summertime insolation in the northern
high latitudes that, in turn, are due to the changing orbit of
the Earth.
PDF available here

Comments
  1. Roger Andrews says:

    Hi TB:

    This issue was discussed quite extensively on the Solar Cycles, Ice Ages and Albedo thread last month. My conclusion was that the relationship between NH insolation and ice ages was too sloppy to confirm that insolation changes alone caused the ice ages. (Roe’s Figure 1, for example, shows that only some insolation changes correlate with ice ages.) For this reason I came up with the following alternative theory, which I am reposting here to serve as a vehicle for discussion.

    “We think ice ages are caused by climate change, but it’s actually the other way round. Climate change is caused by ice ages. And ice ages are controlled by the cyclic behavior of the NH ice sheets.

    First, three governing assumptions:

    1. For at least 400,000 of the last 500,000 years the Earth has been in an ice age condition. In other words, ice ages are the norm. We don’t have to explain them. What we do have to explain are the interglacial periods. These, not the ice ages, are the anomalies.

    2. Interglacials occur only in the NH, where ice sheet extent ranges from maybe as much as 30 million sq km during glacial maxima down to a small fraction of that during interglacials. They don’t occur in the SH. Antarctica has been ice-bound for millions of years.

    3. The problem of explaining what causes ice ages therefore comes down to explaining what causes NH interglacials.

    Now the explanation, step by step:

    Step 1: The NH exits an interglacial period and the NH ice sheets begin to advance again. (Note, we don’t have to explain why they advance. Ice ages are the norm. The Earth is simply returning to its natural climatic – or if you prefer, “balanced” – state.)

    Step 2: The NH ice sheets continue to advance for tens of thousands of years. But eventually a point is reached where they become top-heavy, and then they begin to behave like surge glaciers, calving large quantities of ice into the sea once every five or ten thousand years. These “Heinrich Events” (HEs) are identified from ice-borne detritus in sea bed cores, and they are uncorrelated with temperature, CO2, dust, solar activity or any other climatic variable. They’re purely a result of ice sheet dynamics.

    Step 3: HEs are usually not large enough to upset the balance between ice sheet stability and albedo, but eventually we get one that is. The last HE, which occurred about 15,000 years ago, was one. It calved off an enormous amount of ice at the margins of the ice sheets (maybe as much as 10,000 sq km) and the ice that was left couldn’t fill the hole fast enough to offset the warming impacts of the albedo change. So the climate warmed and the ice sheets continued to retreat, and now we are back in an interglacial.

    Step 4: The interglacial ends. How? Straight answer, I don’t know, but the trigger is again probably physical rather than climatic. So for the time being I’m going to stick with the theory that the NH ice sheets start growing again when the Arctic Ocean becomes ice-free and/or when the Northern Baltic and Hudson Bay become dry land.”

    However, according to Roe the end of interglacials also correlates with a decrease in NH insolation, so it seems likely that solar at least makes a contribution.

  2. Doug Proctor says:

    God, not atmospherics, causes lightning, hailstones and hurricanes. Burn the wizard who disagrees!
    The Earth (and the humans-made-in-God’s-images upon it) is the center of the universe. Expel the wizard who disagrees!
    Men are descended from God’s grace, not monkeys. Burn the wizard’s books!
    Man is God-like and controlls the weather, not physics. Prevent the wizard from publishing!

    The chant that authorities, not free-thinkers, understand the truth is consistent. Man has replaced God in power, that is the main difference. And now we try to silence the critics rather than burn them. If you deny a man the right to work and to express himself, you destroy him socially and intellectually, but there is progress in not confining him to a pyre.

    The evolution of ideas suggests that the next phase will be “God/The universe does control the ABSOLUTE weather and climate, but man is SPECIAL in that he can tweak it for good or evil.”

    Al Gore in 2020: no need to shut down the economy, but a new tax directed to “improve” our local climate is still the morally right thing to do.

  3. tallbloke says:

    Hi Roger, thanks for the detailed comment, I missed that thread mostly, due to being overwhelmed with work.

    Before I read it all, let’s sort this one out:
    (Roe’s Figure 1, for example, shows that only some insolation changes correlate with ice ages.)

    I looked from end to end and found wiggles in all the right places. Which epochs do you see failures at? Also, consider that on there timescales, the motion of the solar system through interstellar clouds and areas of higher stellar density may have a bearing on things.

  4. tallbloke says:

    Doug,
    There are always a few anarchists who won’t knuckle under. Good thing for everyone too!

  5. tallbloke says:

    Hi Roger,
    As a detailed reading of the Roe paper reveals, a rapid meltoff or HE will cause sea level change, which will bust up shelves too, leading to albedo reduction, further accelerating the process of deglaciation.

    I suspect reglaciation probably starts with the Milankovitch cycles plus a long run of stratospheric volcanos in the northerly latitudes impeding insolation.

    There is good correlation between volcanic explosivity index and periods of low solar activity too. The situation with precession is that we have a good long time yet before NH winter starts to get noticeably longer and colder (about 2,000 years).

  6. Roger Andrews says:

    TB

    Right now I’m visiting with kids and grandkids in NYC, so it’s not easy to post well-thought-out responses. I’ll try and get back with something more detailed tomorrow. There are a few other comments in the previous thread I want to look up too.

  7. We are at loss until we accept a new paradigm….until then let´s hear “Gong” again

  8. Malaga View says:

    For at least 400,000 of the last 500,000 years the Earth has been in an ice age condition.
    In other words, ice ages are the norm. We don’t have to explain them.

    This statement becomes problematic when you start defining what we know about the last ice age… there were ice sheets in the NH… but not everywhere… most of Alaska and Siberia don’t appear to have experienced the last ice age… and the extent of ice over the Artic Ocean is unknown… some observers think one ice sheet started in North-East Canada and another was centred on Norway… and slowly they converged over time. So unless you invoke Rule 3 – No Explanations I think there is still some explaining to do.

    Take a look at the maps… http://www.iceagenow.com/Ice-Age_Maps.htm and think about some possibilities…

    http://www.iceagenow.com/Ice_age_engulfed_Europe_in_a_matter_of_months.htm

    http://www.terracycles.com/joomla/superstorms.html

    I suspect reglaciation probably starts with the Milankovitch cycles plus a long run of stratospheric volcanos in the northerly latitudes impeding insolation.

    That is my suspicion as well… my guess is that Milankovitch cycles are necessary but not sufficient to trigger an ice age. However, research into the Younger Dryas event is very interesting and there are other possibilities… such as a magnetic reversal and/or thermal airbursts from comets…

    http://craterhunter.wordpress.com/the-planetary-scaring-of-the-younger-dryas-impact-event/a-minnesota-impact-event/

  9. tallbloke says:

    Roger, no problem, say hi to the kids from us.

    Now step away from the computer…

  10. tallbloke says:

    Some good points there MV. I wonder about surface magnetism. Northern Siberia and Northwestern Canada are where the strongest fields are. I wish we had reliable absolute temperature maps to look at.

  11. Anything is possible says:

    I love the “superstorms” theory, but it’s only question of time before some alarmists get hold of it, and start linking their formation to enhanced levels of CO2 in the atmosphere (:-

  12. Tim Channon says:

    I’m having trouble following the paper.

    Ignoring the skating over some awkward problems (there again can we trust the orbital data?) it goes on to show ice volume.

    Surprisingly that is a near clone of Deuterium in EPICA ice core data.

  13. cementafriend says:

    RA’s explanation ignores the effect of clouds. The so-called albedo due to ice is minor compared to changes of clouds. Also, to say that there was no “ice age” in South Hemisphere would appear to be wrong. There is lots of evidence of recent (16,000 year ago) glaciers and ice sheets in NewZealand and Tasmania (Australia). New Zealand still has a number of glaciers the Fox and Franz Josef are two significant and accessable ones. Have not been to South Amercia but am told that there is lots of evidence there in Chile and Argentina

  14. tallbloke says:

    Tim Channon says:
    (there again can we trust the orbital data?)
    it goes on to show ice volume.
    Surprisingly that is a near clone of Deuterium in EPICA ice core data.

    Good question and good sleuthing. I think though, that when two datasets generated from such disparate data match so well, it gives support to the validity of both. Doesn’t it?

    Providing there has been no monkeying about with the data of course. :)

    CaF: Good point about SH glaciation.

    AiP: This paper makes some good points about co2 I think.

  15. tallbloke says:

    Tim, slide 8 on this link says the deuterium values are from Vostok

    http://www.sciencecourseware.org/eec/GlobalWarming/Tutorials/Milankovitch/

  16. Roger Andrews says:

    Hi TB:

    “I looked from end to end and found wiggles in all the right places. Which epochs do you see failures at?”

    Roe Figure 1 shows a period of 20-25,000 years in the insolation data and a period of about 100,000 years in the “ice volume” data. There is always a relationship between ice volume and insolation, but why should every fourth insolation cycle cause an ice age?

    When we look at ice core data the 100,000-year ice age periodicity starts to break up too. The interglacial peaks in the Epica record, for example, occur at 407000, 334000, 242000 and 129000 years BP, giving periods of 73000, 92000, 113000 and 129000 years.

    I don’t dispute that the 100,000 year solar cycle is a major control on the earth’s climate, but to explain ice ages I think we need a physical trigger mechanism as well.

    Higher authority wants the computer. Back later.

  17. tallbloke says:

    Roger:
    Roe Figure 1 shows a period of 20-25,000 years in the insolation data and a period of about 100,000 years in the “ice volume” data. There is always a relationship between ice volume and insolation, but why should every fourth insolation cycle cause an ice age?

    Because it roughly coincides with the 100,000 year orbital eccentricity cycle?

    I agree there are other factors involved. Which ones are your favourites? I like volcanism and cosmic rays.

  18. Roger Andrews says:

    Hi TB:

    “Because it roughly coincides with the 100,000 year orbital eccentricity cycle?” Well yes, but with periods ranging from 73,000 to 129,000 years, it’s getting pretty rough. Unless of course the ice core age dates are screwed up, as discussed in the last thread.

    What I would like to do is compare the Roe orbital period data with some of the DSDP Atlantic seabed core data, but I can’t access these data from here. I’ll give it a shot when I get home next week. :-)

  19. tchannon says:

    If I can get the orbital/insolation data over a sufficient time span I can lock to the details.

    This would be interesting as a compare with the ice data, does it phase match or not?

    I have tried to find this stuff, which turns out to be tricky. Ephemeris generally doesn’t work because most of the published are approximation over a relatively short period.
    I have given up several times.

  20. tallbloke says:

    Hi Tim,
    my guess is that because the eccentricity, azial tilt and precession are governed primarily by Jupiter, Moon and Sun, a simplified ephemeris is calculated, as these bodies are not so much affected by minor perturbations from other planets.

    I suppose we could try emailing Roe to see if he could supply a dataset.

  21. Tim Channon says:

    There are multiple effects, more than just M.

    One of the problems is why a much larger longer cycle is not in the data. Above 100k should be larger, not more or less nothing.

    The possibility of orbital mode switching has crossed my mind: with no observations how can be be sure of much? Consider that non-orbit horseshoe orbit. If that can really happen mass transfer could allow a change in earth orbital distance. Details, I have no idea.

    A search mentions Tamino saying he used Laskar.

    This is an interesting self discussion

    http://translate.google.com/translate?hl=en&sl=de&u=http://www.scienceblogs.de/astrodicticum-simplex/2008/04/chaos-im-sonnensystem.php

    Point at this accessible item

    http://articles.adsabs.harvard.edu/full/2002MNRAS.336..483I

    Leave it at that.

  22. tallbloke says:

    “One of the problems is why a much larger longer cycle is not in the data. Above 100k should be larger, not more or less nothing.”

    Caused by what?

    Overall, the entire galaxy rotates clockwise (as viewed from “galactic north”) at a roughly constant velocity of 160-220 km/sec:

    Relative to this velocity, the Sun and its planetary system move around the galactic center at a velocity of 17-22 km/sec, in a roughly elliptical orbit, with a period of about 240 million years.

    The Sun and its planetary system also move perpendicular to the galactic plane (up and down in a harmonic fashion) with a period of 57-74 million years.

  23. Tim Channon says:

    There is suppposed to be 41, 100, 400k

  24. Tim Channon says:

    I’d forgotten this one. Is probably used by some.

    Compiling Fortran is likely to be fun.

    ftp://ftp.imcce.fr/pub/ephem/sun/la93/

  25. tallbloke says:

    Every 100,000 years, the eccentricity of Earth’s orbit around the Sun oscillates between 0% and 5%.

    Every 41,000 years, the tilt of Earth’s spin axis oscillates between 21.5° and 24.5°.

    Every 23,000 years, the spatial orientation of Earth’s spin axis oscillates between pointing towards Polaris and pointing towards Vega as the North Star.

    What is your 400K year oscillation? Not one of the Milankovitch cycles as far as I’m aware.

    Didn’t the Cheifio compile GISStemp fortran on some old box he has?

  26. Tenuc says:

    Tim Channon says:
    May 30, 2011 at 8:15 pm
    “…Consider that non-orbit horseshoe orbit. If that can really happen mass transfer could allow a change in earth orbital distance. Details, I have no idea…”

    For a good very simple explanation of how the horseshoe orbits can happen have a look at this short paper from Miles Mathis here…

    http://milesmathis.com/aster.pdf

    For fuller information about Lagrange points see here…

    http://milesmathis.com/lagrange2.html

    Things are far less mysterious once the basic physics are understood.

  27. Tim Channon says:

    I don’t see a problem with the orbit. Perhaps I do with a misleading image but there is no image without the viewer having to do some degree of mental gymnastics.

    Unfortunately I can only draw an alternative using a blackboard or paper and pencil, far too hard trying to get computer software to do this. Probably needs human interaction anyway to get the idea across.

    I can try in words.

    1. background

    A plan view of the sun, earth in orbit and a tiny other object in approximately the same orbit as the earth.

    Only gravity is considered.

    Earth planet has a kinetic energy level, is in an orbital radius defined by orbital velocity, interplay of energy/velocity/distance

    Representationally it might be useful to open up one year into a straight line, earth shown twice and gravity off to one side. (your mental choice)

    2. Initial conditions

    Other object is orbiting closer to the sun.

    Therefore it has a greater velocity than the earth.

    3. process

    The object catches up with the earth causing increasing gravitational attraction.

    The object is forced away from the sun to an increased orbital radius causing a tradeoff of velocity, the object slows, ultimately below the orbital velocity of the earth and into a larger orbit than the earth.

    It now falls behind the earth until the opposite conditions apply, the earth is close again causing another orbital switch, back to higher velocity closer to the sun.

    Ad nausium.

    Is the above correct?
    The existence of the object and behaviour is accepted.
    I suggest it is the fringe of chaotic behaviour, warning that numerical instability/defect is likely to be a risk for calculations.
    I suspect this is elliptical similar to conventional but with loci in an unusual place.

    Views

    1. Seen as a solar system plan the object orbit will be the same as the earth plus a slight ripple.

    2. Seen as a straight line, an opened up earth orbit path it wil be an ellipse

    3. If the ellipse is folded around the earth orbit the plan is like a horseshoe.

    This paper might add meat, note figure 4. (compare with Miles)
    If the object is without the forbidden region there is no problem. Forbidden is horseshoe shaped and finite.

    http://www.ieec.fcr.es/libpoint/papers/ross.pdf

  28. Tim Channon says:

    tb:
    “those expected from the Earth’s eccentricity: 95, 125, and 400 k.y”

    http://muller.lbl.gov/papers/geology2.html

    “The mismatch between the 100 and 400 k.y. components of Pleistocene climate and the relative power of those terms from the eccentricity of the Earth’s orbit remains a challenge to the Milankovitch hypothesis.”

    http://www.environment.harvard.edu/docs/faculty_pubs/schrag_chemistry.pdf

    A search will find copious references.

    Sorry if I am pouring cold water but fantasy is not on the menu. Whatever is has to be is although deciding what is real or not can be very hard, dissing papers especially. (wrong papers abound, no mechanism for automatic yanking)

    I assume we are all looking for clarity.

  29. Tenuc says:

    Tim Channon says:
    May 31, 2011 at 3:48 pm
    “…3 process

    The object catches up with the earth causing increasing gravitational attraction.

    The object is forced away from the sun to an increased orbital radius causing a tradeoff of velocity, the object slows, ultimately below the orbital velocity of the earth and into a larger orbit than the earth.

    It now falls behind the earth until the opposite conditions apply, the earth is close again causing another orbital switch, back to higher velocity closer to the sun.

    Ad nausium.

    Is the above correct?…”

    Sorry Tim, but I can’t see your process working. If the asteroid is orbiting quicker than than Earth when it starts to get close it will start accelerating faster as it comes under the influence of our planets gravity. It will, of course, move away from the sun as it is pulled into a wider orbit by the Earth but the acceleration will continue to increase as it gets closer until eventually it will pass or collide. I can’t see how this will result in a long-term stable ‘horseshoe” orbit.

    This problem has triggered another question. Why do so few large asteroids hit the Earth? We can tell by the evidence of large impacts on the moon and other planets that these are fairly common events, so what mechanism prevents Earth being hit more often?

  30. Tenuc says:

    Tim Channon says:
    May 31, 2011 at 4:02 pm
    “…’The mismatch between the 100 and 400 k.y. components of Pleistocene climate and the relative power of those terms from the eccentricity of the Earth’s orbit remains a challenge to the Milankovitch hypothesis.’…

    The parodox could perhaps be resolved if the charge field/solar wind could be included when ‘paleo-orbital’ calculations are done. Doing this would also reduce the amount of chaos which needs to be found to justify discrepancies seen even in current predictions of planetary orbits.

  31. [...] Comments tallbloke on Cooking the books: snip snip g…Tenuc on Ice ages driven by Earth orien…Tenuc on Ice ages driven by Earth orien…tallbloke on Cooking the books: snip snip [...]

  32. Tim Channon says:

    According to Douglas Adams the trick of flying is aiming at the ground and missing.

    In a simple system, yes attraction would end in collision whereas this is a complex system with phase, delay (same thing), inertia, the whole kit bag. It is also conditionally stable.

    The question which needs accurately answering is whether there is a set of conditions which are stable for a sensible length of time, eventual orbit decay doesn’t matter.

    The paper I linked shows a forbidden region which seems to have an outside envelope which is the odd orbit in question.

    Does it help if I point out that the alien body has mass and therefore will not follow a simple curve? Also don’t forget that an accelerating force toward the earth is concurrent with orbital reposition which demands a reduction in velocity.

    Before invoking new laws it needs proof the old law does not match known properties.

  33. tallbloke says:

    Tim Channon says:
    May 31, 2011 at 4:02 pm (Edit)
    tb:
    “those expected from the Earth’s eccentricity: 95, 125, and 400 k.y”

    http://muller.lbl.gov/papers/geology2.html

    “The mismatch between the 100 and 400 k.y. components of Pleistocene climate and the relative power of those terms from the eccentricity of the Earth’s orbit remains a challenge to the Milankovitch hypothesis.”

    Are we discussing the shift from ice ages every 40Kyears to every 100Kyears?
    If so, is there an extra zero crept in somewhere? Or have I misunderstood? (always possible).

    Two of the Milankovitch cycles are at around 100K years (Eccentricity) and 40 K Years, (axial tilt).

    If those are related to the ice age frequencies, the question becomes one of why one cycle has become dominant over the other.

  34. Anything is possible says:

    tallbloke says:
    June 1, 2011 at 2:13 pm
    Tim Channon says:
    May 31, 2011 at 4:02 pm (Edit)

    “Two of the Milankovitch cycles are at around 100K years (Eccentricity) and 40 K Years, (axial tilt).

    If those are related to the ice age frequencies, the question becomes one of why one cycle has become dominant over the other.”

    TB : I think you would have to factor in the precession cycle to fully answer that one. Its significance varies according to whether eccentricity is high (in which case it becomes very important) or close to zero (in which case precession becomes pretty much irrelevant). The same may also apply according to whether perihelion/aphelion occur at or near the equinoxes/solstices.

    The eccentricity (100Ka) and precession (19-23Ka) cycles are clearly out of phase with one another, but it may be worth investigating whether there is some kind of long-term combined eccentricity/precession cycle (c.2.1m years?) which may help to explain why the relative importance of eccentricity appears to change over the course of time.

  35. tallbloke says:

    AiP,
    good info, and food for thought. I can see why precession (~25k Year) will be important when eccentricity is high. Another factor which might come into play here is ocean heat buffering. The atmosphere cools down pretty much overnight, but the oceans can stay warm for a loooong time. Like millions of years.

    When the precession is such that closest approach during a high eccentricity phase is at sother hemisphere summer, a lot more heat is going to get stored in the oceans. Maybe that tides the Earth through in such a way as the ice age causing cycles skip a beat.

  36. Tenuc says:

    Tim Channon says:
    June 1, 2011 at 12:20 pm
    “…Before invoking new laws it needs proof the old law does not match known properties…”

    Agreed. However in many areas of physics and astronomy the laws have failed, and many empirical patches and ‘fairy dust’ have had to be applied to keep them creaking along.

    The law of gravity has been around a long time, but we now know it ceases to work at galactic distances. This problem has been resolved by MOND (inclusion of an empirical fudge factor to balance the books) or dark energy/matter (a large libation of fairy dust to account for the 95% discrepancy in the mass of the universe).

    Much simpler to give mass and size to photons, and include the E/M field in orbital calculations. Give me simple mechanics over convoluted maths and imagined objects any day.

  37. Tim Channon says:

    More I look the more there seem to be uncertainties. The precession period is not clear, how about 25,800

    On specifically trying to reproduce published results I am not getting a good match.

    Since I have the capability to do exact processing, this is leading to some novel answers.

    I am working with resampled data, been done cleanly. This removes a massive complication and source of major errors, ie. linear processing is now trivial whereas direct processing is impossible, can only be approximation.

    A nice instance was specifically pulling out the circa 100k from a dataset. On period analysis, the best I can do and that is very close to the theoretic limit for that data there is a 100k term. It does not resolve into anything else.

    Giving it to the analyser software, that takes a few seconds to split the term into two (r2=0.99). Computing on those suggests a long term modulation, hence the twin terms. Manual tweaking then suggests a good answer is a single modulated term, add in something else and r2=0.9996. Whether this means anything is moot.

    To make matters difficult, such modulation (in the data) introduces a family of new terms, some of which look likely to be mistaken for part of a different familty. (jigsaw puzzle)

    Given this is derived from Vostak core data there will be confounding other things. Looks like something very circa 500ky as the modulation. This result does kind of match what is supposed to be there but not good enough for numeric compare, eyeball will do.

    I could make an article on this item if showing it would be useful. Fun thing, suddenly occurred to me a side effect of a recent development means it is trivial to cross couple the modulation into a hand defined output and plot that.

    This is why I want accurate numeric simulation data for earth orbitals. then I can phase compare and perhaps untangle some of the data. It is trivial to feed in what is definite and say “now find the correct missing parameters”
    Trouble is that this demands the data timescale is completely accurate: it is suspect.

  38. tallbloke says:

    Tim, it’s clear from the foregoing that I confused your question with the ~40k year to 100K year shift in ice ages phasing. My apologies, I should have read more carefully.

    Please do put something together. As far as I know, the exact length of the precession cycle isn’t well constrained, and the eccentricity cycle evn less so. The field is open for some more cycles analysis, go for it. :)

  39. Doug Cotton says:

    In all this discussion (and elsewhere) I have not seen reference to what must be considerable frictional heat generated (mostly by Sun and moon gravity) when the Earth’s crust is “sucked out” by about 30 cm every revolution in what is called Earth tides. (Of course the atmosphere also has gravity tides which cause warming.) This extra heat would amplify the effect of increased insolation when the sun is closer. I have mentioned this in my site http://earth-climate.com though, to be honest, I’m still endeavouring to quantify the additional effect of gravity from Jupiter and Saturn which appears to be the cause of 60 year and 934 year cycles. These cycles do exist in the temperature records (confirmed by Fourier transforms) and do correlate with angular momentum of the sun and 9 planets (inverted) as here: http://earth-climate.com/planetcycles.jpg and so, i fthey account fully for observed variations in climate, this really debunks the GH theory. What do others think – after reading my site?