Tying celestial mechanics to Earth’s ice ages

From Physics Today

Gradual falls and sharp rises in temperature for millions of years have profoundly affected living conditions on the planet and, consequently, our own evolution.

Mark Maslin is a professor of Earth system science in the department of geography at University College London.

Physics Today 73, 5, 48 (2020); https://doi.org/10.1063/PT.3.4474

Milutin Milanković, a brilliant Serbian mathematician and climatologist, postulated in 1941 that variations in Earth’s orbit could push the planet’s climate in or out of an ice age.1 Vital to that idea is the amount of insolation—incoming solar radiation—at 65° N, a bit south of the Arctic Circle. At that latitude, insolation can vary seasonally by 25%. Milanković argued that reductions in summer insolation allow some winter ice to survive. Each year for thousands of years, ice accumulates around 65° N and eventually forms sheets large enough to trigger an ice age.

Three scientists joined forces 30 years later to verify Milanković’s theory using deep-sea sediment cores collected by the international Ocean Drilling Program. James Hays examined marine microfossils in the cores to estimate past sea-surface temperatures. Nicholas Shackleton measured the oxygen isotope composition in the sediment’s layers, which showed changes in past global ice volume. And the last member of the team, John Imbrie, brought an expertise in time-series analysis to the project. In 1976 they published a seminal paper showing that their climate record contained the same temporal cycles as three parameters, summarized in figure 1, that describe Earth’s orbit: eccentricity, obliquity, and precession.2

Figure
figure 1

Eccentricity describes the shape of Earth’s orbit around the Sun. As Earth experiences a gravitational force from Jupiter, its orbit adjusts during a 96 000-year period from nearly a perfect circle to an ellipse, which causes minor variations in total insolation. Obliquity—the tilt of Earth’s axis of rotation with respect to the plane of its orbit—fluctuates during a period of 41 000 years between 21.8˚ and 24.4˚ and is currently at 23.4˚. A larger obliquity generates a greater difference in the insolation Earth receives during summer and winter.

The third orbital parameter, precession, occurs every 21 700 years and influences Earth’s closest approach to the Sun. During each hemisphere’s summer, precession has the greatest effect in the tropics. Tidal forces of the Sun and Moon, amplified by Earth’s oblate spheroid shape, cause one component of precession. Those forces exert gyroscopic motion on the planet that changes the orientation of its rotational axis. The second component of precession moves Earth’s entire orbit around the Sun in space and resembles the petals of a flower, as shown in figure 1c.

The great ice ages

Over the past 2.5 million years, Earth has undergone some 50 major ice ages and each has substantially changed the planet’s climate.3 During the last one 21 000 years ago, a nearly continuous ice sheet spanned North America. At its thickest, across what is now Hudson Bay, it was more than two miles deep and reached as far south as New York City and Cincinnati, Ohio. The British–Irish ice sheet spread as far south as Norfolk, and the Scandinavian ice sheet extended from Norway to the Ural Mountains in Russia. In the Southern Hemisphere, large ice sheets covered Patagonia, South Africa, southern Australia, and New Zealand. So much water was locked in all those ice sheets that global sea level dropped 120 m, yet if all the Antarctic and Greenland ice melted today, sea level would rise only by 70 m.

How did small wobbles in Earth’s orbit cause those ice ages? Summer temperatures must first decrease a little bit. The consequent accumulation of snow and ice increases Earth’s albedo—the reflection of sunlight to space. Reflecting more sunlight suppresses local temperatures and promotes more snow and ice accumulation, which increases the albedo further. The process, called an ice–albedo feedback, is responsible for building increasingly bigger ice sheets.

Another positive feedback cycle triggers when ice sheets, such as the Laurentide sheet that once covered much of North America, become big enough to deflect atmospheric planetary waves. The change redirects storm paths across the North Atlantic Ocean and prevents the Gulf Stream and its northeastward arm, the North Atlantic Drift, from penetrating as far north as they do today. The surface ocean effects, combined with melt-water increase in the Nordic Seas and the Atlantic, cause a decrease in the sinking of cold, salty water (see Physics Today, April 2019, page 19). As less water in the North Atlantic is driven to the deep ocean, the Gulf Stream pulls less warm water northward, and increased cooling in the Northern Hemisphere expands the ice sheets.

Greenhouse gases (GHGs) in the atmosphere reinforce ice-sheet feedbacks. Analyses of air bubbles trapped in polar ice indicate that during glacial periods carbon dioxide concentrations dropped by a third and methane by half. Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.4

Runaway positive feedbacks froze most of Earth’s water billions of years ago during snowball Earth events, but moisture limitation has prevented a more recent episode. Forming an ice sheet requires a cold, wet climate. But as an ice sheet forces warm surface water farther south, the supply of moisture decreases. By changing the atmosphere and ocean circulation, ice sheets starve themselves of moisture, and that negative feedback loop limits the effects of positive ones.

For the past million years, ice sheets have taken at least 80 000 years to reach their maximum extent, which occurred most recently about 21 000 years ago. However, ice melts much quicker than that: 80% of expanded ice sheets can be lost in 4000 years. Summer sunshine at 65° N triggers deglaciation and starts the melting of Northern Hemisphere ice sheets. Rising concentrations of carbon dioxide and methane in the atmosphere promote climate change and further melt large continental ice sheets. Such processes work against the ice–albedo effect, which acts to keep the ice sheets intact by producing a cooler microclimate.

Ultimately, rising sea levels diminish large ice sheets because the coldest that seawater can be is −1.8 ˚C, whereas the temperature of the ice sheet’s base is −30 ˚C. As seawater melts the ice sheets by undercutting them, ice calves into the ocean. The calving raises sea level further and causes more undercutting (see Physics Today, October 2019, page 14). The sea-level feedback mechanism can be extremely rapid. Once the ice sheets are retreating, the other feedback mechanisms—albedo, atmospheric and ocean circulation, and GHGs—are reversed. That’s why glaciologists and climatologists worry about future climate change: It will activate those feedbacks and cause irreversible instability to the Greenland and West Antarctic ice sheets (see Physics Today, July 2014, page 10).

The eccentricity myth

The last million years of glacial–interglacial cycles, each lasting about 100 000 years, have a saw-toothed pattern with a long period of cooling followed by a short, warm one of rapid melting. More than a million years ago, the cycles were smoother, and each lasted only 41 000 years, as shown in figure 2. That period corresponds to the length of the orbital change associated with obliquity, which controls the heat transfer between low and high latitudes and thus regulates ice growth.

Figure
figure 2

Figure 2. Many glacial–interglacial cycles (red solid line) during the last 5 million years can be seen from measurements of the oxygen isotope composition of lake records. Large ice sheets started to grow in North America 2.5 million years ago during the intensification of Northern Hemisphere glaciation (iNHG). The development of the atmospheric Walker Circulation (DWC) started 1.7 million years ago in the Pacific Ocean and is sustained by a large east-to-west sea-surface-temperature gradient. About 1 million years ago, during the Mid-Pleistocene Revolution (MPR), the polar ice caps expanded toward the equator, and the glacial–interglacial cycle period increased from an average of 41 000 years to 100 000 years. (Adapted from ref. 3.)

For many years, scientists struggled to explain the 100 000-year glacial–interglacial cycles because the 96 000-year eccentricity mechanism has a similar length. But eccentricity is by far the weakest of the orbital variations, and many thought it predominantly modulated precession, so scientists suggested several nonlinear feedbacks to explain the discrepancy. But they found an answer when they realized that the 100 000-year cycle is a statistical artifact.

The average length of the last eight cycles is indeed 100 000 years, but each one varies from 80 000 to 120 000 years. Every fourth or fifth precessional cycle is weak enough that ice sheets can grow bigger and thus more vulnerable to sea-level rise during deglaciation. The next precessional cycle is always much stronger than the previous one and initiates rapid, extreme deglaciation through the sea-level feedback.5 Although the timing of deglaciation seems to better match precession, some researchers have argued that the long glacial–interglacial cycles may correspond to every second or third obliquity cycle.6

Full article here.

HT/Leif Svalgaard

160 thoughts on “Tying celestial mechanics to Earth’s ice ages

  1. Greenhouse gases (GHGs) in the atmosphere reinforce ice-sheet feedbacks. Analyses of air bubbles trapped in polar ice indicate that during glacial periods carbon dioxide concentrations dropped by a third and methane by half. Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.

    Unfortunately, they go this wrong. They say that “during glacial periods carbon dioxide concentrations dropped by a third and methane by half”. Clearly the glaciations were driving that variation of GHGs.
    Other than that, their article does a good job laying out the various causes and feedbacks.

    • Wonderful catch. They will, undoubtedly, be able to come up with an excuse for why they’re not really wrong. That’s what experts do.

      Oh, what a tangled web we weave
      When first we practice to deceive! Sir Walter Scot

      If you can pin them down, like in a court of law for instance, they will trip themselves up.

      • > That’s what experts do.

        But does Mark Maslin actually have any expertise outside the business world, where his fingers are permanently in a plurality of pies profit[eer]ing off the klimate koncerned and their koncern?

        The poorly-named online soliloquism platform The Conversation offers a great way to follow Maslin’s adventures in moneymaking: compare his Disclosure Statements from week to week.

        One day he’ll write:

        Disclosure statement
        Mark Maslin is a Founding Director of Rezatec Ltd, Director of The London NERC Doctoral Training Partnership and a member of Cheltenham Science Festival Advisory Committee. He is an unpaid member of the Sopra-Steria CSR Board. He has received grant funding in the past from the NERC, EPSRC, ESRC, Royal Society, DIFD, DECC, FCO, Innovate UK, Carbon Trust, UK Space Agency, European Space Agency, Wellcome Trust, Leverhulme Trust and British Council. He has received research funding in the past from The Lancet, Laithwaites, Seventh Generation, Channel 4, JLT Re, WWF, Hermes, CAFOD and Royal Institute of Chartered Surveyors.

        Then:

        Disclosure statement
        Mark Maslin does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

        Then:

        Disclosure statement
        Mark Maslin is a Professor at University College London, a Royal Society Industrial Fellow, Executive Director of Rezatec Ltd, Director of The London NERC Doctoral Training Partnership, and a member of Cheltenham Science Festival Advisory Committee. He has received funding in the past from the Natural Environment Research Council, the Royal Society, DIFD, FCO, Innovate UK, Carbon Trust, UK Space Agency, European Space Agency, Leverhulme Trust, WWF, RICS, British Council, and CAFOD.

        In one ‘conversation,’ I felt commenters were being a bit unkind to the (absent) author of the post, so I wrote:

        > Guys, please be patient with Mark. Wouldn’t YOU have turned every idea you touched into incoherent wibble too, if YOU had to bear a cross like this:

        [paste a Disclosure Statement at random from Maslin’s back catalogue]

        > After all, wasn’t it Upton Sinclair and Al Gore who said it’s hard to get a man to understand something when his salary depends on his not understanding it? Salaries don’t come much bigger than Maslin’s.

        • The author of this paper wrote: “Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.”
          Huge error!

          I’m guess the author is mystified when his beer goes flat as it warms up. Drink up laddie – you sound so much more intelligent when you’re dead drunk.

          From 2012:
          https://wattsupwiththat.com/2012/08/30/north-american-energy-independence-by-2020/#comment-889468

          (Plant) Food for Thought:

          One reasonable scenario for the end of life on Earth is insufficient atmospheric CO2 to support photosynthesis, as CO2 is permanently sequestered in carbonate rocks, hydrocarbons, coals, etc.

          Since life on Earth could actually end due to CO2 starvation, should we be paying energy companies to burn fossil fuels to increase atmospheric CO2, instead of fining them due to the false belief that CO2 from fossil fuel combustion causes catastrophic global warming?

          Could T.S. Eliot have been thinking about CO2 starvation when he wrote:
          “This is the way the world ends
          Not with a bang but a whimper.”

          Regards, Allan 🙂
          ______________________________

          The Holocene is the current geological epoch. It began approximately 11,650 years before present, after the last glacial period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period.

          Now, global warming fraudsters have proposed a new epoch since man started burning fossil fuels that requires a new name – they suggest the “Anthropocene”

          Back in 2016, I suggested that we name the new epoch after these warmist fraudsters and their devoted minions – I proposed the AssHolocene.
          https://wattsupwiththat.com/2016/01/30/saturday-satire-welcome-to-the-new-era-of-climate/#comment-1702667

          • “The author of this paper wrote: “Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.”
            Huge error! ”

            Absolutely. This isn’t just wrong, it’s an outright lie.
            It looked like an interesting article, but when I read that I gave up.

            Before I stopped buying New Scientist, they did actually agree that temperature changes preceded CO2 changes, though of course they tried to spin it into something bad.

            As the writer added “, not a response to it.” he was clearly aware what the data shows.
            Chris

          • Chris Wright – May 3, 2020 at 3:05 am

            Absolutely. This isn’t just wrong, it’s an outright lie.
            It looked like an interesting article, but when I read that I gave up.

            I gave up also …… because I thought the entire paragraph was FUBAR, ….. to wit:

            Greenhouse gases (GHGs) in the atmosphere reinforce ice-sheet feedbacks. Analyses of air bubbles trapped in polar ice indicate that during glacial periods carbon dioxide concentrations dropped by a third and methane by half. Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.

            Just how does the good professor figure that ….. “Greenhouse gases (GHGs) in the atmosphere reinforce ice-sheet feedbacks”?

          • “Before I stopped buying New Scientist …”” I must confess that I only gave up about 2 years ago. Since then I haven’t even touched a page. I now no longer get mad (in the American sense) when I read. Looking back I can’t believe it took me so long although I did enjoy it to start with but that was over 30 years ago. Eventually I realised it wasn’t ever going to get any better, it was only going to get worse.

          • I managed to move past that one, but then I came to this:

            “as an ice sheet forces warm surface water farther south”

            Whut?

      • My expert at logical thinking, E. T. Jaynes (author of Probability Theory: The Logic of Science) says eschew ad-hockery. Develop your argument, make your assertion, and STFU. Ad-hockery is #FakeNews click-bait.

    • Everything else I’ve read in the past half dozen years says that paleo evidence shows that GHG changes lag temperature changes (by a rather large measure), not precedes them. Either this article, or many others in opposition, are incorrect. Does this difference of view exist because of some real uncertainty in the physical evidence or is it simply a matter of faith and ideology?

      • I agree, and stopped reading at Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.4 That has not been true for the last several glaciations in this ice age. Also the author calls the present glaciation an ‘ice age’, when the present ice age began 2.6 Ma and is the Quaternary Glaciation.

          • Then they need to find a different faux pas. The one identified is at the heart of the biggest fraud in human history.

          • Well here’s another faux pas: I have heard several numbers for the precession cycle but they cluster at 26,500 years, not 21,700. Where did that come from?

            This dubious description claims it is 23,000 years.
            https://earthhow.com/milankovitch-cycle/

            There is no discussion of the fact that the North Pole was probably not at its present location during the last ice age. Maybe it was somewhere in Baffin Island…or? Maybe that is why the Laurentian ice sheet was placed so lopsidedly on the Earth.

            If the temperature of the globe is so related to the concentration of CO2 and methane, why was it so much warmer thousands of years ago when CO2 was low and there were large trees growing well north of the present tree line in Canada (which has been moving north for some time, meaning it was colder more recently). How can all that permafrost be melting to release all that methane from all that stored biomass, unless it grew there in the first place? Ergo, it was much warmer before it froze to become permafrost packed with frozen trees.

            How do orbital mechanics or CO2 or methane explain all that? They don’t. Something else is going on.

          • Agree with Leif, you shouldn’t stop reading, you should check the citation which refers only to the most recent de-glaciation and says nothing about what ‘always’ happens – and is also largely dependent on modelled data…

          • Crispín,

            The climatic effect of precession cycles results from combining axial and apsidal precession.

      • The only analysis of which I am aware ( but wouldn’t be surprised if it remains the only peer-reviewed analysis) is “The phase relations among atmospheric CO2 content, temperature and global ice volume over the past 420 ka” by Manfred Mudelsee in Quaternary Science Reviews 20 (2001) 583-589. Yes, Dr. Mudelsee shows that changes in CO2 lag proportionate changes in temperature, overall, by about 1000 years.

        Unfortunately, Professor Maslin does not declare which of the two possible explanations provides the basis of his “science”, i.e.:
        1. CO2 time-travels to the past to control the temperature that prevailed 1000 years previously, or
        2. temperature is prescient, and adjusts to obey CO2 levels that it can foresee 1000 years in the future.

        • Clearly #1 and as time to the past would cause insurmountable causality problems. That’s why CO2 is the MagicMolecule™️. It can do anything that fraudsters like Maslin want it to. No law of nature is too burdensome for the MagicMolecule™️.

      • The comment about changes in GHGs preceding temperature changes is clearly wrong. Many comments here addressed that. It’s been validated by data hundreds of times. I suggest that the author knows that he’s wrong, i.e. he deliberately left an incorrect statement in his paper. Why? Look again at the list of associations and other sponsors that have funded him. He is not going to burn any funding bridges by stating an unacceptable truth. It’s the obligatory gratuitous statement that the funders want to see, need to see, because it signals that the author, no matter what his findings may show, is on the “right” side of the debate. So they can continue to pay him, because in the end, he’s one of them.

        Ice sheet buildup only occurs after thousands of years of declining temperatures, which chill the oceans. Colder water absorbs and holds more dissolved gases than does warmer water. Both the reduced concentration of “greenhouse” gasses, and the buildup of ice sheets, lag the cooling of the atmosphere and oceans. The lag time for ice sheet accumulation is much longer than the lag time for increased gas absorption. So by the time the permanent ice sheets are forming, the reduction in atmospheric GHGs (due to colder oceans) has already been well underway, probably for thousands (or even tens of thousands) of years. Thus while a reduction in atmospheric GHGs likely does precede ICE SHEET formation, the GHG reduction is still caused by colder temperatures. The only air bubbles being analyzed are those trapped within the ice, which were formed late in the cooling process.

    • Leif Svalgaard
      May 2, 2020 at 2:13 pm

      I totally agree.

      However, what do you think is the mechanism…is it cooling oceans pulling CO2 and or CH4 from the atmosphere or something else?

      Does this mechanism also explain the increasing CO2 from Mauna Loa as we emergee from the Little Ice Age or is it mostly manmade CO2 and if so, any idea how much is natural vs. manmade?

      • Does the Mauna Loa data reflect the world-wide drop in economic activity?
        That comparison ought to illuminate how much CO2 comes from human activity.

    • I have always wondered if atmospheric pressure would change with less GHGs (CO2 H2O CH4) and world’s oceans being 120 meters lower. Would it have made the South and North pole, where the atmosphere is a lot thinner even colder?

    • Most amusingly, they then contradict this GHG claim two paragraphs later, by stating that it is a positive feedback to the initial trigger of more sunshine.

      “Summer sunshine at 65° N triggers deglaciation and starts the melting of Northern Hemisphere ice sheets. Rising concentrations of carbon dioxide and methane in the atmosphere promote climate change and further melt large continental ice sheets.”

      Considering the article is focusing on the role of insolation as the primary driver of ice ages, the earlier sentence doesn’t make sense and is not supported by the ice core data.

    • Ha ha, that sentence was like cycling my bicycle into a brick wall. I was happily enjoying the article until I arrived at that statement and I immediately jumped to the comments section. But, Leif, I will take your advice and finish reading. Only you advise it, I wouldn’t.

    • Why do they mention only CO2 and CH4 as GHGs when the most powerful, by far, GHG is H2O? Is it not obvious that increasing temperatures cause increasing atmospheric H2O, while increasing ice cover reduces the GHG H2O?

      • How on earth – or in the atmosphere, could CO2 cause warming at the bottom of a glaciation, when CO2 was at its lowest of 180. Where did the extra CO2 come from to start the warming?

    • Getting that wrong and still “doing a good job” is like asking Mrs Lincoln if she enjoyed the play.

    • He got the idea from Scottish scientist James Croll, FRS, (2 January 1821 to 15 December 1890) .

    • Wasn’t 21,000 years ago a glaciation period, not an “ice age”? We are currently in the Quaternary Ice Age, which has so far encompassed many glaciation and interglacial periods.

      • “Ice age” doesn’t have a specific meaning in geology, so can be used in various ways.

  2. Clearly, CO2 increase follows warm up into glacial termination, which begins with CO2 at its lowest, as during the depths of the last glacial maximum.

    I’m of the tilt cycle school. The apparent average ~100,000-year glaciation cycle seems to result from two or three 41,000-year obliquity cycles. Before the Mid-Pleistocene Transition, “ice ages” lasted ~41,000 years; after it, ~82 to 123 thousand years. As the Pleistocene progressed, the baseline condition got colder, so that every other or every third nascent interglacial was stillborn. Instead they should up as interstadials within a longer glacial interval.

    The present Holocene is just another interglacial, not an epoch unto itself. It has been cooler than the last one, the Eemian.

    • A lot of geologists, paleontologists, and archaeologists agree with the idea that we are not out of the Pleistocene. One piece in disturbing evidence in the available data is that over the last 800,000 years or so, the swings between glacial epoch and interstadials have intensified dramatically. At the same time the maximum temperatures of the interstadials have declined. The system of climate looks to be increasingly unstable. If you look at delta-O18 data over the Pliocene and Pleistocene the planet has been cooling very steadily – in fact, with a couple of short term, dramatic reversals the entire planet has been cooling since the mid-Mesozoic. Climate swings are regular over much of that span with lower amplitude, “higher” frequency swings (40,000 years spans as opposed to 80,000-100,000 spans). With the Pleistocene the amplitude of swings doubles or triples (at least), frequency is considerably lowered and the peak temperature is lower.

      CO2 , methane and water vapor do not account for any discernible fraction of those changes. Human effects are very recent and are yet to be separated from background noise.

      • As long as continental plates and, therefore, oceanic currents stay as they are, we won’t be going out of this ice age anytime soon. Ice age in the northern hemisphere started 2.8 million years ago when the Panama strait formed.

  3. “Changes in GHGs always precede variations in global temperatures”

    That’s the opposite of what I’ve always read.

    • True, and why is there no mention of water vapor, the most influential GHG? Only mention of atmospheric gas is CO2 and methane? Yet it is the water vapor that forms those prominent ice sheets, and the less heating of the atmosphere, the less water vapor it holds, thus even colder.

      • CAGW is the last of the great monotheistic religions. CO2 is the one true god, but his archangel CH4 shares the burden of bestowing His radiative heat transfer upon the just and the unjust* alike.

        Water vapour is a false god, a graven image worshiped by the savage and the heathen and the unjust and the unclean and the fornicator.

        * – And Satan doth urge the unjust to gather together with the savage** and the heathen and the unclean and the fornicator to carry gooey black stuff from the pits of the earth so that they may burn it in a fiery furnace that maketh their chariots go forth upon the land and upon the sea and upon the air, and that maketh of their cities a place of comfort and ease, and mutiplieth the fruits of their fields and their groves so that they know nothing of hunger. Then His wrath knoweth no bounds, and He redoubleth His radiative heat transfer and He maketh the trees of the forest to burn, and He maketh the ice of the cold places to melt, and He maketh the seas to rise up on the very land, yea, even on to their cities. And there will be great wailing and gnashing of teeth (Epistles of St. Michael 19:98)

        ** of whom it is written “By his orange hair shall ye know him”

    • they’re full of it…
      there’s nothing that would made CO2 start to increase before temperature…and nothing that will make it continue to increase but temperature

  4. > “During the last one 21 000 years ago, a nearly continuous ice sheet spanned North America.”

    “…spanned the Northern portion of North America.”

    • Dr. Maslin probably meant from the Pacific to Atlantic Oceans rather than from the Arctic Ocean to Isthmus of Panama.

      • I know and wasn’t personally triggered but the warmists are so picky I wanted to clarify. I misspent my youth scrambling over those very same glacial boulders left behind in the US Northeast.

        Want to know how far the glaciers pushed? It is called Long Island.

  5. if you just surimpose the 41’000 and 100’000 years cycles , then you can understand why the previous interglacial period ( Eemian 125’000 years ago ) was warmer than current period ! That’s a mathematical explanation . CO2 concentration varied from 180 to 280 ppm between -20’000 and -10’000 years , so it changed about only 1 ppm per century ! how can someone imagine it could have an impact on the climate ! that’s a joke ! During Holocene , the CO2 concentration increased from 275 to 280 ppm while the temperature decreased !
    Facts completely disagree the climate alarmists and models !

  6. I had not read of the two feedback processes that cause and then end ice ages. Interesting. However, the precession of perihelion is the result of gravitational perturbation by other planets on Earth’s orbit; precession of the equinox is due the gravitational torque of the sun/moon on the Earth’s equatorial bulge. They are thus separate phenomena, one having a period of roughly 26,000 years and the other about 112,000 years. The interplay of the two results in the Earth’s perihelion returning to the same perfect calendar date variably between 20,700 and 28,000 years.

    At the present time computed solar insolation from one vernal equinox to the next is increasing. Is this, then, a mechanism for slowly increasing planetary warmth?

  7. ” That’s why glaciologists and climatologists worry about future climate change: It will activate those feedbacks and cause irreversible instability to the Greenland and West Antarctic ice sheets”

    But if those changes did not “cause irreversible instability to the Greenland and West Antarctic ice sheets” in the past, why do that assume they will in the future?

  8. There can be no doubt that orbital mechanics is the primary driver that temporarily pushes out of ice ages. However;

    “Runaway positive feedbacks froze most of Earth’s water ”

    NO! NO! NO! Temperature dependent changes to the system are more properly represented with temperature coefficients, not feedback. The concept of feedback is independent from state dependent attributes of the system, for example, the surface reflectivity or GHG concntrations.

    The only reasons the Earth would freeze is if the orbit took it too far away from the Sun or if the Sun got too weak. Ice simply can not exist in the oceans between the tropics under current orbital and solar conditions. Even with reflection, there’s enough solar energy to melt any ice and keep the surface warm enough to prevent ice from returning even if there was no CO2 in the atmosphere.

    The application of Bode’s linear feedback amplifier analysis is what predicts the runaway condition, but this requires the implicit source of Joules powering the gain. This is one of Bode’s preconditions for using his amplifier analysis along with strict linearity of the amplifier. This means that if the input is 1 and the output is V, the output will be the input times V for all possible inputs.

    The W/m^2 input and the temperature output of the climate feedback amplifier are not linearly related to each other. Approximate linearity around the mean is insufficient to satisfy Bode’s precondition and there’s no wiggle room to get around this. Considering the average not accounted by the incremental analysis is the implicit power supply is not correct either as this assumes non linearity! Two wrongs don’t make a right.

  9. OK, I’m a layman and I come to this website to learn. Can someone help me to understand something. The main article says,

    “As seawater melts the ice sheets by undercutting them, ice calves into the ocean. The calving raises sea level further and causes more undercutting (see Physics Today, October 2019, page 14).”

    The link to Physics Today includes the statements,

    “The glaciers melt more quickly than usual if winds diverted eastward by human activity drive warmer circumpolar water onto the continental shelf and underneath the floating ice.”

    Q.1 How can human activity change the direction of the wind ?

    Q.2 Can the wind blow water underneath floating ice ?

    Q.3 How does the melting of floating ice raise sea level ?

    • Furthermore, article says “Every fourth or fifth precessional cycle is weak enough that ice sheets can grow bigger and thus more vulnerable to sea-level rise during deglaciation. The next precessional cycle is always much stronger than the previous one and initiates rapid, extreme deglaciation through the sea-level feedback.”
      This seems to mean the more the ice sheets extend onto the now-dry continental shelves, the faster they melt back. But, the sea has retreated because so much of it has become frozen into the ice sheets. The freezing took place in the continental interiors, and then the perimeters of the ice sheets extruded out onto the exposed shelf.
      The seas can’t rise until ice starts melting, and melting starts at the lowest elevation – the continental shelf. The rising seas will not meet the ice sheet because the sheet already melted back from low elevations.
      SR

      • Addendum:
        Most of the Larentium ice sheet expanded southward into what is now central U.S., without reaching the Gulf of Mexico. Melt back had nothing to do with rising seas.
        Also, much of Norway, Patagonia and New Zealand do not have continental shelves. Where was undercutting of seawater melting continental ice sheets supposed to have happened? Only on eastern seaboard of Canada , and in the North Sea?
        SR

        • The Atlantic shore of Patagonia has a vast shelf extending to the Falklands. The Pacific side is abrupt but does have the sunken valley south of Puerto Montt.

          New Zealand is surrounded by shelf, being a micro continent, or as was argued in 2017, a sunken continent.

          How much of these shelves is exposed when sea level falss by up to 140 meters during ice sheet and glacier advance is subject to study.

    • David Lilley May 2, 2020 at 3:23 pm
      “As seawater melts the ice sheets by undercutting them …blah …blah …blah

      That’s the quote I copied out too. You have to believe that warm water sinks under the surface water, and then flows under the sea ice, under the shelf ice and melts the glaciers at the grounding line.

      • Not sure whether it makes much difference in this case, but “warm” water does sink… It’s why ponds rarely freeze solid. Water (liquid) is at its greatest density around 4C. Once the pond gets really cold, the coldest water stays at the top, just under the ice sheet, and helping to form an insulating blanket that prevents (or at least greatly slows) the freezing of the water below. Heat transfer in the pond by convection comes to a screeching halt.

        Water is a magical chemical, and without its unique properties there would be no life on earth.

    • In reference to your Q3, I expect the rise in Sea level is due to the land based ice sheets. Antarctica and Greenland for example. Floating ice should not be expected to contribute to a sea level increase.
      I do not have any answer to your other questions.

    • “How does the melting of floating ice raise sea level ?”
      Exactly my question also. Last time the ice cubes in my drink melted, the glass did not overflow

  10. Stopped reading when dopey author claims erroneously that GHG’s cause climate change….we all know here that the Vostock ice core samples unambiguously show temp shifts always precedes a change in CO2 levels…and common sense should get you the rest of the way.
    How is it that someone bright enough to pass the various tests they pass to become a scientist cant follow simple logic when presented with the challenge of thinking for yourself? Sad.

      • And, there’s no grant money if one doesn’t toe the line of the current paradigm and sing praises to the god Gaia.

        • Years ago, at the Cheltenham Science Festival, I put that point to Prof Maslin, one to one, after his lecture. He claimed that he would follow the scientific evidence, even if it meant falling out of line with the conventional view. I observed that I would watch closely to see if that ever happened…So far, I think not!

        • I spoke to Professor Maslin after his talk at the Cheltenham Science Festival some years ago, and asked him whether he would be prepared to publish results if they went against the conventional orthodoxy on climate change. He claimed he would, despite the chance of being ostracised. I said I would observe closely to see if that happened, and to date it has not…

    • Simple. Future grants. This was walking through a mine-field. It is game over if they acknowledge that “Changes in global temperatures always precede variations in GHG’s.” The elephant-in-the-room lie is quite a part of climatism, as much so as integrity is not.

  11. ” Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it. 4″ I searched down the reference https://www.nature.com/articles/nature10915
    I come up with: “The role and relative importance of CO2 in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show that temperature is correlated with and generally lags CO2 ”
    “and generally lags CO2”
    BS alert….. So for “unclear and generally” we get CO2 is the cause: When do we start shaming these people for spouting fairy tales instead of using science ?

  12. The claim that increases in GHGs always precede warming is enough for me to dismiss the whole thing as untrustworthy.

    What sort of illogical (or dishonest) thinker can posit such a ridiculous hypothesis? We are supposed to believe that it is not warming causing more outgassing in sync with Milankovic cycles, but some miraculous increase in GHGs that precedes and causes warming but just coincidentally always in sync with Milankovic cycles? Absolutely absurd!

    Nobody can be that obtuse, so it can only point to corruption.

      • In Christian theology, faith requires not only no evidence, but belief in the absurd. Without blind faith, contrary to all actual experience of Earth, of what value can faith be? If the resurrection be normal, with people coming back from the dead after three days a common occurrence, then why rely upon faith rather than observation, experience and evidence?

        • In the spiritual realm of the afterlife there can be no evidence, only faith.. However down here in the realm of the living as a Christian evidence is as important to me as it is to anyone else. The bible says: “Thou shalt not bear false witness.” I have no faith in any who do bear false witness. So I have no faith in an otherwise intelligent man who tells me that in the past an increase in CO2 in the atmosphere gave rise to an increase in global temperature.

      • As Church Father Tertullian famously wrote, “I believe because it is absurd”.

        As Martin Luther, founder of Protestantism wrote, with characteristic circumspection, “In order to be a Christian, one must tear the eyes out of your reason”.

          • It’s a paraphrase of Tertullian’s “Prorsus credibile est, quia ineptum est”, which means, “It is certain because it is absurd”.

            Close enough for exegesis work.

          • Unless you find resurrection after three days dead to be an everyday occurrence.

          • Yes, it is a paraphrase, by Physician and polymath Thomas Brown in Religio Medici (1643).

  13. This post, and the vast majority of other comment on this topic, continues to miss the fact that eccentricity is the only one of the orbital parameters which changes the total annual solar energy incident at the earth’s surface.

    Obliquity and precession most obviously do not: they simply effect where on the earth and at which time insolation occurs.

    Eccentricity does, because the semi-major axis of the Earth’s orbit is constant, IIRC because its total angular momentum is constant. Therefore high eccentricity corresponds to shrinkage of the semi-minor axis, and higher annual insolation because the planet is on average closer to the sun.

    From memory, total annual energy input (at constant sun) goes like 1/SQRT(1-e^2). Plot it against the Antarctic ice core temperatures, you will see the pattern.

    • Timing and duration of insolation are important, Russell. If ice builds up longer during winter, and is no longer fully melted in summer, much more of the summer insolation is reflected to space by the higher albedo of the ice.

    • I really tire of the constant assertion that orbital eccentricity “causes minor variations in total insolation” [emphasis added]. The Earth’s current orbital eccentricity of 0.0167 results in a change of 6.46% in total insolation from perihelion to aphelion. That change occurs every 182.5 days. It dwarfs every other variation in energy transfer to and from earth by a factor of at least 25. It is the single largest variable in the entire Earth-Sun-space energy balance, and its magnitude is known. We debate whether there is a 2.3 or 3.4 W/m^2 shift in the Earth’s radiative energy balance due to CO2 in the atmosphere, and ignore the fact that the actual top of the atmosphere insolation changes by 88 W/m^2 every 182.5 days.

      Don’t you people notice this? To quote Mugatu, sometimes “I think I’m taking crazy pills.”

      • Right! What counts is not total insolation but hemispherical insolation. There has rarely been less North/South symmetry than in the Pleistocene. –AGF

      • Michael, wouldn’t the time period be 91.25 days? The cycle goes from perihelion to aphelion AND BACK every 182.5 days. Not sure what if any difference that makes , I agree with the rest of your comment.

    • Oops! A highly eccentric orbit (a comet) spends little time close to the sun. Whatever the magnitude, an increase in eccentricity would likely result in an increase in velocity at perihelion, not so?

  14. I have another question to aid my education.

    My understanding is that when ocean water evaporates, the O18 content of the H2O vapor is influenced by the local temperature. The vapor rises, condenses into clouds, blows somewhere else, and (some) falls as snow over Greenland or Antarctica. So, when ice cores are analysed for their O18 content, surely this is a proxy for the temperature at the ocean / atmosphere boundary where the water evaporated. Why do studies treat it as a proxy for local temperatures in Greenland or Antarctica where the snow fell ? If I am wrong, then why ? If I am right then these proxy temperature variations do not need to be adjusted for polar amplification.

    Can anyone comment please ? Thanks for any help.

    • I can’t help but only confuse you more. Surely the mechanism suggests that the drop in incoming radiation at the tropics is more than compensated by the heat not shared with the polar latitudes.

    • More confusion: It has always seemed to me that most of the O18 depletion takes place when water freezes. The O16 goes with the ice and the O18 stays behind. When the ice melts rapidly as at the end of an ice age, the O18 depleted meltwater blankets the North Atlantic, then is further depleted when it evaporates and snows out on Greenland, leaving the scientists thoroughly confused, thinking this period, known as the “Younger Dryas,” was a period of cooling instead of rapid warming at the end of an ice age.

      • On the windward side of a mountain, the δ18O and δD values of precipitation decrease with increasing altitude. Typical gradients are -0.15 to -0.5 ‰ per 100m for 18O, and -1.5 to -4 ‰ per 100m for D.

        http://snobear.colorado.edu/Daniel/isotopes/oxygen18.html

        What is it a proxy of in ice cores in the centre of permanent ice sheets? Precipitation? Mostly snow but different snow? Heavier rainfall in the subtropics so that the remaining water vapour moving towards the poles is lighter (lower average molar mass)?

        • Makes sense since the O16 molecules are more easily incorporated into the ice crystals so are precipitated first at lower altitudes.

      • They typically invert the O18/T graphs for easy correlation. It’s the heavier, slower moving water molecules (with 18O) that are preferentially precipitated as ice. As the ice caps build up the ocean becomes 18O depleted, which must be taken into account in the T modeling. –AGF

    • For what it’s worth, Kim, it seems like you’re trying to say something

      What it is ain’t exactly clear.

          • Telling me I got to beware…

            There’s battle lines being drawn
            Nobody’s right if everybody’s wrong
            🙂

          • Actually Kim, I think you were right with the typo. Mann is on a GIG, he is just not very good at Gigging….

          • Heh.
            I’ve been amazed how frequently a typo or a slip has improved what I’ve tried to say.
            I saw that but still needed the CO2 creeping into the hearts and minds.
            ==========

  15. Rapid polar melting is clearly not a welcome scenario, however rapid sub-polar freezing would be far worse and is far more likely. The latter is harder to talk about though, as it lacks the former’s scope for immediacy and emotive language. While children can be frightened by the bogeyman of runaway warming tomorrow, due to the actions of evil old white men, runaway freezing coming at a less exact date due to the actions of our solar system lacks the disaster-movie plotline needed to gain the attention of vulnerable young minds.

  16. Thinking about how close we could be to the next major glaciation always makes me marvel at how mind-numbingly absurd it is that power elites are preparing for the exact opposite of the inevitable climate catastrophe.

    If the earth warms a further 2-4 degrees and it’s because of our actions, that would be just what we would recognize as a major success in avoiding the next killing ice age.

    Of course I don’t accept that we have that power and also doubt that this largely natural warming is going to last. What we’re seeing is one of the last and coolest of the periodic warming periods of the Holocene.

    When it ends, that may be the mother of all crises. Famine and war as we have never experienced. It may be centuries or a millennium or two off, but in a geologic blink of the eye, it’s coming. And then at least 410 centuries in the deep freeze, much longer than recorded human history, maybe even a thousand centuries!

    We won’t be there, but it would be ironic to see the eyesore windmills plowed down and pushed into the sea by the advancing ice sheets. That would at least be a small consolation.

    • Hi, Rich.

      You might factor in a forecast of the amount of human-produced waste heat from all the electricity we will be using as this cooling approaches, heat which was not being terrestrially produced at the onset of the last glaciation.

      The signs to be watching for? How about here and there advancement of glaciers over a few decades, cooling summer nights, earlier NH winter onsets, and (gasp) incomplete Spring/Summer melt of snowfall in far north of the Canadian Archipelago. After all, the glaciation starts with multi-year accumulation of snow. Lets watch for that…

    • Yep. Our ‘leaders’ have it backasswards. Glaciation is inevitable within the next few thousand years. I doubt we can stop it but extra CO2 has to be beneficial.

  17. Ice Core Data Debunk CO2 Global Warming Concerns

    The NOAA Climate.gov website provides “science & information for a climate-smart nation”. A February 20, 2020 post “Climate Change: Atmospheric Carbon Dioxide” included the concern :

    The global average atmospheric carbon dioxide in 2018 was 407.4 parts per million (ppm for short), with a range of uncertainty of plus or minus 0.1 ppm. Carbon dioxide levels today are higher than at any point in at least the past 800,000 years.

    They post summarized the concern with the following highlights:

    · Human activities have increased the natural concentration of carbon dioxide in our atmosphere, amplifying Earth’s natural greenhouse effect.

    · The global average amount of carbon dioxide hit a new record high in 2018: 407.4 parts per million.

    · The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago.

    The post included a chart showing “ ice CO2 during ice ages and warm periods for the past 800,000 years” supporting their concerns. What they didn’t show was corresponding global temperatures. That all five of the interglacial periods in the 450,000 years included in the Vostek ice cores had peak temperatures similar to current levels despite the lower CO2 levels. The Eemian period some 130,000 years ago were 4 deg C higher than current levels with 290 ppm CO2 levels.

    Clearly CO2 levels were not determinative of global temperatures during the four previous interglacial periods. What’s different is global temperatures during the four periods quickly started downward. However the current Holocene warming has lasted several thousand years. The current high CO2 levels reflect the duration of the warming period not the level of fossil emissions.

    The increased CO2 levels reflect the increased length of time during which increased global temperatures have increased CO2 out gassing from ocean. That increased global temperatures are the reason for higher CO2 levels not the result.

    Fossil CO2 emissions have absolutely nothing to do with the current temperature level. That Al Gore’s “inconvenient truth” was a lie.

    • There seems to be a significant amount of evidence that (overall) cooling has been going on for the past 3000 to 3500 years, with corresponding increases in the Greenland ice sheet, or at least that has been reported from a number of studies discussed on WUWT and various other places.

      If this is so then, according to your statements, the CO2 atmospheric concentration should have downward pressures. Is there alternate evidence that says temperatures have been increasing since the Holocene optimum rather than decreasing?

      • The East Antarctic Ice Sheet, repository of most of the freshwater on Warth, quite retreating ove 3000 years ago, after the Holocene Climatic Optimum and Egyptian and Minoan Warm Periods.

  18. The authors of the paper ignore the fact that recent analysis has shown the both hemispheres are cooling and warming in synchronism which is a paradox for M’s theory.

    Pushing dead theories is ‘sciency’ twiddling of the thumbs. It really does nothing.

    The summer insolation at 65N theory cannot explain that as the two hemispheres are out of phase in terms of summer insolation,

    Milankovitch theory that changes in summer solar insolation at 65N caused, the glacial/interglacial cycle, is a dead theory, not part of the solution.

    There are more than at least a dozen paradoxes (observations that cannot be explained by Milankovitch’s theory.) More importantly there are sufficient observations to determine what does cause the cyclic abrupt climate changes.

    The following is a partial list of some of the problems with the theory.

    1) The observational effects of that are found in the paleo record is physically impossible for changes in solar insolation at 65N to explain.

    The effect in the climate record is an order of magnitude too high and there is evidence of abrupt change, both hemispheres (same periodicity) not gradual change.

    https://news.wisc.edu/glacial-records-depict-ice-age-climate-in-synch-worldwide/

    Glacial records depict ice age climate in synch worldwide

    “Because the Earth is oriented in space in such a way that the hemispheres are out of phase in terms of the amount of solar radiation they receive, it is surprising to find that the climate in the Southern Hemisphere cooled off repeatedly during a period when it received its largest dose of solar radiation,” says Singer. “Moreover, this rapid synchronization of atmospheric temperature between the polar hemispheres appears to have occurred during both of the last major ice ages that gripped the Earth.”

    2) Unexplained change from a 41,000 year cycle to 100,000 year cycle. How does one explain the observation that the glacial/interglacial cycles started with a cycle periodicity of 41,000 years in duration and then 1.6 millions ago the cycle time changed to a cycle of 100,000 years (90,000 years glacial and 10,000 years interglacial.)

    http://en.wikipedia.org/wiki/Milankovitch_cycles#/media/File:Five_Myr_Climate_Change.svg

    2) Orbital eccentricity is the weakest of the orbital cycle modulation on insolation. Why does it dominate for the last 1.6 million years?

    3) The stage 5 glacial was terminated 10,000 years before the insolation change. There is no cause for that change. There is no back up forcing mechanism to terminate glacial periods.

    4) There is evidence in the paleo climate data of cyclic abrupt climate change. (Heinrich events, such as the 12,900 years BP Younger Dryas abrupt cooling event.) There is no forcing mechanism that explains the cyclic abrupt, very large climate changes.

    5) The glacial and interglacial periods end abruptly. The paleo record supports the assertion that the mysterious cyclic abrupt climate forcing function terminates both the glacial and interglacial period. Insolation changes are gradual.

    An example of an abrupt climate change is the Younger Dryas abrupt climate change at 12,900 BP. Solar insolation at 65N was at this interglacial maximum when the planet abruptly cooled going from interglacial warm to glacier cold, with 70% of the cooling occurring in less than a decade. The YD cooling period lasted for 1200 years.

    6) The cycle abrupt climate change cools both the Southern Hemisphere and the Northern hemisphere synchronously. This does not make sense at the Southern Hemisphere has maximum insolation in the summer when the Northern Hemisphere has minimum insolation in the summer.

    7) Recent analysis has soon the geomagnetic has changed in synchronous with recent climate changes (Last l000 years). The geomagnetic field is abruptly changing in orientation and strength correlating with planetary temperature.

      • A more oblique axial tilt does not imply more insolation in the northern hemisphere. Both hemispheres get the same insolation over the course of a year.

        At 0 degrees oblique tilt, the sun would appear to circle the horizon all year at the poles (but this condition is outside the range of variation in the axial tilt). At 22 degrees, part of the north polar region is in a six-month night while the same size region at the south pole is in a six-month day. Over the full year, both hemispheres receive the same insolation.

        The bigger the tilt, the bigger the region that experiences 6 months without insolation and 6 months without darkness.

        • Axial tilt affects the NH much more because it has land in that latitude, as I’d have thought obvious. Then build up of ice sheets affects albedo.

  19. So much ice melt must correspond to quite a significant absorption of heat into the ocean. If the ice didn’t melt, the atmospheric temperature would have increased 40 °C (very rough guess).

    I can only see a rapid end to glaciation if there is a lot of rain causing a massive decrease in albedo of the ice sheet.

  20. On eccentricity, Jupiter cannot cause it by gravitational pull, because Earth has an entirely different orbit and the ellipse is almost static. Jupiter has a twelve earth year orbit. Best guess, and I mean guess for a candidate is “planet 9”, So where’s the real myth?

  21. The CO2 political statements in this article turn it from an informative read to an awkward one (“Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.”). It always happens when they Frankenstein in the obligatory political correctness.

  22. Many in the west worry about melting glaciers, but few consider how old they are, but if you do you will see that many modern glaciers first formed over the last 4000 years ago as the Holocene began to cool. The oldest ice in the Hans Tausen Glacier in Northern Greenland first formed ca. 4,000 years ago; Mt Churchill in Alaska ice some 2,500 years ago; Quelccaya in Peru began its current existence 1,500 years ago; Kilimanjaro dates are less certain and are somewhere between Quelccaya and the Fremont Glacier in Wyoming, which is only 300 years old. New glaciers are forming closer and closer to the equator as the planet begins to cool inexorably into the next ice age. This is from John Kehr’s Inconvenient Skepic and to date, I have not seen it seriously questioned, let alone discussed. And this cooling has been accompanied by rising CO2 …. Curiouser and curiouser said Alice …

    • When glaciers grow in Tennessee.

      H/t to the late, great Freeman Dyson
      ===============================

  23. “Milutin Milanković, a brilliant Serbian mathematician and climatologist, postulated in 1941 that variations in Earth’s orbit could push the planet’s climate in or out of an ice age.1 Vital to that idea is the amount of insolation—incoming solar radiation—at 65° N, a bit south of the Arctic Circle. At that latitude, insolation can vary seasonally by 25%. Milanković argued that reductions in summer insolation allow some winter ice to survive. Each year for thousands of years, ice accumulates around 65° N and eventually forms sheets large enough to trigger an ice age.”

    That “…insolation can vary seasonally by 25%.” might sound impressive, but it’s not. That amount sunlight reaching the land surface at 65 degree latitude is very low.
    If you go from 65 degree latitude to 60 degree latitude there will be significant increase in the amount sunlight striking the surface. But there not much sunlight striking the surface at 60 degree latitude or even at 50 degree latitude.
    To collect solar energy at 65 degree latitude, you tilt the angle of solar panels to collect more sunlight, as compared to having level with the surface. I would guess the tilt would be somewhere near 45 degree so that the sunlight hit panel surface near perpendicular. So at 65 degree latitude if have a surface at angle where sunlight hit somewhere near perpendicular, the surface will get more energy per square meter, as compare to the surface of the land- much more 25% difference. If did same thing at 60 degree latitude, the tilt could be about 40 degree rather than 45 degree {or at 40 degree latitude the tilt would 20 degree rather 40}.

    Now don’t have to go up to Arctic to see this. It happens every day where ever you are, you get the sun low above the horizon in the morning and when near sunset.
    When Sun is directly above the equator it is the equinox, sun at noon at will at 90 degree and if at 65 degree latitude and at noon it is 90 – 65 or 25 degree above the horizon at noon.
    Back to equator at equinox, you will have 12 hour day and night {roughly speaking this also true all over the world- a equal amount of day and night} anyhow at equator, the sun rise 15 degree per hour. And if at noon,
    in 6 hours it will be sunset: 6 times 15 = 90, sun will from 90 degree to 0 degree in 6 hours. Every else in world will be sunset in 6 hours. But at 65 degree latitude, the degrees it lowers per hour is roughly, 25 / 6 = about 4.1
    degrees per hour, the sun lowers {or it’s flatter arc].
    With that is mind, one has rough guide call peak solar hour. If at equator is easier, you have 6 hours in middle of day in the sunlight is the strongest- 3 hour before and after noon. Or since noon is 90 degree, when sun is 45 degree or more above the horizon. At noon the sunlight could be about 1050 watts per square meter, and 3 before or later it about 800 watts per square meter and doesn’t matter much whether you talking about level ground or pointing something at the Sun. But it does matter more when sun is before and after the peak hours. At 4 hours before or after noon, the sun is at 30 degree above the horizon, and sunlight must pass thru about 2 times more atmosphere as compared to when sun is at noon, and there ever increasing amount of atmosphere the sun has to pass thru. And terms of level surface, the sunlight spread out over large area, or someone standing will cast ever longer shadows when sun get lower 30 degrees above horizon.
    Now at equinox, at 60 degree latitude, and at noon, the sun at 30 degree above the horizon {and when goes towards summer it peaks + 23.5 degrees, or 53.5 degrees above horizon at noon and you long daylight hours
    and significant amount of time {hours} when the sunlight is at or above 45 degree above the horizon- or sun does NOT lower by 15 degrees per hour- it’s a flatten arc [as it was at the equinox}, And if sunlight is 45 or higher above horizon, the sunlight is not spread out over surface much {or your shadows are not to too long}
    or guess one getting about 700 watts per square meter of insolation upon the surface- or ground may warm up to 30 to 40 C. But if go 5 degree up to 65 degrees latitude, it’s 53.5 – 5 = 48.5 degree above the horizon.
    So you two factor and these factors quite significant when sun is lower than 30 degrees above horizon and in transitional zone from 30 to 45 degree. Or the 5 degrees different in the tilt is significant difference in terms of
    insolation.
    But I don’t think it’s a significant effect on whether one has glaciers or not. The average air temperature is important- and how dry it is and both these factors can be far more important.

    • Now, article does say this:
      –Runaway positive feedbacks froze most of Earth’s water billions of years ago during snowball Earth events, but moisture limitation has prevented a more recent episode. Forming an ice sheet requires a cold, wet climate. —
      I don’t agree about snowball earth myth, but this part:
      “Forming an ice sheet requires a cold, wet climate. ”
      I might say even “cool”, wet climate could give ice sheet. But we go with “cold” especially since think most
      of Earth presently is pretty cold {it’s just in the context that others are imagining Earth is too warm- or we aren’t in Ice Age and people imagine that 15 C is warm}.
      So how do get more “cold, wet climate”.
      I think if entire ocean was warmer, one would get more cold, wet climate. And you get warmer, wet climate. Or Canada average year temp is minus 4 C, and if Canada got wetter, it’s average could rise to 0 C, and in northern parts of Canada, one could get more glaciers.

  24. Celestial Mechanics, better said
    Et ex machina caeli tempestatibus.
    Deus ex machina?
    Sure the solar system is a mechanical system, and that appeals to our modern Cartesian machine culture.

    Only problem is, there is a much bigger, grander system, of which this solar system is but a tiny cog – the galaxy. And Svensmark, Shaviv found that is quite something else – a vast cosmic radiation system.

    Milanković in 1941 simply predates our nuclear age.

  25. Just exactly what is an “ice age”? Presently there are almost 200,000 glaciers on planet Earth and the poles retain a great deal of ice year around. In northern hemisphere winter 30% of the landmass is covered with ice and snow. So, what’s the deal, does NYC have to be under ice to qualify as an ice age?

    • Ice Age or icehouse climate is cold oceans and polar ice caps, we have in Ice Age for millions of year and the last million has been the coldest.
      Some people say glacial periods are ice ages.
      Some people claim there has been colder periods on Earth which are called Snowball or Slushball Earth.
      But most of last 500 million year of Earth history has had much warmer Oceans then we have currently.
      The warmest states are called Hothouse climate and they have very warm oceans.
      I am unaware of any Hothouse climate which didn’t involve a very unusually large amount of volcanic activity- and would think the type of volcanic activity which is forming and has form the Hawaii island chain as not a very large amount of volcanic activity.
      But would count the island formation of Iceland as involving unusually large amount of volcanic activity:
      “The pocket of magma that sits beneath Iceland is thought to be what created the island, as hot lava rose to the surface of the ocean, where it cooled and gradually accumulated into an island beginning about 70 million years ago, according to San Francisco’s Exploratorium museum.”
      And Hothouse climates, geologically speaking are short periods of time.

      • There were ice ages during the Late Ordovician-Early Silurian when CO2 was ca.7,000ppm
        A very long ice age during the Late Carboniferous – Early Permian and a small one in the Late Jurassic when CO2 was 1,500 ppm

        • The coldest temperature ever recorded was −89.2 °C at the Soviet Vostok Station in Antarctica on 21 July 1983 by ground measurements.

          How cold do imagine temperatures have ever got to on land on Earth.
          I would guess it occurred during our last glaciation period when polar sea ice was at it’s greatest extent at southern polar region.

  26. Since the Pleistocene Ice Ages started ~ 2.5 million years ago and for all of the preceding ~65 million year long Tertiary period Earth’s climate did not experience any Ice Ages, it seems as if something happened at the end of the Tertiary period that changed 1 or all 3 of the variables of Earth’s orbit Obliquity Eccentricity and Precession. Any thoughts on this?

  27. “Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.”

    Uh…No.

    Clearly GHGs are responding to changes in ocean temperature – just look at the lags. If you can cool off even ocean water that it can absorb a substantial amount of CO2, then you have the correlation observed in the record. Reduced CO2 *might* be a feedback to further cooling, but there is no mechanism where it can start the entire chain off. Think about it, where does the atmospheric CO2 disappear to if it isn’t into a cooler ocean? And if you can’t have cooling with lot’s of atmospheric CO2, how the heck does the entire process start? So, first there is cooling and then CO2 is absorbed – very straightforward.

  28. Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.

    A shameful lie.

  29. Javier, who has commented at WWUT in the past, wrote an extensive series of posts at Judith Curry’s site under the title “Nature Unbound”. The first of the series which has at least 10 parts begins as follows:

    Nature Unbound I: The Glacial Cycle
    Posted on October 24, 2016 by curryja | 269 Comments
    https://judithcurry.com/2016/10/24/nature-unbound-i-the-glacial-cycle/
    by Javier

    Insights into the debate on whether the Holocene will be long or short.

    Summary: Milankovitch Theory on the effects of Earth’s orbital variations on insolation remains the most popular explanation for the glacial cycle since the early 1970’s. According to its defenders, the main determinant of a glacial period termination is high 65° N summer insolation, and a 100 kyr cycle in eccentricity induces a non-linear response that determines the pacing of interglacials. Based on this theory some authors propose that the current interglacial is going to be a very long one due to a favorable evolution of 65° N summer insolation. Available evidence, however, supports that the pacing of interglacials is determined by obliquity, that the 100 kyr spacing of interglacials is not real, and that the orbital configuration and thermal evolution of the Holocene does not significantly depart from the average interglacial of the past 800,000 years, so there is no orbital support for a long Holocene.

    • If any of you are in communication with Javier, please ask him to read the post above and comment on it.

  30. It has always seemed to me that astronomical theories of the cycles of stadials and interstadials have been a problem for GHG driven Climate Change theorists.

    The occurrence of a stadial would be a far bigger problem for humanity and the biosphere than any plausible warming scenario.

    I could easily adjust to the world being 2 or 3 °C warmer than it is now. I would just have to invest in a backyard swimming pool.

    But having my house covered by a mile thick sheet of ice, as it was during the last stadial. That would be a problem.

    If humanity by burning fossil fuels is preventing the return of the next stadial, we are doing a very good thing. And, we ought to pick up the pace.

  31. Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.

    Maslin backs up this statement with a single reference only, by Jeremy Shakun of Oregon State University:

    https://www.nature.com/articles/nature10915

    Shakun’s notorious “study” is an egregious hatchet job on palaeo climate data. This study looked at only the single most recent deglaciation – the Holocene inception. Two elements combine to allow Shakun et al to flourish like a rabbit out of a hat, the bizarre conclusion that CO2 increase has preceded glacial termination.

    1. Shakun trawled through no fewer than 80 climate “proxies” of the last deglaciatuon to the Holocene. These included a host of highly dubious biological proxies – pollen, insects, plant based etc. The timelines of these proxies in the full version of Shakun’s research show that many of them are so weak that they scarcely resolve a difference between the last glacial maximum and the Holocene optimum. Critically, some biological proxies show delayed change after the glacial melt and rising sea level. Many are very imprecise. The effect of including so many such proxies is to delay the apparent beginning of the Holocene to allow the conclusion that CO2 increased before temperature increased.

    2. The second part of Shakun’s trick was to take advantage of the unusual nature of the last deglaciation. Namely, the Younger Dryas (YD). There was an interrupted start to the Holocene (casting doubt on when it actually began). Northern Hemisphere and Greenland warming began sharply about 14,500 years ago with the episode called the Bolling-Allerod. After this there was a sharp reversal to cooling – the YD – a northern hemisphere only phenomenon in which the North Atlantic cooled back to near glacial temperatures for 1000 years or so, due to a cut-off of the AMOC. This eventually came to an end about 12,000 years ago when the Holocene finally started in earnest in the NH.

    However, hidden behind the magician’s cloak is the face that the real initiation and causative driver of the Holocene glacial termination was not in the northern hemisphere at all, but was Antarctica. All major climate shifts start in the ocean and this was no exception. Southern ocean warming around Antarctica had begun as early as 20,000 years ago – while the northern hemisphere was still in the grip of the last glacial maximum. This is shown by this paper by Weaver et al:

    http://home.sandiego.edu/~sgray/MARS350/deglaciation.pdf

    This is the real start of the Holocene. The blogger Javier who has posted extensively on this subject previously here and on climate Etc., showed convincingly that interglacial initiation is always preceded about 6000 years earlier by a peak in obliquity (accompanied by an eccentricity maximum, following the MPT). This gradually starts deep ocean warming. The world’s largest ocean is the southern Ocean (there is less land in the SH). A full 35% of the ocean’s volume is the Antarctic bottom water (AABW).

    Eventually slow Antarctic Ocean warming caused the Bolling Allerod (BA) warming in the NH. But after 1000 years this reversed to YD cooling. The important thing is that the YD cooling was in the NH only – the Antarctic continued to warm during the YD. The cause of the YD reversal is disputed – there is an impact hypothesis, although it is more likely that it was an oceanographic process linked to a catastrophic Antarctic ice sheet collapse, which caused the brief “Antarctic cold reversal” about the time of the BA and perturbed deep Atlantic circulation.

    An important feature of ocean driven climate especially at around Holocene inception, is the “bipolar seesaw” the phenomenon of alternating warming and cooling in inverse phase between the SH and NH. This is caused partly by the delay in starting of slow ocean processes, and also a big difference between the NH and SH in their stability – the NH is more unstable due to the AMOC (Atlantic meridional overturning circulation) which has the habit of unexpectedly turning off and on again. This instability is due to the salinity-Arctic downwelling feedback. By contrast, ocean changes are more smooth and slow in the SH.

    Putting all this together, you have a scenario where Antarctica warmed steadily from about 20,000 years ago. Albeit with a brief interruption at the ice sheet collapse and the cold reversal. The warming of the huge volume of the southern ocean released CO2 into the atmosphere. This is why CO2 continued to rise throughout the YD, while NH glacial termination was experiencing a “false start”. (The YD could be regarded as simply the last of about 20 Dansgaard-Oeschger DA warming excursions that happened throughout the last 80,000 year glacial interval – all arising from AMOC instability.)

    So combine this ongoing Antarctic ocean warming during the anomalous YD, together with a spurious delay to the northern hemisphere Holocene inception by mixing in so many dubious biological proxies, and Shakun and colleague are able to get to the “Prestige” moment of their conjuring trick: the false conclusion that CO2 preceded Holocene inception. This was achieved by deliberately blurring over the complexity and SH-NH interplay of the Holocene inception.

    The result is this fraudulent marker in the literature – Shakun et al 2012, allowing Maslin and others to make the one reference only claim that CO2 precedes warming, created by smoke and mirrors at the last deglaciation and then generalised to all deglaciations.

    Aside from that flawed study, the consensus of geology including ice cores at both poles from all deglaciations is that warming happens first, then CO2 increase from the outgassing oceans.

  32. I have a hunch that Milankoviç cycles need to be overlaid with sun spot activity, in order to improve the fit where it seems to go slightly astray.

    Unfortunately I do not have the wit to go about this.

    It would be nice to blow this GHG nonsense out in one fell swoop. I’m getting very bored of it now – it is highly damaging as much as tiresome.

  33. Almost anything out of most universities these days are lies, but at least the mechanics of Maslin’s study seem pretty good — obliquity does indeed rule. But this has already been well-analyzed on Climate Etc.

  34. https://science.sciencemag.org/content/299/5613/1728
    CLICK ABOVE – NOT QUITE CORRECT – WAY OFF ACTUALLY – a much longer way off – temperatures very likely increase 1st – then CO2 gas concentrations increase in the ice cores – yes back to the soft drink bottle – in and out of the fridge – basic chemistry of gases in cold oceans as opposed to warming oceans

    The sequence of events during Termination III suggests that the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years and preceded the Northern Hemisphere deglaciation.
    https://science.sciencemag.org/content/299/5613/1728

    Global warming preceded by increasing
    carbon dioxide concentrations during the
    last deglaciation – from Harvard via Nature – https://projects.iq.harvard.edu/files/climate/files/shakunetal2012.pdf
    note these are old references – the very information no one broadcasts any more – or if they do – they risk losing their jobs or not getting any more funding – which can equate to the same thing

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