The dog that did not bark

Guest post by Peter Morcombe

Remember the case of “Silver Blaze”?  Here Sherlock Holmes discusses it with a Scotland Yard detective:

Gregory: “Is there any other point to which you would wish to draw my attention?”
Holmes:  “To the curious incident of the dog in the night-time.”
Gregory: “The dog did nothing in the night-time.”
Holmes:  “That was the curious incident.”

Why did the dogs fail to bark?

Just a few weeks ago I finally got around to looking at some papers relating to the EPICA “Dome C” ice cores.   My interest stems from the idea that temperature changes are presumed to be magnified at high latitudes so it ought to be easier to measure “Global Warming near the poles.   An earlier review of Greenland’s climate found an average temperature rise of 2.3 K since 1850, almost three times higher than the IPCC’s “Copenhagen Diagnosis” (0.8 K)

Ice cores provide an excellent record of past temperatures plus data on CO2, Methane, and volcanic dust.  As the GISP ice cores go back only 130,000 years one might assume the climate was much warmer back then than it is today.  This idea gets support from the EPICA ice cores that show the last Interglacial to be about 2 K warmer than the present one.  This diagram below can be found at  Wikipedia:


The separation between the Vostok and EPICA traces results from Vostok averaging ~6 K colder than EPICA.    Let’s take a closer look at the EPICA record that extends almost 800,000 years into the past.  In particular what do the EPICA researchers have to say about the relationship between CO2 and temperature?   Here is Figure 2 from Luethi et al. (2008).

Figure 2 from Luethi et al.

The abstract contains this statement:

“From previously published data1, 2, 3, 4, 5, 6, 7, 8 and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles….”

While this is clearly correct, the researchers do not claim that CO2 is the cause of the changing temperature.

Why did the dogs fail to bark?

Epica post fig 1

The light blue plot shows the EPICA temperature file while the red plot is temperature calculated from the CO2 concentration [CO2] using the Arrhenius theory that CO2 is a primary “Greenhouse Gas”:

Temperature Anomaly = ΔT = A * log2 ([CO2]/280)……..Where A is a constant representing K/Doubling of [CO2].

The striking correlation over such a long period of time must mean something.  So why is it not being trumpeted as a strong argument in favor of Arrhenius?   The researchers could answer this question but they tend to “Lawyer Up”.  For example, Thomas F. Stocker one of the researchers is fighting Steve McIntyre’s  efforts to gain access to the deliberations the IPCC’s “Climate Scientists” (Working Group 1) who are working on the AR5 report due for publication in September.   So let’s try to figure out what the problem is without their help.

Epica Post Fig 2

Fig 2. uses the same data as Fig 1. but only the last 2,500 years are displayed.  If “Climate Scientists” had used the EPICA data to vindicate Arrhenius they would need to explain why the Keeling Curve Hockey Stick (CO2 concentration) did not produce the expected 8 K temperature rise in the last 160 years.  The actual “Global Warming” since 1850 was only 0.8 K, an order of magnitude less than than the EPICA data suggests.

Unanswered Questions

To make the calculated data in Fig 1 (red plot) agree with the measured data (blue plot) I had  to set the sensitivity constant to 16 K/Doubling of CO2, whereas to make the modern data fit (1850 to 2013) observations the sensitivity constant needs to be 1.6 K/Doubling.  Who can believe that the sensitivity constant remained at 16 K/Doubling for 800,000 years and then suddenly changed to 1.6 K/Doubling in 1850?

There is an explanation that makes sense.  The fluctuation of CO2 concentrations over the last 800,000 years were caused by fluctuations in ocean temperatures.  The solubility of CO2 in sea water is a function of temperature.  This hypothesis also accounts for the 500 year delay between rising temperature and rising CO2 concentration.

That still leaves the question of what caused the temperature changes associated with the last eight glacial cycles.   Many people think that Milankovich cycles are responsible for the recent ice ages but the mathematics is a little shaky.  Do you know anyone who can tell you when the next glaciation will start based on Milankovich’s theories?

It also leaves the question “What caused the 0.8 K global warming since 1850”?   If CO2 lived up to Arrhenius’ expectations we would be in no doubt at all.

Peter Morcombe (gallopingcamel)


  1. Luethi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker (2008).  High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382, 15 May 2008.  doi:10.1038/nature06949
  1. Jouzel, J., V. Masson-Delmotte, O. Cattani, G. Dreyfus, S. Falourd, G. Hoffmann, B. Minster, J. Nouet, J.M. Barnola, J. Chappellaz, H. Fischer, J.C. Gallet, S. Johnsen, M. Leuenberger, L. Loulergue, D. Luethi, H. Oerter, F. Parrenin, G. Raisbeck, D. Raynaud, A. Schilt, J. Schwander, E. Selmo, R. Souchez, R. Spahni, B. Stauffer, J.P. Steffensen, B. Stenni, T.F. Stocker, J.L. Tison, M. Werner, and E.W. Wolff (2007).  Orbital and Millennial Antarctic Climate Variability over the Past 800,000 Years.  Science, Vol. 317, No. 5839, pp.793-797, 10 August 2007.
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32 Responses to The dog that did not bark

  1. Verity Jones says:

    I’ve tried fixing the last two figures, but to know avail. I guess people can click on them to view properly.

  2. crosspatch says:

    Many people think that Milankovich cycles are responsible for the recent ice ages but the mathematics is a little shaky. Do you know anyone who can tell you when the next glaciation will start based on Milankovich’s theories?

    I don’t believe that the Milankovich cycles are *directly* responsible for the switch between states but I do believe they set the stage or conditions that allow the switch to take place. I believe our climate in the Northern Hemisphere has two stable states, a cold state where glaciation occurs and a warm state where the glaciers retreat and we have a relatively mild climate over most of the Northern Hemisphere. I also don’t believe that the glacial periods are quite as pronounced in the Southern Hemisphere as in the Northern, basically due to geography.

    I also believe there is some hysteresis in the system so that when conditions are such that we could remain stable in the glacial state if we were already in it, some additional “kick” is needed to push us over the edge into that state. We are probably in a situation right now where we could remain stable in the glacial state should be be pushed into it. NH summer insolation is probably low enough now to sustain a glacial condition but we haven’t tipped into that state. We also know that the conditions of the Little Ice Age were not quite enough to do it. We probably needed to go a bit colder to get there. It is my opinion that it is early/late season NH snow cover or Arctic ocean summer ice area that tips us over the boundary or a combination of the two. In other words, something happens when insolation falls that causes a high albedo condition from which we can’t recover.

    Note that tropical insolation doesn’t change much during glacial periods. Something must happen that changes (reduces) ocean transport of heat from the tropics to the poles and we see the atmosphere take over more of that transport. This causes changes in storm tracks, particularly in winter, resulting in greater snow pack in the spring when sun angles are high and more energy is reflected into space. Also, if the Arctic Ocean sees a summer with much larger ice cover than normal, we again see a great amount of summer energy reflected back into space. I am pretty much convinced that it is the loss of Arctic Ocean summer ice cover that flips us out of the glacial state but not sure what role it plays flipping us into it. The Arctic Ocean having a lot of open water, even while the surrounding land is still covered with ice, would result in a lot of energy absorbed into the ocean when we are at a point in the cycle where NH insolation is higher than today.

    So when we are in a glacial state, insolation is increasing toward the end of the glacial and we get long past the point where we could sustain interglacial conditions but need something to kick us across the hysteresis boundary and that might be the sudden melting of the ice cover on the arctic ocean coupled with the lower latitude melting which is raising sea levels which is causing what was landfast ice to float off the bottom and be blown about by the wind. Each time that happens, the albedo decreases a bit more causing positive feedback which increases the energy in the system.

    There is, I believe, a canary in the coal mine. Watch the Columbia snow field in Alberta. When the Athabasca glacier starts a mighty advance, that’s your cue.

  3. peter azlac says:

    The Milankovitch cycles (actually first proposed by James Croll) are important but the main event is the movement of the solar system around the centre of the Milky Way that affects the flux of cosmic rays and hence albedo via cloud cover. The reducing length of the glaciation periods may be due to the lack of symetry in the arms of the Milky Way but also the position of the solar system as it orbits above or below the plane of the galaxy. We are now passing through the plane so may well be at the tipping point! All this is explained by Shaviv Nir who has found evidence in the geological record:
    ‘Nir Shaviv, an astrophysicist at the Hebrew University of Jerusalem, visited Toronto and told Veizer that cosmic rays striking the Earth cycle up and down over 135 million years as our solar system passes through one of the bright arms of the Milky Way. The Milky Way arms have intense levels of cosmic rays that tend to cool the Earth by stimulating the formation of those low-level clouds that reflect solar radiance back into space.
    In a cross-disciplinary study recently published by the Geological Society of America, Veizer and Shaviv conclude that 75 percent of the Earth’s temperature variability in the past 500 million years is due to changes in the varying bombardment by cosmic rays as we pass in and out of the spiral arms of the Milky Way. They write, ‘Our approach, based on entirely independent studies from astrophysics and geosciences,yields a surprisingly consistent picture of climate evolution on geological time scales. The global climate possesses a stabilizing negative feedback. A likely candidate for such a feedback is cloud cover.’

    Of course this movement of the solar system re the Milky Way will also have effects on the tidal forces on the Sun due to the planets ( especially Jupiter and Venus) and so influence events in the stratosphere via changes in ozone level that would affect the strength of the Trade Winds and so the level of evaporative cooling of the tropical ocean via convection – the data suggests it falls only by a marginal amount during glacial periods, but that will be sufficient to affect heat flow to the NH via ocean currents and atmosphere. There would also be effects on Rossby waves that would, as know, lead to Meridonal circulation with cooling. But, as the article states, CO2 would have bupkis to do with this!

  4. peter azlac says:

    Nir Shaviv

  5. David Appell says:

    Peter Marcombe is a known liar.

    Why is he still allowed to post here?

    • gallopingcamel says:

      Thanks for sharing your opinion. Do you have any evidence?

      • David Appell says:

        I don’t allow dishonest people to keep commenting at my blog, as Peter Marcombe found out. Why does this blog?

      • David Appell says:

        Sure. You said Sagan explained Venus without a greenhouse effect, and then you claimed the opposite.

        You don’t know what you believe.

      • David Appell says:

        Not surprised you didn’t reply or defend.

        People, you are not debating with an honest presenter…. He will alter his argument without the slightest indication he once said otherwise….

  6. gallopingcamel says:

    Crosspatch and peter azlac,
    This post was intended to stimulate some speculation on the “Big Picture”. Your ideas make sense to me. Some combination of cosmic rays or Milankovitch cycles may be the key to understanding the recent glaciations.

    The recent past (~12,000 years) has been remarkably stable. Yet, when you look back over the last 800,000 years the climate has changed very rapidly, suggesting strong “Positive Feedbacks”.

    When ice cover is expanding, Earth’s albedo rises owing to the high reflectivity of ice while cloud cover falls owing to reduced evaporation. It is easy to imagine that these processes constitute positive feedback owing to the rejection of incoming solar radiation on the one hand and the increased loss of outgoing thermal Infra-Red radiation on the other.

    When most of the planet is covered in ice (Iceball Earth) the bad news is that most land masses are arid icy deserts. The good news is that positive feedback has reached a limit so it is not going to get any colder. What really puzzles me is why the glaciation is interrupted by warm periods.

    The EPICA researchers made a good call. They knew that any hypothesis claiming the recent Ice Ages were driven by CO2 would be an embarrassment. They decided to claim that CO2 “amplified” the effect of whatever caused the Ice Ages as proposed by Jeff Severinghaus, one of the EPICA researchers:

    I made several attempts to discuss this idea with Severinghaus. Severinghaus was also a co-author of the Kobashi et al (2008) paper that reconstructed temperatures in Greenland. My efforts to establish a dialog were even less successful than Steve McIntyre’s. As far as I know the only member of the EPICA research team who will communicate with the general public is Thomas F. Stocker who is working with Phil Jones to obstruct enquires made under FOIAs (Freedom of Information Acts) or the Aarhus Convention.

  7. peter azlac says:

    I should have added to my recent post that there is a very readable and well illustrated article on the impact of the Earth’s passage through the Milky Way and Ice Ages at Nir Shaviv’s blog site, as well as other papers on this topic. He is a real scientist in contrast to many in the climate science industry!

  8. w.w.wygart says:

    In case you missed it, Michael Hart makes an interesting comment over at TallBloke on April 30th about the equilibrium absorption rate of CO2 in sea water which may be relevant to what you said under Unanswered Questions: “The solubility of CO2 in sea water is a function of temperature”. I’ll quote in part:

    Solubility in seawater is much more than simple diffusion of the gas across the phase boundary into, and dissolution in, water, as per Henry’s law. At oceanic pH, most of the CO2 ends up as HCO3-, bicarbonate, and that’s partly why the ocean is such a huge sink. I would expect the rate of dissolution of CO2 to quite possibly be limited not only by CO2 diffusing into water, but by the rate at which it is converted into bicarbonate, which is about 7 powers of 10 (i.e. 10,000,000 times) SLOWER than a diffusion-controlled maximum reaction rate set by the Einstein-Smoluchowski limit. Note that while increased temperatures do drive the dynamic equilibrium towards the right hand side of the reaction:
    (H+) + (HCO3-)=(H20) + (CO2)
    -higher temperatures also increases the RATE of interconversion between the two species and hence the RATE at which equilibrium is approached from either side.

    The practical upshot of this is that at higher temperatures, despite a slightly unfavourable shift in the equilibrium position, CO2 can dissolve FASTER in aqueous solutions that are not close to equilibrium. That is, the sink potentially becomes BIGGER because it never was at equilibrium.

    I thought it was an interesting and relevant idea, though of course I cannot evaluate it.


  9. George B says:

    The Milankovitch cycles (actually first proposed by James Croll) are important but the main event is the movement of the solar system around the centre of the Milky Way that affects the flux of cosmic rays and hence albedo via cloud cover.

    While I certainly believe that plays a role, the cycle of that event is much longer than the roughly 125ky cycle we see with glacial periods. It is simpler than that, I think. For example, once we get into a situation where NH insolation is low enough to support remaining stable in the “cold state”, it takes something to trigger that. It probably takes a combination of things. For example, we might be in an insolation regime for 1000 or more years before the other conditions line up to “trip” us across the hysteresis into the other stable state. For example, imagine of we have an extremely quiet solar period with increased cosmic rays, increased cloud cover, and cooler temperatures but not cool enough to flip the system. We need something else such as a massive volcanic eruption and maybe just “luck” of jet stream patters.

    When we start to cool down we see several positive feedbacks as sea levels fall. The Gulf of Mexico shrinks as Florida and the Yucatan expand. The outlet of the Gulf to the Atlantic shrinks, The landmass expands in Southeast Asia and cuts off the Indian Ocean from the Pacific except for a narrow channel. Arctic ocean gets progressively shallower and reduces exchange between Pacific and Arctic but I think the key is summer ice in the Arctic. If we get two or three winters where the Arctic Ocean remains ice covered over summer, we probably flip the system. Once those things happens the primary mechanism of heat transport from the tropics to the poles shifts from ocean to atmosphere.

    Remember that tropical insolation doesn’t change much. It is high latitude insolation that changes making the delta energy input between tropic and arctic much greater.

    Mitigation of this late interglacial are that we are going to see a slight uptick in insolation before it drops again and our orbit around the sun is about as close as it gets to circular and currently getting more so.

  10. peter azlac says:

    George B
    Your points are valid and very probably a part of the cooling cycle but we are looking for the trigger and this has to be a change in global heat distribution as solar TSI does not vary much, and has increased by around 30% since the “Faint Sun” period. The only way for this to occur is for the heat distribution system to be disturbed and that means a) reduced TSI at the surface b) increased OLR at the TOA or c) reduced heat distribution from the equator to the Poles, especially the Arctic, or a combination of all three plus any other unknown.

    The two mechanisms I know of that can achieve this are changes in cloud type, cover and distribution, hence albedo, and the strength of the winds in the stratosphere that affect the NAM and SAM – currently a reduced NAM is the current NH cold winter by a switch to meridional circulation – this also affects the positions of the Hadley and Terrell cells and so evaporative cooling by convection – Stephen Wilde has good papers on these events.

    Nir Shaviv and Veizer have shown that such effects occur during normal solar cycles linked to the strength of the solar wind that modulates cosmic ray flux, such that we only have to have a weakening of the solar wind, as now with a quiet Sun, to have a substantial effect on albedo and the cooling process. At the same time the cosmic rays received from the arms of the Milky Way are not of constant strength but vary with the position of the Solar System in relation to the arms, such that a confluence of a very quiet Sun and increased cosmic ray strength can be a sufficient cause of any tipping point,

    The reducing length of glacial periods does however suggest some other mechanism may be at play, though this fits with the increased solar activity over the same periods.

  11. George B says:

    Your points are valid and very probably a part of the cooling cycle but we are looking for the trigger and this has to be a change in global heat distribution as solar TSI does not vary much, and has increased by around 30% since the “Faint Sun” period.

    While the TSI does not vary much, the distribution of energy across the spectrum DOES vary considerably, particularly in the UV. But there is probably one one single thing, it is probably several things. During the faint sun period, Earth was more geologically active with volcanoes. One might expect to have had a thicker atmosphere. That would make the surface warmer simply through the adiabatic lapse rate. During the faint sun period, all of the CO2 that is currently locked up in limestone, chalk, marble, coal, etc. was in the atmosphere. Those white cliffs of Dover are quite literally solidified air.

    But the ice ages of the past few million years are probably due to geographical causes that resulted in changes in ocean currents, the cutting off of the equatorial Pacific / Atlantic in particular. There could be other causes as well as we drift through space we might encounter varying populations of cosmic rays.

    Long term changes in solar activity can’t be ruled out, either. We have only been studying the sun for a very short period of time. We have two periods in the past where we have documented contemporary accounts of “weak sun” conditions that correspond to breakdowns of civilization. These would be the period of the Greek Dark Ages that corresponds with the Late Bronze Age Collapse of civilizations generally and the more recent European Dark Ages in the 6th century. We have speculated that this is due to volcanic activity but we just don’t know. We also don’t know what impact large variations of solar UV energy have on our climate.

    So what we have are large overall changes that tend to set conditions over several million years and smaller changes that act over shorter periods of time. Even during glacial periods we see some rather dramatic interstadials where temperatures rise to near modern day levels and we don’t understand why. There are also positive feedbacks involved where changes in ocean levels cause changes in exchange of water from various basins. Lowering of sea levels cuts off or reduces circulation from some places. Energy transfer shifts from oceanic to atmospheric and when this happens, maybe we get the mother of all snowstorms raging across North America and Europe. We also get a slight migration of the location of the rotational pole as ice mass builds up in North America and the pole moves toward Ellesmere Island which in effect moves much of North America some 300 miles farther North (and parts of Eurasia some 300 miles farther South).

    It is a very complex system and several things are changing at the same time. I really don’t think we are going to find the “magic bullet” that ties it all together though we might finally get the one condition on top of all the others that breaks the camel’s back. For example, had Krakatoa erupted in the mid 1700′s rather than in the late 1800′s, we might have tipped the system. Had Tambora erupted during the Maunder Minumum rather than during the Dalton, maybe that would have been enough. What I am saying is that we probably need:

    1. Low enough NH insolation to set the basic conditions.
    2. A quiet solar period resulting in increased clouds and lower temperatures.
    3. A trigger such as a volcanic eruption that produces a strong cooling pulse that trips us into the cooler stable state WHILE condition 2 is true for long enough to hold us there for a while so that ice can build up and begin to increase albedo and reduce sea levels.

    Once we are in that stable colder state, the removal of conditions 2 and 3 no longer matter. At that point we have built up a couple of years of snow cover and albedo is so high and insolation is so low that we can’t recover completely from it.

    Everything I have seen, though, tends to show that what happens as we go into a glacial period is that the climate signal gets “noisy” and very unstable. The system seems to oscillate back and forth several times between both states but with the general trend toward cooling.

    Also, oceans a quick to cool because cooling works with convection. Masses of very cold air coming off the continental land masses can cool a lot of water in a hurry and cause it to sink bringing warmer water which itself is cooled, etc. The result is a fairly rapid cooling of the oceans. Warming is harder to do from the surface because that works against convection. Ocean currents are probably strongest while the regime is most strongly warming or most strongly cooling, though the nature of those currents during those regimes is probably different. Once we start to stabilize, say after 50,000 years of glacial conditions, the currents probably begin to slow down. There is some evidence of this with large pools of water on the ocean bottoms in the South Pacific that were, in the last glacial, stagnant for what was apparently tens of thousands of years and not ventilated.

    During glacial periods we get huge amounts of very salty, very cold water due to brine rejection of sea ice. This water wants to sit on the bottom for a while and is hard to move.

    I guess what I am trying to say is that it is all very complex with many variables and it is only certain conditions all lining up exactly right that kick us into a glacial period (except possibly when Earth’s orbit is at maximum eccentricity and we are most distant during summer during very low NH insolation which might itself be enough). I am rather convinced, though, that it is the period if very high summer insolation when the Arctic Ocean finally becomes ice-free or mostly ice-free in summer that kicks us out of glaciation and does so quite rapidly. As NH insolation increases, the ice in the Arctic Ocean gradually thins year by year until we finally get to a point where most of the Arctic Ocean is ice free in summer. That’s when things change dramatically. Maybe then we get a pulse of fresh water from a glacial lake burst that spreads a layer of fresh water on top that freezes that flips us back for a bit before it melts but once the Arctic Ocean is ice free, we’re done for a while and are into an interglacial period.

    I’m also convinced that all of this is also due to the location of Antarctica. If there was not a major land mass sitting right on top of the South Pole, we probably wouldn’t have ice ages at all in either hemisphere. In the winter, the ocean at the South Pole would be a vortex of sinking water like the polar vortices in the atmospheres of Saturn or Venus only in our ocean. This would cause such a great circulation of water and so speed up the ventilation cycle that a lot of energy would get pulled out of the tropics to the South Pole in a hurry. The result would be cooler tropical seas but warmer polar seas and a greatly enhanced mixing of the ocean waters.

  12. peter azlac says:

    George B

    All your points are very valid and as you say it is very complicated, but the repetitive cycles suggest that we should be able to achieve a realistic understanding if we account for lunar-solar-planetary cycles, the current place of the Solar system in the Milky Way and above all an understanding of the fluid dynamics of the Earth system. The use of tools such as Bejan’s Constructal law and statistical techniques such as EMD, Fourier and Wavelet analysis is the way forward, rather than the current use of AR1 statistics. It is salutatory to note that in the mid 1800′s when Kelvin was asked to produce tide tables he ignored the physics and used Fourier analysis to establish tidal cycles and that his method and results still hold today, with the tide machines based on his work only being abandoned in favour of a digital version in the 1950′s.

  13. mwhite says:

    “180 Years accurate CO2 – Gasanalysis of Air by Chemical Methods (Short version)”

    There’s so much here, but

    “There is no constant exponential rising CO2-concentration since preindustrial times but a variing CO2-content of air following the climate. E.G. around 1940 there was a maximum of CO2 of at least 420 ppm, before 1875 there was also a maximum.”

    Who knows it may start to fall despite mans efforts?

  14. mwhite,
    The IPCC seems to agree with you. Take a look at Figure 3 on page 55 here:

    They have just about every possibility covered! It is hard to think of this kind of work as “Science”.

    peter azlac,
    I forgot the main chapter on sea level:

  15. E.M.Smith says:

    There is some confusion of the word “Ice Age”. Technically, we are in an Ice Age right now. Just having an “inter glacial” period ion one long Ice age; while those prior icy patches on the graph are properly “glacial periods” in one ice age.

    The galactic arm effect has to do with the oscillation between those times when Ice Age glacials can happen, and those times when they can not.

    Withing this one ice age the cycle of glacials and interglacies is explained by the amount of sunshine more than 60 degrees north. We’re just a couple of Watts away from the “trigger” value. We have been getting longer N. Hemisphere summers for a few thousand years now, so could keep on melting the ice. There’s a fairly good time (about 2000 years) until we get back into the ‘short summer’ cycle again, and once again are at risk of “tipping” into a new glacial. See the chart here:

    At that point, all it takes is a slow down of the Gulf Stream and we ought to “lock up” into cold. The Gulf Stream periodically slows, most likely driven by a 1400 to 1800 year lunar / tidal cycle.

    Where this graph:

    puts the next big cold spike at about 3107 A.D. to 3452 A.D. when we will have another Little Ice Age. However, the summers are most likely too long then, and will be until about 1000 years past that. Which strongly implies the next most likely “window” is about 3500 A.D. to 5200 A.D. when the summer N.H. length is lowering and we are in a cold peak for that 1500 to 1800 year cycle.

    So mark your calendar, that’s the most likely start of the next no-recoverable Glacial. The orbital processes set the table, then the lunar tidal tries to trigger it about ever 1500 to 1800 years. Once we’re average about 420 to 416 W/m^2 N. 60 degrees, then the lunar tidal trigger just needs to roll around to set if off.

    The good news is that when it happens, Florida and the Desert Southwest of the USA are nice and pleasant. The Gulf Stream back sup, and those places get nice warmth with rains.

    Yes, the precision isn’t all that great, but I think we can say about when the next glacial is most likely to commence.

    Per: David Appell:

    I think I hear a small mutt yapping in the distance. Can someone turn on the hose and squirt it?… I’m not fond of dealing with soiled trolls or I’d do it myself… (In other words, David ought not be surprised nobody responds as such insults don’t warrant it…)

    @George B:

    Yes, the major continent positions have to be “right”, but that’s an even longer process for change than the galactic arm cycle, so determines when Ice Ages are possible… (then the galactic arm triggers them… then the interglacials happen when we go above about 420 W then…)

    Personally, I find the point of the article rather interesting… a conflict between the two graphs. You can only attribute CO2 causality to ONE of them, or the inherent conflict between them causes an eruption of trouble. Interesting point and interesting problem to set before “the team”…

  16. Chiefio,
    Thanks for that stuff on Milankovitch cycles. The periods involved seem to be about right but I still don’t hear you making a prediction of when the next glacial will start. Way above my pay grade, I’m afraid!

    George B’s suggestion that re-glaciation delivers positive feedback by rejecting incoming solar radiation makes perfect sense. Finally a “Tipping Point” that might have some basis in reality. What I would expect from my non-linear circuit theory experience is that the climate would then be permanently stuck at “COLD”. We know this is not the case, so what provides the kick to start the inter glacials?

    With regard to David Appell, Verity was kind enough to grant me the power to “Zap” trolls here but I decided not to use it given that I have publicly criticized the IPCC, SkepticalScience etc, for censorship or lack of openess. He hurts his cause much more than ours.

  17. David Appell linked this:

    I found one of the comments to be a fine example of Alarmist dogma given that they are desperately looking for “Positive Feedbacks” to amplify the effect of CO2.
    CO2 is a greenhouse gas so it raises the earth’s average surface temperature. This increases the average water vapor level which also tends to warm things up.

    Nir Shaviv says that increased water vapor in the atmosphere increases the cloud cover which constitutes a net cooling (negative feedback). This makes sense to me except in the case of “Snowball Earth” where the planet’s albedo won’t be much affected by clouds.

  18. crosspatch says:

    The Milankovich cycles set the environment where we can pop out of the stable glacial state for a bit of time but aren’t the cause of the change of state. I don’t think one can say “an ice age will end on this date” or “an ice age will start on this date”. I think once the conditions are set where it is POSSIBLE for glaciation to be sustained, something else needs to happen to actually effect the change. Notice how rapidly we come out of glaciation. This is probably because conditions were such that we COULD have come out of the glaciation sooner, but something finally happened that allowed us to rapidly come out of it. I believe it is one of two things, or possibly a combination of both.

    This is my opinion that isn’t based on any great body of research:

    When we are at glacial maximum, we also have things such as sea level at minimum. This results in ocean currents being much different from what we see today. For example, there is a current that flows from the Pacific between Australia and Papua New Guinea into the Indian Ocean. That current is cut off during glacial conditions. The Gulf of Mexico is much smaller and its outlet into the Atlantic is greatly constricted. The Gulf Stream, if it exists, is farther East than it is today as the coast of the US extends all the way out to the Continental Shelf margin. The Newfoundland Banks are dry land. There is no North Sea or English Channel and Ireland is connected to Europe. Also, as more mass gets moved from the oceans at the equator to the high latitude land masses on North America and Europe, the rotational pole migrates slightly towards Ellesmere Island. This effectively moves North America a couple of hundred miles North and slightly speeds up the rotational speed of Earth.

    Now insolation begins to increase. This probably has the greatest impact initially at the margins of the ice sheets. They begin to retreat. They will advance some years and retreat in others but overall, they will begin a steady retreat. This will result in a rise in sea levels. As the sea levels rise, ice that is “land fast” will begin to be floated away. The mass will again migrate from the pole to the equator, the rotational pole will begin to migrate northward slightly displacing the North American land mass effectively southward speeding up the retreat. This continues for some period of time but isn’t really any different from what happens during other interstadials during a glacial period but something is different this time. Something changes that allows a significant warming to happen very quickly. I believe that “something” is that unlike previous interstadials during a glacial period, the Arctic Ocean finally receives enough sunlight to become partially ice free during the summer. And that, I believe, is what kick-starts the flip from glacial to interglacial. It is the open water of the Arctic Ocean, even while the surrounding landmass is covered with a mile of ice, that I think trips the system across the hysteresis barrier and into the other stable state. Without the Milankovich cycles we wouldn’t be able to come out, but geography probably plays a huge role in when we come out. If the North American land mass was positioned such that the North Pole was in the middle of Saskatchewan, we would probably be in perpetual ice age. The North Pole would be like Greenland is. But we have an ocean there that allows the ice to clear in summer during periods of high insolation.

    I also believe it is a weather pattern or volcano or solar activity or a combination of those that allows us to go INTO a glacial state but it is the Arctic Ocean remaining frozen over in summer that keeps us there. If we were to have some condition happen that resulted in a great increase in summer ice pack in the Arctic once we are at low enough NH insolation, we probably flip state. If we didn’t have an ocean there, if it was all land, we would probably never come out.

  19. gymnosperm says:

    A great mystery of nature is that there has almost always been a continent at the South Pole and there has never been one at the North Pole. Although it is tempting to consider the twitters of glacial/interglacial oscillation within our current ice age analogues for the larger scale movements in and out of the half dozen or so glacial eras we are aware of in the last billion years, the reality is that the large scale movements are irregular and that an ice free earth is the norm.

    Glacial eras have occurred in a wide variety of continental configurations. The Ordovician glacial era occurred without a major land mass at the South Pole. Until the mid-Paleozoic the northern hemisphere above the tropic was essentially continent free.

    It is also important that this whole notion of young dim and old blazing sun is based on nothing more than its status as a “main sequence” star in our current cosmology.

    Free hunch: (nothing charged, nothing guaranteed) it is the spectral distribution of TSI. Concentration in the far visible and near UV bands enjoys a window between ozone absorption and cloud reflectance that warms the oceans. The oceans rule.

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