Ancient Air Challenges Prominent Explanation For A Shift In Glacial Cycles

From Nature

An analysis of air up to 2 million years old, trapped in Antarctic ice, shows that a major shift in the periodicity of glacial cycles was probably not caused by a long-term decline in atmospheric levels of carbon dioxide.

Eric W. Wolff

During the past 2.6 million years, Earth’s climate has alternated between warm periods known as interglacials, when conditions were similar to those of today, and cold glacials, when ice sheets spread across North America and northern Europe. Before about 1 million years ago, the warm periods recurred every 40,000 years, but after that, the return period lengthened to an average of about 100,000 years. It has often been suggested that a decline in the atmospheric concentration of carbon dioxide was responsible for this fundamental change. Writing in Nature, Yan et al.1 report the first direct measurements of atmospheric CO2 concentrations from more than 1 million years ago. Their data show that, although CO2 levels during glacials stayed well above the lows that occurred during the deep glacials of the past 800,000 years, the maximum CO2 concentrations during interglacials did not decline. The explanation for the change must therefore lie elsewhere.

Understanding what caused the shift in periodicity, known as the mid-Pleistocene transition (MPT), is one of the great challenges of palaeoclimate science. The 40,000-year periodicity that dominated until about 1 million years ago is easily explained, because the tilt of Earth’s spin axis relative to its orbit around the Sun varies between 22.1° and 24.5° with the same period. In other words, before the MPT, low tilts led to cooler summers that promoted the growth and preservation of ice sheets.

But after the MPT, glacial cycles lasted for two to three tilt cycles. Because the pattern of variation in Earth’s orbit and tilt remained unchanged, this implies that the energy needed to lose ice sheets2 had increased. One prominent explanation3 is that atmospheric levels of CO2 were declining, and eventually crossed a threshold value below which the net cooling effect of the decline allowed ice sheets to persist and grow larger.

Ancient air trapped in Antarctic ice can be extracted from cores drilled from the ice sheet, allowing the CO2 concentration to be measured directly, but the ice-core record extends to only 800,000 years ago4. Estimates of CO2 concentrations from earlier periods have been made by measuring the ratio of boron isotopes in shells found in ancient marine sediments5,6. This proxy measurement depends on a chemical equilibrium controlled by ocean acidity, which, in turn, is closely related to the atmospheric CO2 concentration.

But the estimates of CO2 levels inferred from such measurements are necessarily imprecise and must be verified using more-precise, direct measurements. Scientists have therefore formulated plans7 to find and retrieve deep ice cores that reach back to before the MPT (see go.nature.com/33mw4yk). One project has recently been funded by the European Union, and hopes to retrieve million-year-old ice in 2024.

Yan et al. tried another approach to finding similarly old ice, but nearer the surface of Antarctica. In regions known as blue-ice areas, the combination of ice flow against a mountain barrier and surface ice loss by wind scouring and sublimation (transformation of ice directly into water vapour) leads to upwelling of old ice towards the surface. The authors therefore studied two cores, 147 and 191 metres deep, that were drilled to bedrock in the blue-ice region near the Allan Hills in Antarctica (Fig. 1).

Figure 1 | Blue ice near the Allan Hills region of Antarctica. The environmental conditions in this area draw ancent ice to the surface. Yan et al.1 have analysed air trapped in an ice core drilled from this region to obtain the first direct measurements of atmospheric carbon dioxide levels from more than 1 million years ago.Credit: Sean Mackay

Figure 1 | Blue ice near the Allan Hills region of Antarctica. The environmental conditions in this area draw ancent ice to the surface. Yan et al.1 have analysed air trapped in an ice core drilled from this region to obtain the first direct measurements of atmospheric carbon dioxide levels from more than 1 million years ago.Credit: Sean Mackay

Full article here.

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76 thoughts on “Ancient Air Challenges Prominent Explanation For A Shift In Glacial Cycles

  1. I’m guessing that we don’t know how thick the northern ice sheets were a million years ago.

    Glaciation depends on water removed from the ocean. Evaporating the water removes heat from the ocean. Colder water holds more CO2, which is then removed from the atmosphere. The thicker the northern ice sheets, the more the CO2 removed from the atmosphere. This fits the fact that atmospheric CO2 lags temperature. link

    This link discusses how the closing of the Isthmus of Panama, between 5 and 1 million years ago, led to the modern glaciation regime.

    • The last paragraph on that linked page is revealing:

      The lessons from these vast geologic and geographic changes is both elegantly simple and excruciatingly complex. The opening and closing of seaways has a profound influence on the distribution of fresh water, nutrients, and energy in the global ocean. The coupling of these changing oceans with a changing atmosphere inevitably means a changing climate.

    • I’m guessing that we don’t know how thick the northern ice sheets were a million years ago

      Every glacial period has scoured the surface clean and destroyed most of the direct evidence of the previous glacials. It’s generally accepted that the pre-MPT glacials were much milder than the post-MPT glacials. I think this is mainly based on palaeotemperature estimates. Possibly some sea-level data to show how much water is trapped in the NH icecap.

      In view of the tunnel vision that characterizes modern climate science, it’s quite surprising that they admit “it’s not CO2, it must be something else” so readily. The Isthmus of Panama explanation for the latest glacial periods has been around for at least 40 years. It is quite convincing, but it’s been sidelined by climate science in favour of the “CO2 drives climate” explanation.

      Or it could simply be that the 30 million year global cooling trend reached a point where NH ice caps that started to form in the 41,000 year cycles finally got big enough to sustain themselves through a Milankovitch maximum, leading to the present “long glacials” regime.

      The “dust” explanation for the end of the recent “long” glacials is a possible. It also seems likely that lowering sea level by 120 metres could have altered ocean circulation patterns and reduced the snowfall needed to sustain the ice caps, and that could trigger irreversible melting, with or without the dust.

      Describing the glacial-interglacial alternation as a cyclic phenomenon may be a mis-characterization. If you look at temperature reconstructions, they form an asymmetrical saw-tooth pattern. It looks like cooling and icecap growth are the normal condition, but they reach a (dare I use the words?) tipping point where there is very rapid warming (and release of CO2 from the warming oceans) through a short melting phase. This returns the climate system to its “normal” cooling condition, and the earth drifts through a progressively cooling interglacial (which is where we are now) into the next glacial. And so on. No end in sight.

      Once you learn to accept that ocean temperatures control atmospheric CO2 levels*, it gets easier to look for other climate drivers than the demon gas.

      * with some assistance from fossil fuels in the late Holocene.

      • Didn’t you know that the CO2 levels in the soda bottle in your refrigerator control the temperature of not only the soda, but also the refrigerator itself? No grant money for you!

      • Totally agreed, Smart Rock.

        There is also no good reason that I have yet seen explained which justifies why different parts of the globe (specifically polar and equatorial latitudes) must necessarily warm or cool in synchrony.

        Warmer tropics and simultaneously cooler poles than today are not at all impossible, nor vice versa. There is no such thing as a global temperature.

  2. Lately I got ‘This page can not be reached’ when going here. When reloading I get a disturbed page two or three times before it show up. Only me or is it common Political disturbance ?

  3. Is the focus on CO₂ as a major factor for glaciation not a bit too tunnel visioned?
    What about the Sun’s radiation spectrum and intensity? I understand that we probably have no proxies for the Sun’s behavior so far back, and that funding studies of CO₂ comes easier.

    • The sense of impending doom is widespread. People have a shared delusion that they can DO something about CO2 so they focus on it like the drunk looking for his quarter under the streetlight even though he had dropped it elsewhere.

      • When the drunk at the bar, searches for his quarter, that rolled under a table, not realizing he dropped it at a different bar, yet finds a quarter, he is certain he was right all along and nothing can move him toward the truth.

        Look I found my CO2 under you table, dang its hot in here.

  4. The glacial cycle does appear to be driven by CO2, but not in the way that modellers want. The warm inter-glacials were caused by CO2 levels getting too low!

    See
    https://www.sciencedirect.com/science/article/pii/S1674987116300305

    Modulation of ice ages via precession and dust-albedo feedbacks
    We present here a simple and novel proposal for the modulation and rhythm of ice-ages and interglacials during the late Pleistocene. While the standard Milankovitch-precession theory fails to explain the long intervals between interglacials, these can be accounted for by a novel forcing and feedback system involving CO2, dust and albedo. During the glacial period, the high albedo of the northern ice sheets drives down global temperatures and CO2 concentrations, despite subsequent precessional forcing maxima. Over the following millennia more CO2 is sequestered in the oceans and atmospheric concentrations eventually reach a critical minima of about 200 ppm, which combined with arid conditions, causes a die-back of temperate and boreal forests and grasslands, especially at high altitude. The ensuing soil erosion generates dust storms, resulting in increased dust deposition and lower albedo on the northern ice sheets. As northern hemisphere insolation increases during the next Milankovitch cycle, the dust-laden ice-sheets absorb considerably more insolation and undergo rapid melting, which forces the climate into an interglacial period. The proposed mechanism is simple, robust, and comprehensive in its scope, and its key elements are well supported by empirical evidence.

      • The dust, as an albedo contributor, is probably not as important on top of the ice as it is to cloud formation. The dust particles give the water something to condense around. It is cloud albedo that matters most to glaciation flips, not ice albedo. Of course, lots of clouds tend to create larger amounts of deposition onto glaciers. But then they also cool the Earth on balance. When cloud cover based cooling leads to less energy for the convective pump over the long run, then there will be less cloud, less deposition, more sunny days, more melting. The dust can settle out of the atmosphere directly, or in rain or snow, and of course, we also have to factor in the aerosol cooling effects of the dust particles, too. Once the Earth begins to warm, ocean outgassing of CO2 provides more plant production, the Earth greens, dust removal from barren plains is slowed, leading to less dust, and less cloud nucleation, etc. All these things must factor in to the glacial / inter-glacial changeovers.

        To paraphrase talking Barbie, understanding Climate shifts is hard.

    • The problem with the dust deposition idea is the same as the black Carbon argument. After it is deposited, the next day or after comes more snow to cover it. It is not as if they are painting it black and it stays that way. The frost and snow quickly cover anything that falls.

      To me it is an idea that sounds possible only if you leave out other processes which are obvious if you go and look at the situation on the ground.

      What is the timing of the solar system passing through the arms of the galaxy?

      • Crispin, I think you misunderstand the scenario. The dust does get laid down and covered up over the 40K year ice age. However, when the initial melting starts due to the orbital changes the dust now starts to appear in the various layers of ice speeding up the melting over previous 40K year periods when there was no dust. The faster melting then allows enough ice to melt to push the planet into an interglacial.

        • Some dust makes the difference between two miles of ice accumulating over tens of thousands of years, and all two miles of it melting in a fraction of that time?
          Not buying it.
          Leaves far too much unexplained.
          Milankovitch cycles are also on somewhat shaky ground, IMO.
          Some of the ice age cycles match up with insolation at 65°N, but others do not, at all.
          And those cycles are gradual and continuous, but the pattern of glacials and interglacials is not.
          And what about length of the more recent cycles, all roughly similar?
          I am not sure about what the timing of passage through galactic arms is, but I think there is something happening not explained by the processes we are all familiar with. Something very cyclical.
          About the only thing that is clear is that CO2 lagging inflection points in the trends, time after time, and by hundreds of years, rules it out as a cause. And this is only one of several lines of evidence that all by themselves rule out “CO2 is thermostat of the planet” hypothesis.

        • Yes, Richard M, like in the city in the early spring when the snowbanks are just large piles of sand that was deposited by sander trucks and then plowed up between snowstorms. The dark sand quickly melts the rest of the pile, once the top layers of white are melted and the sand sinks down until there is only sand left. Spreading sand on any ice in your driveway will accelerate the melting as long as it is not shaded (it doesn’t need to contain salt). This definitely makes sense to me. The question is whether there is dust like that in the right parts of the ice cores? The claim that “its key elements are well supported by empirical evidence” would seem to imply that.

        • Melting ice does not make an inter-glacial; higher temperatures do.
          No need for dust to melt glaciers if you have higher temperatures already.

      • Crispin…

        The dust is laid down year after year for about 10 or 15 kyr before an interglacial, and that timing is explanatory.

        The 10 kyr of dust is waiting for an increase in precession (a NH Great Summer or NH precessional maximum), which can deliver high elevation (declination) insolation to the Arctic that can melt a layer or two of ice. As soon as it does so, the old dust in layers below concentrates on the surface and lowers the ice albedo, resulting in a powerful positive feedback agent, that gets more powerful annual year by annual year. As long as the precessional insolation during an annual summer is strong enough to melt the last annual winter snowfall, the process will continue. And the dust WILL stay there and concentrate on the surface, just as it does on the surface of our melting annual roadside snows.

        So an interglacial requires 10 kyr of dust, plus a strong Great Summer (precessional maximum).

        Thus the timing of the 10 to 15 ky of dust is determined by the precessional cycle. All recent interglacials were triggered by precession (not by obliquity as this paper says), and so the dust can only be laid down for a max of 15 kyr – or 3/4 of a precessional cycle.

        If the next precessional cycle is not strong enough to trigger an interglacial, then the north is plunged into another NH Great Winter (NH precessional minima), and the world waits for another 22 kyr for the next NH Great Summer (NH precessional maximum). The events will then repeat. The dust will naturally stop during the failed interglacial, because it is warmer and CO2 rises, and then start again for 10 kyr prior to the next NH Great Summer (dust is modulated by CO2)

        NOTE…….
        Post MPT interglacials are only triggered by NH Great Summers, meaning that the feedback mechanism is northern-centric, not global. In other words, the feedback agent CANNOT be global CO2 – it has to be something in the northern hemisphere – something like ice sheet albedo…

        Ralph

  5. Re: “…before the MPT, low tilts led to cooler summers that promoted the growth and preservation of ice sheets.”

    Not just cooler summers, but also warmer winters. Cooler summers melt ice sheets more slowly, and milder winters deposit more snow on them. The combination leads to advancing & thickening ice sheets and glaciers.

    Warmer air carries more moisture. Below freezing, it’s apparently 8-12% more moisture per each 1°C of warming! (That’s why heaviest blizzards occur when temperatures are only moderately below freezing.)
    http://web.gccaz.edu/~lnewman/gph111/topic_units/labs_all/water%20vapor%20capacity%20of%20air.pdf
    https://www.google.com/search?q=%22too+cold+to+snow%22

    Every climate alarmist has heard of “water vapor amplification,” which occurs for the same reason. Yet most of them have never heard that milder winters can result in more snowfall on ice sheets and glaciers, reducing sea-levels by increasing the amount of frozen water sequestered on land.

      • Salute!

        Whatever happened to the theory I recall from the 1950’s that postulated the glaciers grew because the Arctic was relatively ice free? Hence, more snow and eventually continental glaciers.

        This may have been in SciAm, but I have no archival access.

        Gums asks….

        • There could be some merit to glaciers growing (on Canada and Russia) during an ice-free Arctic.

          Even in today’s climate, snow tends to accumulate on the lee shores of the Great Lakes in late fall and early winter as cold air blows across the open lakes, absorbs evaporated moisture from the lakes, and deposits it as snow. As winter progresses and the lakes freeze over, there is little evaporation from the lakes, and cold fronts bring less snow late in the winter than earlier.

          We also see this trend in the Arctic. For example, the heaviest snowfall at Barrow, Alaska is in October, when there is still a large area of open water along the Arctic coast. As autumn progresses and Arctic sea ice reaches the coast, snowfall at Barrow decreases sharply, and is minimal for most of the winter.

          But what if the Arctic Ocean became warm enough in the summer to remain ice-free most of the winter? Could this cause enough increased snowfall over northern Canada and Russia that it wouldn’t all melt in summer, and start accumulating glaciers on land? Once the glaciers started growing, they would reflect incoming sunlight, and the climate over them would become colder, increasing the tendency toward further glaciation.

          If the Arctic Ocean had been ice-free in the past, it may not have anything to do with CO2. Several submarine expeditions under Arctic ice have discovered hot springs at the sea floor. If these springs flowed at higher rates in the past, they could have melted Arctic ice from below, and prevented it from re-freezing in winter.

          An Ice Age could also be reversed, due to a drop in sea level. The Bering Strait is not very deep, and could be closed by a land bridge during a sharp drop in sea level. This would prevent the mixing of cold Arctic water with warm Pacific water, resulting in the Arctic becoming colder and re-freezing, cutting off the supply of snow to the glaciers, while the warmer Pacific would bring rain to the edges of the glaciers, tending to melt them.

          Admittedly, a lot of this is speculation, but it is possible that an ice-free Artic could lead to glaciation over northern Canada and Russia.

    • I don’t see this being true, as the angle of obliquity has stayed remarkably consistent for the last 2.5 million years. The answer to the MPT conundrum does NOT lie in variations in obliquity.

      Ralph

      • Tilt angle is the most important Milankovitch cycle. Its 41,000-year cycle ruled glaciation during the early Pleistocene, and still operated in the late Pleistocene and Holocene.

  6. “This proxy measurement depends on a chemical equilibrium controlled by ocean acidity, which, in turn, is closely related to the atmospheric CO2 concentration.”

    This is just not a reliable assertion. At a time of much more undersea and terrestrial geological activity, ocean acidity would be less related to atmospheric CO2 than today, today, I suspect, and with good reasons, that atmospheric CO2 has an extremely small effect on ocean acidity, much akin to the sun in December having little effect on the temperature of you centrally heated home

    The fact there is for all intents and purposes, no data for this points out again, more crystal ball gazing.

    The proxies we use for millions of years ago, there are so many unknown factors so as to make such assertions mere guesses, educated guesses yes, but the uncertainty is enormous, so much so that any results must be taken with a shovel of salt.

    • “much akin to the sun in December having little effect on the temperature of you centrally heated home”

      When the sun shines into my south-facing windows in the fall and winter, my house gets nice and toasty.

      • Would you survive winter winter without any kind of extra heating than just the sun shining into your south-facing windows ?

        • Not in our local (Canada).
          But we have good windows, the double pane, argon gas filled ones, I imagine Jeff might have them as well.
          When the winter sun is low but shinning bright, we also get great heat from the windows so much so that we’ve had to crack open a window now and again.

  7. The cause of glaciation is a result of the rate of change in orbital eccentricity going negative. The annual cycle in TPW ends cup with cloud formation and ice deposition in the northern hemisphere overtaking the rate of ice melt so it accumulates:
    https://1drv.ms/b/s!Aq1iAj8Yo7jNg0ONoV86hmuEpHGt
    The black up arrows are indicative of the onset of glaciation give or take the accuracy of the ice core dating, the actual eccentricity rather than the rate of change and the axis tilt which alters the view sun has of the hemispheres.

    At present eccentricity the annual change in insolation is 22w/sq.m. That, combined with the high proportion of sea surface in the southern hemisphere and significant more land in the northern hemisphere, creates a dramatic change in water vapour in annual cycle. At present 2500Gt increase the decrease each year.

    This simple table demonstrates that nonsense of “greenhouse” gas:
    Mnth TPW- OLR
    Jan 17.04 236.8
    Feb 17.29 236.5
    Mar 17.73 237.9
    Apr 18.19 238.7
    May 20.40 240.6
    Jun 20.92 243
    Jul 21.89 243.9
    Aug 21.04 243.4
    Sep 20.54 242.2
    Oct 19.68 239.5
    Nov 18.93 237.1
    Dec 18.91 236.5

    Water vapour starts the year near its minimum when outgoing long wave radiation is also a minimum. By July the water vapour reaches its maximum when OLR also reaches its. So water vapour are giggly positively correlated. More water vapour results in more OLR; not by cause by via the influence of clouds, orbital eccentricity and distribution of water over the globe:
    https://1drv.ms/b/s!Aq1iAj8Yo7jNg0eoxeRHedx24wc5
    Withe a regression coefficient of 83% to the trend line, it is a good correlation.

    If climate models included orbital eccentricity, so-called climate scientists would not be making silly comments about “greenhouse” gasses.

    • Glad to find that I’m not the only person looking at humidity/water vapor as a factor.

      Higher water vapor levels will create more cloud masses, which increase albedo (reflecting sunlight) levels. Also produces more precipitation overall. Hmmmm…… earlier snow season starts, longer periods of spring rains interfering with planting and harvesting….. more rain at watershed heads increases risks of flooding downstream on all waterways, big and small, and higher lake levels whether it’s the Great Lakes or your local recreational fishing pond.

      Time to start putting out birdfood.

      • Sara
        Spot on-

        Clouds are twice as effective at cooling as they are at heating. Reflected SW v Clouds:
        https://1drv.ms/b/s!Aq1iAj8Yo7jNg0bl2B46ioIcDZ1C
        RSW increases by 3W/sq,m for every 1% increase in cloud.

        OLR v Cloud:
        https://1drv.ms/b/s!Aq1iAj8Yo7jNg0IRyDIi8vnTC1Gt
        OLR reduces by 1.5W/sq.m for every 1% increase in cloud. This is only half of what gets selected. Clouds cool the planet.

        Looking at the annual weather loop is enlightening:
        https://1drv.ms/b/s!Aq1iAj8Yo7jNg0pwm4INgP5FSBCu
        The interesting detail here is that sea surface temperature reaches a maximum in July or August. That is the water from land flows into the oceans. This image shows the increase in SST from just July to August:
        https://1drv.ms/u/s!Aq1iAj8Yo7jNg0lXWzyccVHItf34
        Note how the SST adjacent to the northern land masses and the enclosed water bodies increases dramatically in just one month.

        When the eccentricity moves to a reducing phase the TPW reduces year on year by just enough to start accumulating on land.

        We should be heading for glaciation now but we may not make it because eccentricity is relatively low and reducing, so negative phase, but the annual variation in insolation may not be enough to get the required variation in TPW to create glaciation. In 24kyr the eccentricity will be almost circular with just 3W/sq.m annual variation. The last time there was a minimum this low was 1.2Myr ago.

        Glaciation is an energy intensive process. In rapid glaciation, the sea level can fall 7mm/yr. That requires a huge amount of energy. I am not sure if 22W/sq.m, and reducing, is sufficient to initiate glaciation. Life on earth may not experience glaciation till the next negative phase; at least 100kyr away.

        • RickWill – November 4, 2019 at 4:24 am

          Glaciation is an energy intensive process. In rapid glaciation, the sea level can fall 7mm/yr. That requires a huge amount of energy.

          Seems to me you are “thinking” commercial/domestic refrigeration ……. but talking natural glaciation.

          In actuality, the sea level falls FAR MORE THAN 7mm/yr, …… but the rain water and snow melt is constantly flowing back into the ocean ….. which negates an actual measurement of any “sea level fall”.

          Even during periods of glaciation, ….. the tropics has to provide the H20 vapor for creating the snowfall required for glacier “building” in the norther/southern latitudes and high mountain ranges.

          • During glaciation the typical fall in sea level is 120m. During the peak periods of ice accumulation, the sea level can fall 70m in 10kyr. That averages at 7mm/yr loss in sea level. Evaporating water from the ocean and depositing on land IS energy intensive.

            During the depth of glaciation to interglacial occurs in less than 10kyr with sea level rising 120m. Melting ice requires 1/5th the energy of evaporating the water from the ocean to form it. So it is to be expected that the melt phase would be far more rapid than the deposition phase.

          • Melting ice requires 1/5th the energy of evaporating the water from the ocean to form it. So it is to be expected that the melt phase would be far more rapid than the deposition phase.

            Who cares, other than you,

            That was a delusional statement. The energy needed for evaporation (phase change) of liquid water to a gas ….. is released when the gas changes back to liquid water droplets.

            When the liquid water droplets release additional energy a phase change to ice/snow occurs. When snow/ice undergoes a phase change to liquid (evaporation) or a gas (sublimation) energy is absorbed.

      • RickWill: To be frank, I expect to see more flooding on the Mississippi River from now on. The Missouri River empties into the Mississippie River, as do others like the Wisconsin River and the Des Plaines River.

        The Des Plaines River literally overflowed its banks in September and has not gone down yet. It has a very deep channel to follow, and this flooding syndrome started in 2004.

        Lake Michigan is reported to be 11 inches higher than its normal levels, producing some bodacious surf shots along the lake shore, and is projected to be another 33 inches higher than normal in the near future. I don’t know about the other Great Lakes. ALL the catchment basins in my area are full and are not going down.

        I expect to see more of it, too. It would be nice if someone started a survey of this kind of thing. It is not going away any time soon. We could at least prepare for it.

        • ALL the catchment basins in my area are full and are not going down.

          Catchment basins (dams & reservoirs, etc.) that are under the supervision of the Army Corps of Eng. usually remain at “summer pool” level until after Thanksgiving week, ….. then they start reducing their level to “winter pool” requirement in preparation for winter/spring flooding events.

    • Eccentricity has a cycle of approx 100,000 years. The Earth is at a 400,000 year low eccentricity which the past has indicated a longer interglacial. We have a ways to go yet and none of us will be alive when this interglacial ends. So no worries.

    • RickWill – November 4, 2019 at 2:14 am

      Water vapour starts the year near its minimum

      Is that “starts the year” near its minimum in the Northern Hemisphere or in the Southern Hemisphere?

      Or is that “starts the year” near its minimum in southern California or in northern New York?

      Or is that “starts the year” near its minimum in Alaska or in Australia?

      Or is it in the equatorial tropics where water vapour starts the year near its maximum (4%)?

      • The TPW in charts are globally. No cherry picked data here. It happens every year. The water vapour in the atmosphere reaches its minimum each year at the start of the calendar year. It rise to its peak in July and then begins to fall.

    • Eccentricity has absolutely NO effect of the total insolation impacting the Earth.

      The only reason eccentricity appears to have an effect, is that it strengthens the effects of precession, and it is precession that is the key forcing agent during the past-MOT era.

      Ralph

      • Eccentricity causes a massive variation in the annual variation and also the long term average.

        At peak orbital eccentricity the annual variation in insolation is 50W/sq.m. At minimum eccentricity it drops to a range of 3W/sq.m. At present time we are 24kry from a minimum eccentricity but the annual range in insolation is still 22W/sq.m. That variation, combined with the sun’s focus being on the Southern Hemisphere when at peak insolation, increases the global atmospheric water column by 5mm, which is 2500Gt of water to the atmosphere.

        The difference in annual average insolation between peak eccentricity to minimum eccentricity is 4.5W/sq.m, being lowest when it is near a circular orbit.

        • Eccentricity does NOT cause insolation variation.
          Eccentricity merely energises the insolation variation caused by precession.
          Big difference.

          And Eccentricity does not energise the insolation variation caused by obliquity.
          Which is important.

          Ralph

          • Insolation is defdined as the solar radiation reaching a given area.

            Perihelion in 2020 will be on Jan 5 with earth 0.9832436AU from the sun. The insolation reaching earth on that day will be 1407W/sq.m. for surface normal to the rays. Aphelion occurs Jul 4 when earth is 1.0166943AU from the sun. The insolation on that day will be 1317W/sq.m.
            http://www.astropixels.com/ephemeris/perap2001.html

            The difference in insolation at top of the atmosphere next year, normal to sun rays, is 85W/sq.m, which becomes 21W/sq.m when average over the top of the atmosphere.

      • How could eccentricity not affect insulation strength?

        When Earth is closer to the Sun, it receives more radiation. When farther away, less. I’d have thought that fact to be obvious.

        Since our orbit is fairly circular, the difference is not as great as for Mars or Mercury, but still significant.

  8. OK what is needed to settle this confusion regarding what introduced the change in glaciation periodicity is someone who can see CO2 with their own eyes.!
    Bring on, Greta TinTin Eleonora Ernman Thunberg. What her parents lacked in common sense they certainly made up for in imagination, and passed on that attribute to dear Greta.
    I am in the changing ocean currents due to plate tectonic activity, but plenty of scope for investigation. I am also certain it has nothing to do with CO2 .

  9. Simply looking at charts of temperature vs. CO2 levels over a few interglacial periods shows CO2 levels at their highest just prior to reglaciating. Therefore, how can CO2 drive the interglacial periods? Makes no sense. Then consider that CO2 level changes after temperature changes. CO2 driving temperature isn’t even wrong as some may say.

    • Or, it may be CO2’s warming effect saturates around 200 ppm. Hence, any values above that provide little warming influence.

      I found this comment in an old blog from physicist RGB

      “It is reasonable to expect that broading due to doubling from q = 0.0003 to q = 0.0006 would have no more than a 0.001 relative effect on the total atmospheric absorptivity computed — almost certainly completely negligible”

      This comment makes me wonder if the assumed CO2 warming effect of ~1 C / doubling is not overstated at current concentrations. If pressure broadening has only a negligible effect then climate sensitivity may be far less than any of us have assumed.

    • I wouldn’t say that human evolution accelerated a million years ago. The changes in H. erectus and its closest relatives were gradual. The not universally accepted “species” H. antecessor spanned 1.2 million to 800,000 years ago, but is often considered simply a late western variant of H. erectus.

      From about 700,000 years ago, however, H. heidelbergensis does start to show more modern traits. By 300,000 years ago, it was regionally evolving into Neanderthals, Denisovans and Anatomical Moderns, plus some other local variants.

  10. The MPT (from predominantly obliquity influences to predominantly precessional influences) was caused by Antarctica becoming fully glaciated.

    Prior to the MPT Antarctica and the Arctic both had fluctuating ice sheets, so the precessional fluctuations in ice sheets cancel themselves out, leaving just the influences of obliquity periodicity. After the MPT Antarctica was permanently fully glaciated, and so the precessional fluctuations in the Arctic can then show up in the record. And since precessional effects are stronger than obliquity, the periodicity of precession became dominant.

    Remember that the paleoclimatic ice record is effectively a record of sea level variations, so it is the sum of precession and obliquity. This record cannot separate precessional and obliquity effects – it cannot tell if Arctic precession is being cancelled out by Antarctic precession.

    Note…
    Precession operates alternately in each hemisphere.
    Obliquity operates simultaneously in both hemispheres.
    So precession can cancel itself out, while obliquity cannot….

    Ralph

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

    Yes Ralf has his dust hypothesis which has some evidence to support it and would be more persuasive if it was not mixed with unnecessary denial of Milankovitch cycles. Every one of the 30 or so interglacials in the Pleistocene have occurred 6500 years after an obliquity peak, showing ocean heating of obliquity with the expected thermal lag (how long it takes to move ocean temperatures). What are the chances of all those 30 coincidences? Here are the post MPR interglacials plotted with 6500-year lagged obliquity (thanks to Javier):

    https://m.imgur.com/gallery/fI1uUqZ

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

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

    IQ tests principally test one’s ability to see a pattern or trend and extrapolate it forward. Looking at this trend of slowing down flickering between two attractors, what comes next? Anyone?

    Yes, well done 👍. The flickering stops and we enter permanent deep glaciation.

    All this can be summed up in 3 words. Winter is coming. Enjoy.

  12. The 41,000-year tilt cycle didn’t end at the Mid-Pleistocene Transition. What seems to have happened is that an increasingly cold world caused every other or every third interglacial to be stillborn, becoming interstadials within glacials, rather than fullblown interglacials.

    Thus the apparent ~100,000-year glacials of the late Pleistocene could result from an average of 82,000- and 123,000-year-long glacials. Besides greater average cold as the Pleistocene wore on, other Milankovitch cycles may modulate the strength of interglacials. Dust might also play a part, with more of it produced due to deeper and longer glacials.

    • For instance, the most recent, Wisconsin glaciation can be seen as two 41,000-year tilt cycles, ie MIS 2 and 4, separated by an aborted cycle or cold interglacial, ie MIS 3. The latter stages of MIS 5, which began with the Eemian Interglacial, also used to be included in the Wisconsin, but it’s now often supposed to start with MIS 4, only some 71 Ka, rather than ~114 Ka.

      http://www.skb.com/publication/2677502/TR-13-02.pdf

      Marine Isotope Stages don’t always correspond with epoch and age boundaries, as is the case with the Holocene, ie ~11.4 Ka v. MIS 1, ~14 Ka.

  13. In a normal world, most of us would look at this and conclude that CO2 cannot possibly be the culprit. Major temperature changes happened with the same CO2 levels. It got colder when there was more CO2 in the air and it got warmer when CO2 was at historic lows. And the movements of our planet through pace provide an explanation that adds up. Whats to discuss? Except that – the climate fanatics won’t have any of it. Facts are meaningless to them – only dogma counts.

    • >Whats to discuss?
      why did the glaciers melt from the last glaciation? Maybe 40 days and 40 nights of rain from an atmospheric river event?

      • The NH ice sheets melted after the last glacial maximum for the same reason they did so during the previous 2.6 million years. And it took longer than 40 days. About 10,000 years, in fact.

  14. Guesswork. The whole debate over climate change is based on guesswork. Don’t you people have something useful to do?

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