Sea levels, atmospheric pressure and land temperature during glacial maxima

by Alan Cannell

The new tropical lands: a carbon sink during formation and huge source of carbon dioxide and methane when lost to the sea.

  1. Why do Sea Level Changes Always Stop at about the Same Heights?

Sea water levels in the Red Sea (Hannish Sill) shows that these have risen and fallen between two extremes many times over the past 500ky (1). Slow cooling leads to a glacial minimum at about -120m below the present level, rapid warming to a new equilibrium at around current values. The question is not so much why these cycles occur, but why do they stop at these depths?

The answer seems to lie in the geography of the shallow seas and continental shelves that lie between latitudes +30 and -30. This is the zone of the trade winds where most water vapor evaporation takes place and is also the zone where, with the rise and fall of the seas, large tracts of land emerge and then sink again below the waves.

The largest of these areas is Sunda, the land exposed during glacial periods between S.E. Asia and Australia. A 1000 km cross section from the hills on the east Thai coast directly east to the Spartly islands shows that most of this area lies at less than 100 m below current sea level: at the coast, the land rises steeply, beyond the continental shelf, at about -120m, the sea floor drops off sharply.

This is fairly typical for most of the Sunda area so figure 2 can also be taken to roughly represent height (h) to Surface Area (SA).

Fig. 1 Cross Section E-W of the Sunda Plateau (latitude 8 degrees N) in km against Height above Present Sea level

In other words, the rate of change in sea Surface Area (dSA) per change in height (dh) goes from close to zero, to a maximum then back to around zero. Sathiamurthy and Voris (2) have estimated this rate for 10m intervals for the entire Sunda zone and, as shown below in Figure 2, the change in SA in km2 per change in 10m (dSA/dh) goes from some 160,000 km2 in new sea area as the level rises from zero to +10 m, to a maximum of 250-350,000 km2 between -10 and -60 m and then falls back to 30,000 km2 at -110 m to -116 m.

Fig. 2 Change in Land Surface Area per Change in Sea level

Water vapor is the most potent greenhouse gas and changes in sea level form a feedback process: when warming is taking place the ice caps melt and new areas of warm tropical seas are added that will increase water vapor in the air through evaporation; when cooling is taking place there is transfer of vapor (as snow) to the ice sheets, which stops when no significant new dry land is gained by a further drop in sea level along the continental shelves. If we assume evaporation (E) in the tropics to be proportional to SA, then dE/dh follows the same pattern. Equilibrium sea levels are reached when:

dE/dh0

With Google Earth it is possible to estimate the major areas within the tropics/sub-tropics affected by glacial sea level changes, using the -120 m contour as a guide, as shown in Table 1.

When islands are taken into consideration, the total tropical/sub-tropical land area exposed during a glacial minimum sea level can be taken as around 9 million km2. Virtually all of these major coastal shelves follow a similar pattern of rapid drop-off around -120m and a sharply elevating coastline at the present sea level, so a painstaking analysis of all land between of 0-10 m would reveal a similar pattern to that shown in Figure 2 for Sunda. Thus the highly complex interrelation of ice, sea and land follows a very simple equation: when dSA/dh is at a minimum the feedback process stops and this is reached when sea level is at the present or at -120 m ( 120 m below present sea-level).

Table 1. Tropical and Sub-Tropical Lands Revealed by Sea Level at -120 m

 

  1. Atmospheric Pressure and Temperature in Glacial Eras

At low sea stands the world is a very different place: although parts of today’s temperate zones were under ice, whole new areas appeared in the tropics. Total land and sea areas (km2) between latitudes 30N and 30S are shown in Table 2.

Table 2. Surface Areas in km2 between 30 Degrees (N and S) Present Sea Level and Glacial (-120 m)

At Glacial Maximums the land area is thus increased by 3.5% and thus the difference between present and glacial land and sea areas thus changes by 7%. This not only has an enormous effect on the evaporation of water vapor, but also affects the overall air pressure levels over ‘dry’ land.

The original research into glacial era air pressure was carried out by Marie-Antoinette Mélières in 1991 (3) which looked at the changes in atmospheric mass. This paper makes a series of assumptions in order to arrive at the conclusion that pressure was approximately unchanged. However, some of these assumptions are not true, in particular: a) that land area remains constant and b) that the question is not related to a fixed reference point on present dry land (which is effectively uplifted above sea-level).

                2.1 Air Sequestration

Ice caps not only lock away water as they develop in area and depth, they also entrap air. Freshly fallen snow is composed of about 70% air by volume and compacted snow (firn) about 50%. At Byrd Station, Antarctica, this firn transforms into ice at about 56 m depth with a gradual ‘close-off’ of porosity. The ice at this stage “contains approximately 10 per cent air by volume in the form of discrete bubbles.” (4). At this point this air is effectively removed from atmospheric circulation. These bubbles are reduced in size as internal pressure increases until in the deeper and bubble-free ice below 1200 m air entrapment ceases to be in bubble form and the gas molecules are dissolved in the ice as hydrates (5).

Under present-day climatic conditions, the air content of polar ice generally shows a high sensitivity to the atmospheric pressure and hence to the surface elevation of the ice sheet where the ice is formed (6). There is also a high variability in samples with higher average air content taken from Alaska, which may reflect that the effective pore close-off happens at a shallower depth. (In this case, insolation may be a factor that leads to the formation of ‘lids’ in layers with high air density, thus trapping the air below) (7).

When sea levels dropped by 120m over 70% of the surface of the earth, this water was locked into the ice caps, hence the volume of this new ice on land (specific density of ice/firn = 0.9) would have been around:

Surface of the Earth (SE)* 120m* 0.7/0.9 = SE*93 m3

This ice built up over land masses and continental shelves at lower heights; hence the air volume was slightly higher than the 10% formed at altitudes of 3000 m on the Antarctic and Greenland ice caps (where most ice-core drilling has taken place). Based on Alaskan samples this air represents some 12-13% at a close-off pressure of some 1.2 atmospheres. Thus the volume of trapped air would be 12-13%*1.2 or some 15% of this volume:

SE*93*0.15 = SE *14 m

To this must be added the air sequestered in the extensive marine and marine-grounded ice which did not cause a drop in sea level. This has been considered to be about 50% of the land ice. Hence the ‘removal’ of a ‘layer’ of air which when corrected for sea level at 1 bar is the equivalent of a drop in atmospheric pressure of some 20 m. 

             2.2 Isostatic Deformation

Although the volume of closed-off ice is very similar to the volume of water ‘lost’ from the sea, the concentration of land ice in very thick deposits had a significant isostatic effect on these land areas, forcing the land – through elastic and viscous mantle flow – to deform and sink. During a maximum glacial event, about one fifth of the SE was under ice – about two thirds of this over land or marine grounded. Taking 100 m as a working estimate for average deformation, this volume had to be filled with air molecules causing a further drop in global atmospheric pressure. At 1bar, this is equivalent to an altitude of about 10 m.

           2.3 Water Vapour and Air Pressure

Dry air is denser than moist air in the present climate. However, when there is a massive global reduction in water gas molecules (as more dry land is exposed and vapor trapped in ice), overall atmospheric pressure drops.

The first cause of this decrease in water vapor is due to the fall in surface sea temperatures (SST) which lowers the value for saturation of water in air. SST levels fell by some 3-5 C over the latitudes +30 to -30 thus saturation fell from around 1.8% (at 21C) to 1.6% (at 16C): a decline of 11% (8, 9).

The second reduction is due to the overall global dry conditions as vapor is locked away as ice, more land exposed and less tropical sea areas exposed to evaporation. An approximation of this effect has been made of an extra decline of 20%. Thus if the average number of water gas molecules presently in the atmosphere is about 2% (NASA), the total drop in water molecules in the atmosphere during glacial periods would be about 11%(SST)+ 20% (Dryness)=31%. At a density of 0.804 g/l (in comparison with that of dry air at 1.27 g/l at STP), this is equivalent to a loss of atmospheric pressure of 2%*0.31* 0.804/1.27 = 0.4%. This is equivalent to an elevation of about 45m. Dr Mélières presents a lower figure of about 1hPa, the equivalent of 10m (3).

         2.4 Lower Sea Levels = Lower Air Pressure over Present Day Landmasses and increases Thermal Feedback

During the stable glacial maximums, the present day coastlines were 120 m above sea level. Thus the drop in air pressure over present land expressed in equivalent present day height above sea level would be:

  • 120 m (drop in sea level) +
  • 20 m (air sequestration) +
  • 10 m (glacial deformation) +
  • 45 m (loss of gaseous water)

=195 m.

For cold, dry air, this drop in pressure signifies a drop in temperature of about 2 degrees Celsius.

This process also has a feedback effect:

  • as cooling starts, ice caps develop → air sequestered
  • sea levels drop → ice loading → deformation
  • reduction in gaseous water → resulting drop in air pressure
  • lower air pressure→ further cooling, etc.

The reverse is also true: during a warming event, ice melts and releases air and sea levels rise, all leading to even more warming.

  1. Carbon: Slowly Taken Out During Cooling and Rapidly Pumped Back During Warming

With sea levels at -120 m, most of the new dry land exposed between +/-30 degrees latitude would have been gradually ‘colonized’ by neighboring tropical forests, first by swamps and then after desalinization by fully developed forests. Some of these areas would be debatable, however, the Persian Gulf lands would be part of the Mesopotamian delta and the Red Sea was probably within the ‘green’ Sahara belt and would be lush rather than deserts. Other Continental Shelves may have been savannahs, however, most of the lands in the Gulf of Mexico were close to Florida, Yucutan and Vera Cruz.

An evaluation of several studies has shown that Equatorial Tropical Forest contains about 200 tons of carbon per hectare (10); this also being the value quoted by the IPCC (2006). More recent studies analyzing the diversity of tree species in relation to total carbon (11) have confirmed these values, although in South America the value is slightly lower, possibly due to large tree removal in the recent past.

The process of forest growth would have been slow as, meter by meter, land was reclaimed from the sea. Although present land would be getting progressively cooler as air pressure dropped, this new land would still have been mainly tropical: Figure 3 shows the Atlantic Rain Forest in Southern Brazil flourishing at 800 m, 5 to 6 C cooler than at sea-level and subject to winter frosts.

Fig. 3 Atlantic Rain Forest at Altitude

Eventually about 150 billion tonnes of carbon would be fixed in these new forests, along with the carbon fixed in the soil – estimated at about 50 tonnes/ha for low tropical altitudes (12). This totals close on 221 billion tonnes of carbon, or approximately the equivalent of 650 billion tonnes of CO2. The present mass of carbon dioxide is given as 3200 billion tonnes, so taking the mass of atmospheric CO2 during MIS 3 to be around 2000 billion tonnes, this CO2 capture in the new lands at low level is of the order of 25 to 30% of the available CO2 in the atmosphere. Again we may assume a feedback process: as more carbon is sequestered by the new forests there would be more gradual cooling.

The reverse is slightly different: once the globe starts to warms and sea levels start to rise rapidly at about 2 m per century, these forests would first die-off as salt water reaches the roots, then be partly submerged in tidal sea water and subjected to wave action – during this time the dead wood would have been eaten by fungi in aerobic conditions and producing mainly CO2. Final breakdown would have taken place by the action of worms, shellfish, bacteria, etc., releasing vast amounts of stored carbon in the form of CO2 and methane.

The resulting beaches, mud flats and sand dunes would in turn be gradually submerged and it is assumed that the residual carbon in these drowned biomes would have been low, as sand dunes only have a carbon content of about 3.6 tonnes/ha (13). The main difference between the colonization of reclaimed lands and their loss by sea rise is, of course, the rate at which it happens. Forests rot much faster than they grow and a tropical/subtropical area the size of Brazil would have been submerged in just a few thousand years. This hypothesis (and we can take as given that there were vast new lands, vast new tropical forests and a rapid loss of nearly all the carbon at the start of the Holocene) implies a lapse of several hundred years between temperature (and sea-level) rise, and the final release of the stored carbon. Again this is a much quoted point of discussion and the author hopes that further work on the rate of carbon released (roughly equivalent to the surface area inundated over time) may correlate with the Warming Pulse 1A.

References [references ]

addl ref added:

Leite et al, Forest expansion during the last glacial period 
.
Biosketch: Alan Cannell, Anglo-Brazilian Engineer (Urban Design and Transport), Member of the Italian Institute of Human Paleontology (ISIPU).  Objective is to examine questions related to Paleoanthropology from an engineering point-of-view, highlighting topics that may have been overlooked yet interest the professionals.

Moderation note:  As with all guest posts, please keep your comments civil and relevant.

 

84 responses to “Sea levels, atmospheric pressure and land temperature during glacial maxima

  1. David L. Hagen (HagenDL)

    For a standard atmospheric lapse rate of 6.49 deg C/km, the 195 m change would be equivalent to 1.27 deg C.
    https://www.ivao.aero/training/documentation/books/Student_ISA.pdf

  2. Interesting, but some of it doesn’t seem quite right – I’ll need to think about it a bit more. But, for example …
    – “Taking 100 m as a working estimate for average deformation, this volume had to be filled with air molecules causing a further drop in global atmospheric pressure.” – I don’t see why the land dropping should cause a drop in atmospheric pressure; the same surface area is under the same air volume. Maybe the whole atmosphere just drops a bit, rather than expanding to keep the TOA at the same place?
    – “Forests rot much faster than they grow and a tropical/subtropical area the size of Brazil would have been submerged in just a few thousand years.” – Is this really so? A few thousand years to be submerged and rot is surely far more time than would be needed for a forest to grow??

    • I am also skeptical that forests rot much faster than they grow. In anaerobic marsh conditions, logs can last a very long time.

      • Alan Cannell

        Mike
        Any patm difference due to glacial deformation (isostatic) would have been minimal – as I believe I point out. This was only included as the topic was discussed in the original paper by Marie.
        The question is the effect of salt water: first killing trees when the roots are reached, then the wave action and sea marine life.
        For the major forests of the temperate zones to develop the land first has to de-iced, then warmed, then colonized bit-by-bit, then mature over many hundreds of years. I suspect that this would take longer than losing all the tropical forests, but this Drowned Forest Effect needs further work.

  3. Alan Cannell,

    Thank you for this interesting post.

    Slow cooling leads to a glacial minimum at about -120m below the present level, rapid warming to a new equilibrium at around current values. The question is not so much why these cycles occur, but why do they stop at these depths?

    I suggest the answer to this question might be that the glacial cycles are roughly the same time span (82 ka to 123 ka, or roughly 100 ka); GMST declines for about 80 ka, rises over about 10 ka, and interglacial is about 10 ka. GMST has declined by about the same amount over the cooling period and risen about the same amount over the warming period in each glacial cycle over the last 500 ka. So, roughly the same amount of water is held in ice at each glacial maximum, and similarly at each glacial minimum. Therefore, the sea level range is roughly similar in each of the glacial cycles. Much more water was tied up in ice during Snowball Earth periods, than now, and much less when there was no polar ice sheets (which was the case for ~75% of the past 500 Ma).

    Leaving this aside, I am interested in your comments about the amount of carbon tied up in the biosphere during glacial versus interglacial times. IPCC AR4 WG1 Chapter 6 says there is about 50% more carbon tied up in the biosphere now than at the LGM. Is this consistent with what you are saying?

    I understand that during the Eocene Thermal Optimum, 50 Ma ago, GMST was about 11 C warmer than present, and average temperature of tropical seas was about 6 C warmer than at present. Tropical rain forests extended from pole to pole. Crocodiles and frost intolerant vegetation, such as palm trees, existed in the polar regions. That indicates no frosts even during 6 months of night. The mass of carbon tied up in the biosphere was some 5 times higher than now. CO2 concentrations in the atmosphere was about 1000 ppm.

    Source: https://www.nature.com/articles/ncomms14845#f1

    These conditions suggest that, during the Eocene Thermal Maximum,
    • sea levels were high (no ice caps),
    • CO2 concentration was high (~1000 ppm), and
    • the mass of carbon tied up in the biosphere was ~5 times higher than now.

    Can the high CO2 concentration and high mass of carbon in the biosphere be explained?

    Is the answer that the mass of C in the oceans and in carbonate deposits in the oceans reduced?

    • >Can the high CO2 concentration and high mass of carbon in the biosphere be explained?
      >Is the answer that the mass of C in the oceans and in carbonate deposits in the oceans reduced?

      Part of the answer is that evergreen forests are in carbon balance with the atmosphere and don’t sequester carbon in soils, so a pole to pole tropical forest would have removed almost all the carbon in the soils.

      • But vegetating gets its carbon from CO2 in the atmosphere, not from the soils. They drop litter which increases the mass of carbon on the forest floor and in the soils. There is much more carbon in the biosphere in warm climates than in cold climates.

        Furthermore, as GMST declines, the planet gets drier, forests give way to grasslands then to deserts. The amount of carbon in the biosphere decreases.

        So the high concentration of CO2 in the atmosphere and the 5 times higher mass of carbon in the biosphere during the ETM (50 Ma ago) must have come from somewhere. I suggest it is now dissolved in the oceans and tied up in carbonate deposits.

    • One of the other things that gives me cause to doubt this article is that it concentrates largely on atmospheric CO2 and the biomass. Patrick Moore provides context, and to my mind opens up different ways of thinking:

      “Let’s look at where all the carbon is in the world, and how it is moving around.
      Today, at just over 400 ppm, there are 850 billion tons of carbon as CO2 in the atmosphere. By comparison, when modern life-forms evolved over 500 million years ago there was nearly 15,000 billion tons of carbon in the atmosphere, 17 times today’s level. Plants and soils combined contain more than 2,000 billion tons of carbon, more that twice as much as the entire global atmosphere. The oceans contain 38,000 billion tons of carbon, as dissolved CO2, 45 times as much as in the atmosphere. Fossil fuels, which are made from plants that pulled CO2 from the atmosphere account for 5,000 – 10,000 billion tons of carbon, 6 – 12 times as much carbon as is in the atmosphere.

      But the truly stunning number is the amount of carbon that has been sequestered from the atmosphere and turned into carbonaceous rocks. 100,000,000 billion tons, that’s one quadrillion tons of carbon, have been turned into stone by marine species that learned to make armour-plating for themselves by combining calcium and carbon into calcium carbonate. Limestone, chalk, and marble are all of life origin and amount to 99.9% of all the carbon ever present in the global atmosphere. The white cliffs of Dover are made of the calcium carbonate skeletons of coccolithophores, tiny marine phytoplankton.

      The vast majority of the carbon dioxide that originated in the atmosphere has been sequestered and stored quite permanently in carbonaceous rocks where it cannot be used as food by plants.”
      https://www.thegwpf.org/patrick-moore-should-we-celebrate-carbon-dioxide/

      • Mike Jonas,

        Can you tell me where Patrick Moore got the 15,000 Gt C in the atmosphere 500 Ma ago?

        Today, at just over 400 ppm, there are 850 billion tons of carbon as CO2 in the atmosphere. By comparison, when modern life-forms evolved over 500 million years ago there was nearly 15,000 billion tons of carbon in the atmosphere, 17 times today’s level.

        The 15,000 Gt C doesn’t seem right to me. The Ediacarans were the first complex animal life and the first that could move. They began during the last snowball Earth period, about 620 Ma. This was colder than present, so CO2 concentrations would have been less than in the much warmer Cambrian period that followed. During the Cambrian explosion (of life), CO2 concentrations were around 2000 ppm, i.e. about 5 times higher than present. This seems at odds with the “17 times today’s level” quoted from Patrick Moore.

      • @ Mike Jonas:
        “But the truly stunning number is the amount of carbon that has been sequestered from the atmosphere and turned into carbonaceous rocks. 100,000,000 billion tons, that’s one quadrillion tons of carbon, have been turned into stone by marine species that learned to make armour-plating for themselves by combining calcium and carbon into calcium carbonate.”

        Minor terminology fix: These are the Carbonate rocks: Limestone, dolomite and the whole family. And yes, they dominate CO2 storage in the crust, just as you say.

  4. Why do Sea Level Changes Always Stop at about the Same Heights?

    They don’t. The first figure that should be there is a sea level reconstruction. There are several. For example Spratt et al., 2016.

    In general sea level is proportional to temperature. The question is: why does the planet stops warming and cooling where it does?

    The answer is primarily due to orbital conditions. Interglacials are warmer or cooler depending on orbital configuration. Melting the polar ice-sheets isn’t trivial as the more North the melting gets, the harder it is to further melt the ice-sheets, as the yearly energy received from the Sun falls fast. That’s why polar ice is so resilient and that is why sea levels don’t go much above present.

    On the other side you have a similar limit. Obliquity decrease takes insolation from high latitudes and puts it in the tropics, so as the ice advances South, the tropics receive more energy from the Sun. So it becomes more and more difficult to extend the ice-sheets South as the energy increase is higher and higher. This puts a limit to how cold the planet can get, and it limits also how low the sea-level can get.

    Another factor is that as continental ice-sheets grow they become more unstable. When they reach a size equivalent to a 120-m sea-level drop they are so unstable that the next high obliquity period will cause them to collapse producing an interglacial. This is Didier Paillard’s hypothesis from 1998 (Nature 391, 378), that is generally accepted, as it explains why after ice-sheets become that large an interglacial follows.

    • Javier, Thank you. Yours is a much clearer explanation than mine above.

    • Javier: “Obliquity decrease takes insolation from high latitudes and puts it in the tropics, so as the ice advances South, the tropics receive more energy from the Sun.”

      WR: to add: Colder conditions also result in less water vapor in the air. Following simple logic: less water vapor results in less clouds also over the tropics that enhance the effect of the higher tropical insolation. Extra absorption of sun energy by the oceans will constrain the slowing down of sea surface temperatures. A balancing mechanism, reacting on the change in orbital circumstances.

    • The answer is primarily due to orbital conditions. Interglacials are warmer or cooler depending on orbital configuration.

      This totally ignores internal factors. Sequestered ice on land flows and thaws and cools by reflecting and thawing. The orbital conditions repeated the same cycles over and over over during the most recent fifty million years while the bounds of glacials and interglacials got colder and colder. These cycles maxed over the most recent million years and max cycles ended after we came out of the last major cold period twenty thousand years ago. Warming stopped at a lower upper bound and colder cycles have stopped at warmer colder bounds for ten thousand years now.

      Understand ice core data and history and you can start to understand climate cycles. Ice extent cycles are causes of and not results of warming and cooling cycles.

      Open Arctic Oceans are required to produce evaporation and snowfall to build the ice on Greenland and other cold places in the Northern Hemisphere. Lake effect snow comes from thawed lakes and ocean effect snow comes from thawed oceans.

      Continental ice-sheets grow as new snow falls and as sequestered ice advances. Sea levels drop as long as ocean evaporation can produce more snowfall than thawing and flowing back into to the oceans produce. When the oceans are low enough and depleted of thawed water for evaporation in cold places, thawing exceeds accumulation from snowfall and the ocean drop stops. Whenever this happens, it will correlate with some orbital cycle, which will get credit for the lack of evaporation and snowfall.

      Ice ages occur because it snows too much when oceans are high and warm and thawed. Ice ages end because it snows too little when oceans are low and cold and frozen. These ice cycles are normal, natural and necessary. Look at ice core data and history.

      Alex Pope

  5. Hi Javier
    A check on the sea levels over the past several glacial cycles (500ka) given in the ref) shows that sea levels actually do stop at around 0 and 120m. The warming and cooling are processes that are based on the Milankovitch cycles, but with feedback mechanisms that stop the process at the stated levels. Topography is involved and this appears to relate to evaporation (water vapour) being a main driving force.

    David
    I assume that colder and drier air with less water vapoiur (higher density) would have a slightly higher T gradient, thus the 195m estimate would be closer to 2 C. This is often overlooked: for example, reconstructions of the forest temperatures in S Brazil have shown that Ts were some 5-7 C cooler OVER PRESENT LAND. Taking the exposed coastline of -100-120 m, we can reduce this to around 3-5 C – the equivalent TODAY of a hill of 400 -500 m. The Atlantic Rain Forest grows happily at +800 m

    Peter
    Yep. Eocene was warmer, as was the Cretaceous. However, it is very possible that this was due to increased ait density. See Journal of Experimental Biology 2018 Cannell Giant Dragonflies.
    In the Permian patm would have been about 1.6 bar for these bugs to function.

    Re Carbon budget
    This is difficult to follow – what is easier to check is the measurement of changes in carbon in forests. Burning thousands of ha of the Amazon, replanting tropical rainforest, etc. What seems to have been overlooked in the vast amount of carbon put into the atmosphere by the drowing (in just a few thousand years) of these forests. The ball park figures show that this was significant and lags sea-level rise. This offers an explanation for the “lag” in CO2 re T.

    • I found your article very informative for the simple reason that it gives me more areas to think about that I had never considered before. Thanks.

    • Alan Cannell,

      Thank you for your reply. Regarding the cause of the polar warmth during the Eocene Thermal Maximum (ETM), Wikipedia mentions several possible causes, and says that CO2 concentrations cannot explain it.
      Early Eocene and the equable climate problem https://en.wikipedia.org/wiki/Eocene

      The Early Triassic (250 Ma) was the hottest period. Most of the time from 542–365 Ma (Cambrian to Late Devonian) and 100–80 Ma (Mid Cretaceous) was hotter than the ETM. See Scotese (2018) chart on p3 here: https://www.researchgate.net/publication/324017003_Phanerozoic_Temperatures_Tropical_Mean_Annual_Temperature_TMAT_Polar_Mean_Annual_Temperature_PMAT_and_Global_Mean_Annual_Temperature_GMAT_for_the_last_540_million_years
      These charts are updated from Scotese 2016 which explains the methodology, but the update uses what is considered better data for the tropical temperatures.

      I’ll reply to your comment about the carbon budget later.

    • A check on the sea levels over the past several glacial cycles (500ka) given in the ref) shows that sea levels actually do stop at around 0 and 120m. The warming and cooling are processes that are based on the Milankovitch cycles, but with feedback mechanisms that stop the process at the stated levels.

      No sir, according to Spratt et al., 2016 the drop in sea levels:

      At 24 kyr BP stopped at –130
      At 135 kyr BP stopped at –124
      At 250 kyr BP stopped at –90
      At 340 kyr BP stopped at -100
      At 425 kyr BP stopped at –124
      At 540 kyr BP stopped at –67
      At 630 kyr BP stopped at –115
      At 720 kyr BP stopped at –90

      So only in two cases sea levels stopped at –120 m below current sea level. Four cases if –120 ± 10. Still another four cases between 20-50 m above that supposed target.

      It seems to me that the premise with which you start your article is not correct, regardless of what your reference says. There are no fixed levels. Melting and freezing proceed until they can’t for a variety of reasons, mainly due to Milankovitch orbital changes.

    • Allan Cannell

      Re Carbon budget
      This is difficult to follow – what is easier to check is the measurement of changes in carbon in forests. Burning thousands of ha of the Amazon, replanting tropical rainforest, etc. What seems to have been overlooked in the vast amount of carbon put into the atmosphere by the drowing (in just a few thousand years) of these forests. The ball park figures show that this was significant and lags sea-level rise. This offers an explanation for the “lag” in CO2 re T.

      By “difficult to follow” do you mean my comment is not clear, or that there is a lack of information on carbon content in the biosphere during earlier geologic periods?

      The burning of forests is mostly due to humans so is very recent – i.e. most has occurred during the last few centuries, and probably very little prior to the Holocene. The Pleistocene ice ages occurred before that, so the burning does not explain the lag in CO2 re T. The lag in CO2 re T occurred through all the Pleistocene glacial cycles. Further, plotting temperature from Scotese (2018) [1] against CO2 concentration from Foster et al (2017) [2] suggests the lags occurred throughout the Phanerozoic Eon, however, this might be due to the two studies using different dates.

      [1] Scotese (2018) https://www.researchgate.net/publication/324017003_Phanerozoic_Temperatures_Tropical_Mean_Annual_Temperature_TMAT_Polar_Mean_Annual_Temperature_PMAT_and_Global_Mean_Annual_Temperature_GMAT_for_the_last_540_million_years

      [2] Foster et al (2017) https://www.nature.com/articles/ncomms14845#f1

      I’ll add a separate, longer comment at the end of the current thread regarding my interests in the mass of carbon tied up in the biosphere and its implications. I’d welcome your thoughts on it.

    • Allan Cannell,

      Re: mass of carbon tied up in the biosphere:

      My interest in the mass of carbon tied up in the biosphere at different time in the geological past is what can be deduced about the impact of global warming on the biosphere. Several lines of evidence seem to suggest that global warming from the current icehouse conditions would be overall beneficial for the biosphere.

      First, IPCC AR4 WG1 Chapter 6 says:

      • 10% – 33% less terrestrial carbon storage at the LGM compared to today (300-1000 GtC less C in biosphere at GCM compared with preindustrial 3000 GtC) https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-4-1-4.html . That is, the mass of carbon in the biosphere has increased by a factor of 10% to 50% since the last glacial maximum.

      • “Lower continental aridity during the Mid-Pliocene” https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6s6-3-2.html

      Second, Gillman et al. (2015) Latitude, productivity and species richnesshttps://onlinelibrary.wiley.com/doi/pdf/10.1111/geb.12245found strong support for a negative relationship between latitude and annual [Net primary productivity] NPP of forests with all datasets, and NPP was significantly greater in tropical forests than in temperate forests. Vascular plant richness was positively correlated with NPP.” They find that “… annual NPP of forests with all datasets, and NPP was significantly greater in tropical forests than in temperate forests. Vascular plant richness was positively correlated with NPP.” They conclude “NPP of forests increases towards the equator. Given that species richness also increases towards the equator, and that vascular plant richness correlates with NPP, these results are consistent with recent meta-analyses showing that the relationships between productivity and species richness of both plants and animals in natural ecosystems are predominantly positive.

      Third, the benefits of a warmer planet for life are shown by the period from Eocene Thermal Maximum (50 Ma ago) to Present. Life thrived during warm and warming periods but struggled during cold and cooling periods. Mass extinctions were during cooling periods, not warming. Regarding the Eocene flora https://en.wikipedia.org/wiki/Eocene :

      At the beginning of the Eocene, the high temperatures (GMST 26.5 C, tropics 32 C) and warm oceans created a moist, balmy environment, with forests spreading throughout the Earth from pole to pole. Apart from the driest deserts, Earth must have been entirely covered in forests.

      Polar forests were quite extensive. Fossils and even preserved remains of trees such as swamp cypress and dawn redwood from the Eocene have been found on Ellesmere Island in the Arctic. Even at that time, Ellesmere Island was only a few degrees in latitude further south than it is today. Fossils of subtropical and even tropical trees and plants from the Eocene also have been found in Greenland and Alaska. Tropical rainforests grew as far north as northern North America and Europe.

      Palm trees were growing as far north as Alaska and northern Europe during the early Eocene, although they became less abundant as the climate cooled. Dawn redwoods were far more extensive as well.

      “The end of the Eocene was marked by the Eocene–Oligocene extinction event.” It was a cooling event.

      • @Peter Lang
        “The end of the Eocene was marked by the Eocene–Oligocene extinction event.” It was a cooling event.

        –which is common sense (uncommon in RL). Plants (& animals) grow better with warmth & lots of food (or CO2). Doh! For some reason, “Thermageddon” has taken hold of the Climate Alarmists. Weird.

      • The process of most relevance is net biome production – the difference between gross primary production and respiration. NBP is greatest at high altitude and high latitudes. Within reason. Biomass seems likely to be lost with warmer temps of a couple of degrees.

    • feedback mechanisms that stop the process at the stated levels. Topography is involved and this appears to relate to evaporation (water vapour) being a main driving force.

      When the oceans run out of enough thawed water to produce evaporation and snowfall, the process stops!

  6. This is an interesting post, but it boils down to yet another epicycle composed to justify CO2 as the thermostat. CO2 is a lousy thermostat. Taking the analogy of a room, if you set CO2 to warm your feet, it will also cool the air at the ceiling.

    • water freezes and thaws at the same temperature, CO2 does not change state in this temperature range. Water is abundant, CO2 is not.
      Water and ice and water vapor can be thermostats, CO2 cannot.

      • CO2 is well mixed. Water is not. According to MODTRAN CO2 concentration at the surface is the same as concentration at 70 Km.

        This permeation of the stratosphere allows CO2 to radiate upwards over 3 W/m2 at the tropical tropopause. All radiance above this point INCREASES in energy to the fourth power of the increasing temperature through the stratosphere. CO2 would be a better thermostat if it were less well mixed.

  7. I read the above and I exlained the above in much clearer terms and the one item you left out is RADIAT HEAT IS REFLECTED BY WATER.

  8. Nice post. Had not thought about the ‘limit set points’. Opens up some new lines for further self education. And, is also direct mechanism support for the dust/albedo theory for more rapid deglaciation than glaciation.

    • To the rapid deglaciation theory can also be added the bigger surface area of tropical waters. Tropical waters are the main absorbers of Sun energy.

      Besides, in circumstances of higher salinity of the sea surface some broad undeep waters could produce warm intermediate water – which will not be the case everywhere, due to lower densities because of higher rainfall and/or river runoff.

      Where warmer intermediate water wells up, the ‘surface start temperature’ will be raised.

  9. Hi Robert

    Sorry, I’m new to this, where did you explain the above?
    I avoided the radiated heat budget – far too complicated.

    Ceresco
    My job is to think about stuff that normally doesn’t get thought about, so thanks for the kind comment – it is what I aim at.

    Gymnosperm
    A very large input of CO2 and methane and – in particular – water vapour. All feedback to the orbital warming.

    BTW
    The ecology of the flooded areas in the Holocene looks like being a hot topic for the coming decades

  10. Alan wrote: “Water vapor is the most potent greenhouse gas and changes in sea level form a feedback process: when warming is taking place the ice caps melt and new areas of warm tropical seas are added that will increase water vapor in the air through evaporation …”

    I believe this part of your analysis is incorrect. What convection can only remove heat from the surface as fast as radiation transfers it to space from the upper troposphere! This is the rate-limited step in cooling the planet. You can’t have net evaporation if the upper atmosphere is too warm for an unstable lapse rate to develop somewhere.

    The rate of evaporation is determined by two factors: wind speed and undersaturation ((1-RH)*saturation vapor pressure). If the upper troposphere is too hot to permit convection, relative humidity rises or wind speed falls. This is how climate models reduce the rate of increase in precipitation from the expected 7%/K to around 2%/K.

    The situation is somewhat different over land (and you are discussing more land). But the principle is the same: heat must leave the upper troposphere before convection can develop.

  11. Alan wrote: “During the stable glacial maximums, the present day coastlines were 120 m above sea level. Thus the drop in air pressure over present land expressed in equivalent present day height above sea level would be.”

    This may be incorrect. Surface air pressure is due to the weight of the atmosphere above the surface. With the exception of a slightly stronger pull of gravity from being 120 m closer to the center of the Earth, the weight of the atmosphere is proportional to its mass. Unless you add mass to the atmosphere, surface air pressure can’t rise.

  12. I’m a bit skeptical about all global warming and cooling being related to changes in CO2 uptake and outgassing on the vast periphery the continents as sea level rises and falls on millennial timescales. Where does changes in solar activity enter the equation?

  13. Javier
    The point made is that sea levels drop to around -120 m – but not further – and rise to 0 – but not higher. The data set from the Red Sea gives more consistent values. These constraints fit the current topography and follow the simple equation. If cooling stops the cut-off is not reached. Evaporation over tropical and sub tropical seas (where evaporation is highest) seems to be the main factor. Like most engineers, I like something simple that works and fits the data.

    Peter
    “Hard to follow” means hard to figure out where all the C is stacked. I go no further than to estimate the mass of CO2 from ppm data and then add the new carbon stock from drowned forests. My interest in this started (as a plaeoanthropologist) in relation to human migration in the Holocene. Newly exposed beaches would be natural pathways, drowned tangled forests a nasty trek. Carbon from drowned forests has been overlooked and/or downplayed and may be a hot topic for the coming decades. To give an idea: at low sea-levels the western Malvinas cold current (from the Antartica) would be greatly reduced (by about 80%), so the exposed Atlantic Argentine Continental Shelf would have been warmer and less steppe like & MAY have been wooded (those giant sloths browsed on a lot of greens). This area is huge at about 500k km^2 and did not enter into the drowned forest carbon estimate – nor did other temperate forests..

    The Early Triassic was cold for about 500 ka, my own take on this being a loss in patm at the end of the Kiaman superchron. For those interested may I suggest the Overview: Giant Bugs, Martian Air Ice Ages etc. Version 7 on my Researchgate page.
    The JEB paper on the Engineering of Giant Dragonflies (also on the RG page) is an attempt to quantify patm in the Permian from fossil biology – I get about 1.6 bar.

    • The point made is that sea levels drop to around -120 m – but not further

      Alan, the point has not been made. How do you know that the stopping of the cooling is not responsible for the stopping of the sea-level drop? We know that the cooling causes the sea-level drop, as it starts earlier. To make your point you would need a period of significant cooling after reaching -120 m when there is no further sea-level drop, showing that there is a temperature-independent limit. Good luck finding it.

      • Alan Cannell

        For the present topography such a deep freeze as this has never existed.
        And we don’t know what would happen in an extra-long GM. The Red Sea data quoted (which does not have currents, tides, geoids and winds) however, does show remarkably consistent max & min. (over the Hanish sill) with near present levels (within 10 m) at today, 120 ka 200 ka 235 ka 335 ka & 410 ka, and low stands at 20 ka, 140 ka and 440 ka.
        This does relate to topography and tropical sea surface area and may be of interest.

      • There are no extra long GM because they are constrained to a bottom in the obliquity cycle (with adequate climatic lag of ~ 6 kyr), so their length is limited to a slightly over a quarter of 41 kyr or about 10-15 kyr.

        I see you have decided that your local Red Sea data can be trusted better than more global reconstructions and δ¹⁸O stacks that are a proxy for global ice. There is a lesson to be learned from the 1470-yr periodicity found in GISP2 during the last glacial and trusted despite not showing in other cores because GISP2 was supposedly a superior core. That avenue leads to the wrong conclusions and publishing articles like Rahmstorf et al. 2003 that looks ridiculous a few years later.

        When only one proxy shows what you want, the prudent position is to be cautious.

      • Alan Cannell

        The Red Sea data first caught my eye (Eelco Rohling et al) as the upper and lower msl limits are so clearly marked. As this area is free from tides, currents, monsoons and geoids it serves as a good reference. Other and more recent extrapolations are not much different, hence the interest in finding out if any link exists (not to the levels between the limits but to the limits themselves). There is a topographical link which suggests that evaporation between 30S&N (where most evaporation takes place – considered common knowledge & ref not given) and water vapour thus seems to be the driving force on both cooling and warming during the last 700 ka or so and therefore CO2 plays a lesser role.

    • Alan Cannel,

      Thank you for your reply. Our reasons for our interest in paleo climate and biosphere productivity versus temperature over geological time are clearly quite different. You appear to be mostly interested in the last glaciation and Holocene. My interest in this discussion is about the period since complex life began, biosphere productivity versus GMST, and the causes of the mass extinction events.

      Yes, there is recent evidence that the Permian-Triassic Boundary was a short ice age and a mass extinction event. Baresel et al (2017) https://www.nature.com/articles/srep43630 , give the timing as ~89 ka in the Permian and ~14 ka in the Triassic.

      I can’t comment on the impact of drowned forests on atmospheric CO2 and GMST. However, my suspicion is that it is trivial. We’d need to see the estimated quantities and compare these with the masses of C in the biosphere, oceans and calcareous sediments – e.g. as given by Mike Jonas in this comment above https://judithcurry.com/2019/01/04/sea-levels-atmospheric-pressure-and-land-temperature-during-glacial-maxima/#comment-887416 . We’d also need to understand the emissions rates and sequestration rates (oceans, vegetation and weathering) and compare these with the rates from all other sources.

    • 1.6 bar surface pressure would in itself explain the escape from the Carbo early Permian glaciation and the extremely high temperatures (accompanied by sea level low stand) at the P/T extinction.

      By most accounts high temperatures continued through the early Triassic and the whipsaw biological recovery.

  14. stevefitzpatrick

    A lot of what is in this post is simply wrong, and most of the rest irrelevant. Atmospheric pressure does NOT fall significantly when land supported ice accumulates; land supported ice mostly displaces the atmosphere (very little air is sequestered in the ice), and atmospheric pressure at the ocean surface rises by approximately the equivalent of ~120 meters of altitude if sea level is 120 meters lower. If we use the ‘standard atmosphere’ lapse rate of ~6.5C per KM, that is equivalent to a 0.78 C increase in ocean surface air temperature (all else equal). All that low altitude exposed land will also have more atmosphere above it for the same reason… and be a little warmer than it would otherwise be.

  15. Hi Steve
    Yep, patm at sea level is pretty much the same; a bit less for the air lost in ice, a bit less from the lower water vapour.
    The point being made is that for PRESENT land, the equivalent loss in patm is all the above PLUS the new height. So in Curitiba (where I live at 940 m above sea-level, during the LGM the house would be 1060 m plus the effect of the lesser patm.

    • stevefitzpatrick

      Meu amigo, você está totalmente enganado sobre isso.

      The density of glacial ice is lower than water (~0.917 g/ml at depths >200 meters) so the loss of volume of “sequestered air” is almost perfectly compensated for by the greater volume of ice versus the same mass of water. As the ice sheet builds, the loss of ocean volume is almost identical to the increase in volume of ice… which displaces the atmosphere where ice sheets form….. meaning that at a fixed altitude (relative to the Earth’s center, not relative to sea level), there would be no significant change in atmospheric pressure. So unless Curitiba changed altitude significantly due to isostatic adjustment (I doubt this… glaciers were pretty far away: https://en.wikipedia.org/wiki/Last_Glacial_Maximum#/media/File:CLIMAP.jpg), the atmospheric pressure at ground level would be virtually unchanged during the last ice age versus today. Note in the map linked above that the ocean surface temperature in much of the Pacific was *WARMER* than today (temperature estimate based on analysis of ocean sediment). This is consistent with HIGHER atmospheric pressure over the Pacific, not lower.

    • stevefitzpatrick

      Alan,
      “Yep, patm at sea level is pretty much the same;”

      Nope, and this is the biggest reason your analysis is just wrong. patm rises a bit at sea level when Ice sheets form, and stays almost the same at a fixed altitude (distance from Earth’s center) on land.

  16. I assume that the direct effect on air pressure on land of a 120 m lower sea level is small.
    Transforming 120 m water to ice increases volume by SE * 0.7 * 120 * (1/0.917 – 1)= SE * 7.6 m, so air pressure increases by ~8 m (SE= surface of the Earth).
    However, the density of the air displaced by the ice is lower than that of the air above the lower sea level. Assuming an increase in height of 1 km for an average water/ice particle, this effect results in an 11 m lower air pressure.
    The net result would be a 3 m lower air pressure on land and a 117 m higher air pressure at sea level, from which the other effects of 20 m (air sequestration) + 10 m (glacial deformation) + 45 m (loss of gaseous water) have to be subtracted.

  17. The relative lowering of sea level would have had the effect of adiabatic warming of SST which would go a long way to describing the CLIMAP observations.

    This would also have had an impact on the dynamics.

    In addition to the orographic obstruction of the ice sheets, relative to sea level, the mountainous terrain would have had a greater impact and the potential energy of air masses at sea level would have been lower. It’s speculative, but one can imagine more sunny subtropical ocean days because even with the greater overall kinetic energy, subtropical air masses would have been less easily displaced.

  18. “The covariation of carbon dioxide (CO2) concentration and temperature in Antarctic ice-core records suggests a close link between CO2 and climate during the Pleistocene ice ages. 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 during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing CO2 concentrations is an explanation for much of the temperature change at the end of the most recent ice age.”

    http://www.atm.damtp.cam.ac.uk/mcintyre/shakun-co2-temp-lag-nat12.pdf

    Both biokinetics and geophysics suggest that substantial lag between CO2 and temperature is improbable. It seems rather to be more an artifact of antiphase polar warming.

    e.g. – https://s3.amazonaws.com/academia.edu.documents/33489657/QSR-Ohetal.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1546808572&Signature=eYDVex8KSabW5suta6cFLAPODgU%3D&response-content-disposition=inline%3B%20filename%3DPolar_synchronization_and_the_synchroniz.pdfhttp://www.ajsonline.org/content/312/4/417.abstract

    More generally I find the geophysics of this post problematic, the assumptions and calculations simplistic and the presentation crude.

  19. Robert
    There is a saying in Brazil: why simplify things if we can make them more complicated (and earn a living from it)? I’ve seen this temperature and CO2 graph before and I think the question of why the scales are set this way (comparing apples and pears?) has been raised.
    The chicken and egg question of lag has followers in both camps, however, that there is a feedback between T and CO2 is not in any doubt. How much is from drowned forests (and savannahs etc.) seems to have been overlooked, hence the crude (yep) engineer’s, back-of-an-envelope calculation to check on the magnitude. One comment says that “this would be insignificant”, the numbers I get shows that this could be a significant part of the feedback. I look forward to seeing this topic being taken up by the professionals and the data refined.

    • “Everything should be made as simple as possible, but no simpler.” Albert Einstein

      Biokinetics imply balance between respiration and photosynthesis that results in increases or decreases in net biome production. Both on land and in oceans. A global process of course as much in high latitudes – especially in oceans – than in tropics.

      Carbon dioxide solubility with temperature is a relevant feedback.

      These are fast processes and the parsimonious explanation is that the 800 year lag is an artifact of paleoclimatic data sources. Resorting to quibbling about data – and ignoring antiphase polar temperature changes that were at the core of my comment – is disingenuous.

  20. Unfortunately I am not too familiar with antiphase polar T changes & the link gave a 404, so I am not able to add anything on how this relates to the points raised in my post. In a nutshell: max and min sea levels are largely determined by the topography of the continental shelves; cooler T over PRESENT lands is affected by altitude (patm) – hence the exposed shelves at -100 to -120 m were slightly warmer & this allowed more tropical and sub tropical forest growth – such as the Atlantic Rain Forest – and these forests (covering an area about the size of Brazil) were drowned and the corbon stored presumably lost into the atmosphere in a very short period.
    If I may, I’ll restrict future replies to these questions.

    Steve
    I have done a new data search and will post a reply tomorrow.
    Eh uma bagunça!

    Best

    Alan

    • Alan Cannell,

      … these forests (covering an area about the size of Brazil) were drowned and the carbon stored presumably lost into the atmosphere in a very short period.

      What mass of carbon do you estimate was released from submergence of these forests, what proportion went to the atmosphere and what went into the oceans, and over what time period? I Understand it took around 10,000 years for sea level to rise from LGM.

      • Peter
        From the literature the mechanism seems to be that the trees die from salt water in the roots and rot aerobically (bacteria) into methane and CO2 (initially air). The remains are broken down by wave action and consumed by worms etc. The organic parts of the soils as well.
        As nothing is left, these huge forests appear to have gone into thin air – the Drowned Forest Effect seems to have been overlooked, so nobody really has any idea on what went into air, the sea or new forests as the ice retreated and present land warmed. I have seen estimates of carbon in new forest growth. In time, either the Drowned Forest Effect will be of interest to the community or it will be dismissed as rubbish. The numbers point to a real effect, as does the higher patm (T) on the exposed lands (pls see the reply to Steve).

    • From the link under the graph – that you said you had seen.

      “The covariation of carbon dioxide (CO2) concentration and temperature in Antarctic ice-core records suggests a close link between CO2 and climate during the Pleistocene ice ages. 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 during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations
      in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing CO2 concentrations is an explanation for much of the temperature change at the end of the most recent ice age.”

      Or this?

      http://www.ajsonline.org/content/312/4/417.abstract

      So two out of three. Here’s the other.

      https://www.sciencedirect.com/science/article/abs/pii/S0277379113004198

      Yes – I’d suggest you focus on the emerging land – everything else seems irrelevant. But there your carbon cycle misses far too much to be interesting.

      • It looks like the Drowned Forest Effect has been overlooked and may be worth raising. As replied to Peter, I have no idea where this carbon went (nobody has) and how it would fit into the very short-term carbon cycle. A hunch would be that there is a lag between the drowned carbon and the full grown new forest carbon, thus a climate optimum at the end of the sea-level rise – which seems to fit the data.
        Nice MSc thesis for someone!

    • stevefitzpatrick

      Bargucada na mesa e uma coisa….. bargucada em pensamentos e outra.

  21. .
    ❶①❶①❶①❶①❶①❶①❶①❶①❶①❶①❶
    ❶①❶①
    ❶①❶① . . . A global warming paradox . . .
    ❶①❶①
    ❶①❶①❶①❶①❶①❶①❶①❶①❶①❶①❶
    .

    Imagine that you have a “big” date range, which has a warming rate of “B” degrees Celsius per century.

    You decide to split the big date range at a year somewhere near the middle of the big date range, to give 2 smaller date ranges.

    It important to realise, that joining the 2 smaller date ranges together, produces the original big date range.

    There is no overlap between the 2 smaller date ranges, and there is no gap between the 2 smaller date ranges. One smaller date range stops, where the other smaller date range starts.

    The 2 smaller date ranges have warming rates of “S1” and “S2”.

    What is the relationship between “B” (the warming rate of the big date range), and “S1” and “S2” (the warming rates of the 2 smaller date ranges).

    Do “S1” and “S2” have to be near “B”?

    Does “B” have to be near to the average of “S1” and “S2”?

    ====================

    Have a look at these 2 graphs:

    http://woodfortrees.org/plot/uah6/trend/plot/uah6/from:1978/to:1998/trend/plot/uah6/from:1998/to:2019/trend/plot/uah6/mean:12

    http://woodfortrees.org/plot/uah6/trend/plot/uah6/from:1978/to:1999/trend/plot/uah6/from:1999/to:2019/trend/plot/uah6/mean:12

    Can you explain what is happening in these 2 graphs?

    This example uses UAH global lower troposphere temperature anomalies.

    The big date range is 1980 to 2018.

    In the first graph, the 2 smaller date ranges are 1980 to 1998, and 1998 to 2018. Both of the smaller date ranges, have warming rates which are considerably lower than the warming rate of the big date range.

    In the second graph, the 2 smaller date ranges are 1980 to 1999, and 1999 to 2018. Both of the smaller date ranges, have warming rates which are higher than the warming rate of the big date range.

    How can this be? There is only 1 year difference, in where the big date range was split. But the warming rates of the 2 smaller date ranges, do opposite things in the 2 graphs.

    ====================

    Try to work out the reason, for these apparently contradictory results.

    If you want some help, or you want to check your answer, then read this article:
    https://agree-to-disagree.com/split-date-ranges

  22. Steve and Franktoo [IN FACT ALL READERS AS THIS IS AN IMPORTANT POINT THAT THE GUYS HAVE RAISED}

    The question of patm at new sea levels is one which has been a bit confused since the original work by Mélières et al 1991, in which she shows (by using overal air mass) that sea-level pressure was pretty much the same in the LGM – without making it clear which sea level was being mentioned (mslP) present or msl LGM.

    Using the fluid analogy you get that patm at mslP does not change – I got stuck on this as well. Thinking in terms of gas, in which the large volume of ice is very small in relation to the overall volume, you get that patmLGM (the bottom of the air ‘column’ is pretty much the same as patm mslP.

    So before reaching for the digital ink, let’s see what the pros do. A quick check showed that climate models of the LGM that take into account exposed lands and ice use patm at mslLGM as the same as present values:
    S.-J. Kim G.M. Flato G.J. Boer
    A coupled climate model simulation of the Last Glacial Maximum,
    Part 2: approach to equilibrium Climate Dynamics (2003) 20: 635–661
    DOI 10.1007/s00382-002-0292-2

    The LGM surface climate and atmospheric circulation over East
    Asia and the North Pacific in the PMIP2 coupled model simulations
    W. Yanase and A. Abe-Ouchi1,
    Clim. Past, 3, 439–451, 2007

    Now we can thump the table with a “Fools, they’re all wrong”, but, fortunately I also found new empirical data from the tropics (thanks Google) from last year. All engineers love empirical data (it works and is normally easy to understand) and this shows that during the LGM the T gradient was higher (possibly because it was drier) at 6.7 C/1000m (up to 3000 m), they also show/model that the tropical SST was only 1- 2C cooler than present and that their modeling (using -135 m as msl LGM) thus gives the recorded T by adding in the lower T due to the higher altitude as patm at their mslLGM is pretty much the same as the present:

    SCIENCE ADVANCES tropical lapse rate steepened during the Last
    Glacial Maximum
    Shannon E. Loomis,1 James M. Russell,1,2* Dirk Verschuren,3 Carrie Morrill,4,5 Gijs De Cort,3,6
    Jaap S. Sinninghe Damsté,7,8 Daniel Olago,9,10 Hilde Eggermont,3,11
    F. Alayne Street-Perrott,12 Meredith A. Kelly13

    I have been in contact with Dr Loomis to check on o few points (their graph actually shows a T drop of about 1.4 C between msl LGM and mslP).and how they chose patm at mslLGM.

    And now we get to the part that is of real interest. The fuzzy thinking (a bagunça) concerns most comments on cooling during the LGM. Normally this is termed as “over patagonia T were some 5-7 C cooler” or “in Southern Brazil T were 5-7 C cooler”… These should have the caveat: OVER PRESENT LAND.

    Down on the new coast (msl LGM) it was a bit warmer – between 1 to 2 C at -120 m – say 5- 3 C cooler in S Brazil (I think we can all agree on this?) and thus closer to the tropical SST. This has a huge impact on the forests that grew on exposed lands (pls check the late ref on the Atlantic Rain Forest which gives an idea of this part of the world) and would thus allow forests to develop further to the S & N.

    An estimate of the Carbon in these forests (crude & simple) is given in the post. It seems to be significant and this Drowned Forest Effect seems to have been overlooked. Possibly because it really did dissapear in a geological blink into thin air leaving little hard evidence behind (except perhaps a warming pulse from CO2 & a lot more water vapour and thus more clouds/wracks) .

    Looking at these issues and comments I found that the paper on the Atlantic Rain Forest may even be conservative in the S range of this biome. The W part of the Malvinas Current would have been a lot weaker (due to the exposed lands) and thus the exposed Argentine shelf may have been warmer and wetter, allowing for the spread of the ARF to the Plate. Big area and more Carbon.

    I’ll take this up with the guys working on this and we shall see if this leads to anything of use. So thanks to all for the feedback and interest!

    Alan

  23. Alan Cannell: The question is not so much why these cycles occur, but why do they stop at these depths?

    Good question!

    Thank you for your essay.

    • Thanks Mat

    • The deoth if the ocean at the beginning of the Ice Age and at the height of the ice ice build up is relatively the same for each ice age is because the bottom of the ocean is relaatively constant over the mellenia. The surface area of the earth covered by water and land is therefore the same. The radiant heat reflectred by the ocean is relatively the same.

  24. off topic for today, but of interest at other times:

    Mobbing in Academe

    https://mail.google.com/mail/u/0/#inbox/FMfcgxwBVDCvpJlJqWcTSfPSMslQRpld

  25. Geoff Sherrington

    Alan Cannell,
    To the generalist, this topic seems amenable to modelling of position shifts of masses of air, water, solids according to observational amounts and directions.
    But when I try to imagine a scheme of analysis, some variables seem to be causes of problems. The one that presently worries me most is the viscosity of sub-ocean lithologies and then the geometries of their movements under applied forces.
    One can imagine a situation whereby more water put into an ocean does not change the ocean level relative to say an ancient craton shore line, because the ocean floor simply lowers itself in compensation for the added mass above it. Next thought is that to lower the ocean floor might require sideways rock movement and that implies causing an elevation change elsewhere. Such an elevation has one consequence if it happens under land, another if under the oceans. The problem becomes quite complex and its solution needs observational data not yet acquired AFAIK. That is my mind’s main problem here.
    Alan, what limiting process seems to you to dominate the analysis?
    Where should researchers be measuring to get the data to allow a model to work well?

    Please excuse me if my words do not meld with your important points in the header, which I found rather thought-provoking. In my student days we simply regarded ocean floors as fixed in place for all intended purposes so it is likely that I have missed some of your important conclusions. Geoff.

    • Like you, this is very complex. For the past 500 ka we may assume that both continents and ocean floors have changed very little so these effects do not affect the points I raised. This is probably true as far back as the Miocene, but not for the K where the Atlantic was being formed, the Pacific was being enormously expanded and the Thetys was presumably a large body of shallower water. K se-levels can thus be taken with a very large pinch of salt – what is of interest though is their relative shift – which can be identified and hints at ice formation or other factors. All very much out of my area I’m afraid. For the time being I hope to focus on getting data on the Drowned Forest Effect.
      Alan

  26. .
    ❶①❶①❶①❶①❶①❶①❶①❶①❶①❶①❶
    ❶①❶①
    ❶①❶① . . . The Comb of Death . . .
    ❶①❶①
    ❶①❶①❶①❶①❶①❶①❶①❶①❶①❶①❶
    .

    What, you may be wondering, is the “Comb of Death”?

    In simple terms, it is a graph that looks like a comb.

    But, what has it got to do with Death?

    Well, “The Comb of Life” didn’t sound very exciting. But “Death” is a certain winner.

    And it is showing “global warming”. That causes a lot of deaths.

    Or it will in the future, if the “Comb of Death” is correct.

    The “Comb of Death” displays temperature ranges, for more than 24,000 locations on the Earth.

    And I am talking about REAL, ACTUAL, ABSOLUTE temperatures. Not those weak, pale, temperature anomaly things. But real, actual, absolute temperatures. The sort that REAL men use (and REAL women too).

    ====================

    The Oil companies offered me a lot of money to “forget” about the “Comb of Death” with +3.0 degrees Celsius of global warming. But I am an artist, and they didn’t offer me enough money.

    Because people are not making enough effort to reduce their carbon footprints, the IPCC has asked me to show you a “Comb of Death” based on +3.0 degrees Celsius of global warming.

    They expect that this “Comb of Death” will make Alarmists scream in fear, and will make Skeptics repent their evil ways. A word of warning, this last “Comb of Death” is not for the faint-hearted.

    https://agree-to-disagree.com/the-comb-of-death

  27. There is a misunderstanding of the ideal gas equation that appears to be unquestioned here – emerging as it does from the Venus meme.

    T = pV/nR

    see – https://www.chemguide.co.uk/physical/kt/idealgases.html

    As an instantaneous response or in an isolated system – putting a gas under pressure will result in a temperature rise as a result of confining kinetic energy to a smaller space. A system that is not thermodynamically isolated will return to a local thermodynamic equilibrium.

    • Robert
      This is a different point that I have seen raised before in relation the ideas of Ned Nikolov and Karl Zeller. They claim that surface temperature is basically a function of pressure. Given the physical characteristics of an atmosphere: composition, water vapour, CO2, methane, etc. and the energy applied (from the sun), surface temperature is a function of pressure: heat being an expression of the extra energy released through constraining the gas.
      When you go down the mountain it gets warmer by about 6 C per 1000 m.
      If patm on Earth were increased so that we lived (on the beach) at -1000 m, the surface temp would be about 6 C warmer. Nothing else has changed. The snow line, of course would be 1000m higher and a lot of ice would melt. There is very little change in the thermodynamics.
      Alan

      • Heat is transfered three ways, Conduction, Convection, and radiant. Radient is the only one that goes thru a vacuum. The earth gains radient heat from the sun, and looses radient heat to outer space, black sky, 24 hours a day. The reflected radient heat also goes to the black Sky.

      • Heat is a measure of the kinetic energy of molecules. The zeroth law of thermodynamics applies.

  28. It appears mean sea level pressure has been going down in the modern era.

    https://climatedataguide.ucar.edu/climate-data/cera-20c-ecmwfs-coupled-ocean-atmosphere-reanalysis-20th-century

    Is there a standard explanation for this?

    I also notice that many climate models predict lower air pressures with warming.

    https://www.researchgate.net/figure/Thirty-year-running-annual-means-for-a-2-m-air-temperature-b-total-precipitation_fig7_262098371

    Do these climate models have it wrong? Yet the instrumental record appears to agree with them to some extent.

  29. This paper indicates that the atmospheric pressure decreases during deglaciation, therefore it increases during glaciation.

    https://www.sciencedirect.com/science/article/pii/003101829190170V

    Here is the abstract:

    “The change in the global mean atmospheric pressure between glacial and interglacial periods is evaluated at sea level. This change originates in a modification of topography and in a possible variation in the atmospheric mass. In this calculation the atmosphere is at hydrostatic equilibrium, and the parameters describing the glacial period are varied in a plausible range. The result, with constant atmospheric mass, is a mean sea level pressure decrease of 9–15 hPa linked with the deglaciation. The corresponding pressure change at the reference level corresponding to the present day sea level does not exceed one hPa. When considering only the change in the atmospheric mass, an increase which does not exceed 2 hPa is found, linked with the deglaciation.“

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