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Do high levels of CO2 in the past contradict the warming effect of CO2?

What the science says...

Select a level... Basic Intermediate

Climate and CO2 levels have always varied together. During past ice ages CO2 levels were low, and during warm periods CO2 was higher.

Climate Myth...

CO2 was higher in the past

"The killer proof that CO2 does not drive climate is to be found during the Ordovician- Silurian and the Jurassic-Cretaceous periods when CO2 levels were greater than 4000 ppmv (parts per million by volume) and about 2000 ppmv respectively. If the IPCC theory is correct there should have been runaway greenhouse induced global warming during these periods but instead there was glaciation."
(The Lavoisier Group)

At a glance

Before diving headlong into this myth, one key thing needs to be pointed out. The confidence expressed in the above statement. Phrases like 'killer proof' should be enough to ring alarm bells warning the statement is not the work of any credible scientist. Scientific writing is a relatively sober business.

That aside, this myth is about the nature of Earth's atmosphere and climate through deep time. We know quite a bit about that atmosphere now - but far from everything. Through geological studies, we know a lot more about how the planetary climate evolved over time. But far from everything. It's work in progress.

Evolution of climate over deep time was governed by several factors. Fluctuations in the carbon cycle were driven by changes in the balance between CO2 sources and sinks. In those pre-human times, the key CO2 source was volcanic and the key sink was, as now, weathering. Volcanism is still a significant CO2 source - but about a hundredfold less than human emissions.

Weathering is a chemical reaction that involves the breakdown of the minerals making up the rocks of Earth's surface. Its key agent is carbon dioxide dissolved in rainwater, this being a weak acid. Since rainwater delivers the CO2, the intensity of weathering will partly depend upon rainfall. In turn, that depends on how wet - or dry - the climate happens to be in any given place at any given time.

That leads us into palaeogeography - the science of how the layout of the globe has changed through time. Slow changes in layout are driven by plate tectonics and continental drift. Geological evidence tells us that most of the continents on Earth were sometimes gathered together, to form 'supercontinents'. At other times, they were widely dispersed. Such changes in layout through deep time had implications for both the climate and intensity of weathering.

In general terms, the dry interior of a supercontinent reduces weathering, allowing CO2 levels to rise because the sink cannot keep up with the source. A dispersed pattern is a lot better for weathering and the sink can outpace the source, allowing CO2 levels to fall.

Over geological timescales, changes in Solar brightness matter, too. Solar brightness is considered to have increased steadily by about 10% per billion years of Earth's history. In the late Ordovician, 445 million years ago, there would therefore have been 4-5% less sunshine reaching the Earth. That's a big difference and enough to change what is known as the 'ice-threshold' - the point beyond which perennial ice-sheets can exist on Earth's surface.

There was certainly an ice-age in the late Ordovician. There are multiple lines of evidence that lend support to that statement. Dispersed continents favoured weathering and CO2 drawdown. Because of the dimmer Sun, the ice-threshold was set at a much higher CO2 level than in more recent times. Something else happened too. The late Ordovician ice-age was accompanied by the second-greatest mass-extinction in the fossil record. Neither the quote nor its parent document mention that. One wonders why.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


Further details

Although our understanding of atmospheric composition through deep time is still a work in progress, we now know enough to state that climate and CO2 levels have always varied together. During ice ages CO2 levels were low, and during warm periods CO2 was higher.

In the Eocene (56-34 million years ago) there were no polar ice caps, temperatures were about 10ºC hotter than the 20th Century, and CO2 was about 1,500ppm (Westerhold et al. 2020, Rae et al. 2021). During the last Ice Age, CO2 varied between about 180 and 300 ppm as ice sheets waxed and waned with orbital wobbles (Rae et al. op.cit.). CO2 was also about that level during the late Paleozoic Ice Age, 340-290 million years ago (Foster et al. 2017).

Early attempts to estimate CO2 for that long ago in Earth’s past were broad-brush and very uncertain (e.g., Royer 2006), leading to the high CO2 estimates referred to in the myth. New data and refined techniques have since clarified the picture considerably. The 2006 estimates, for example, averaged data across 10-million-year timesteps, the 2017 data in the figure below used 0.5-million-year timesteps, and newer compilations don’t average across timesteps. At the same time, CO2 and temperature uncertainties have reduced considerably so that climates from the geological past (e.g., Fig. 1) are now a useful reality check for climate models (Tierney et al. 2020, IPCC 2021, see the intermediate version for more detail).

Data for the Ordovician are less certain, but they suggest that CO2 was about 2,400ppm and falling before the end-Ordovician glaciation (Pancost et al. 2013). Glaciation at higher CO2 levels than today was possible at that time for a variety of reasons including a less-bright Sun back then (see the intermediate version). The Jurassic and Cretaceous span 134 million years with several hothouse episodes and several cooler episodes, with CO2 varying from about 600 ppm to about 1500 ppm accordingly (Witkowski et al. 2018), but there was no glaciation in that time. Earth’s long-term climate (over millions of years) is governed by the balance between CO2 emitted into the atmosphere by volcanoes and CO2 removed from the atmosphere by weathering of rocks. This has prevented runaway climates and kept Earth’s climate generally habitable for about 4 billion years, but it can be outpaced by abrupt greenhouse gas releases (e.g. at the end-Permian mass extinction), or removals (e.g. “Snowball Earth” periods).

CO2 for the last 420 Million Years

Figure 1. CO2 levels for the last 420 million years, showing periods with ice ages. Note this curve is smoothed and too low resolution to show spikes in CO2, eg at the end-Permian, end-Cretaceous, PETM, etc. Data from Foster et al. (2017). Late Paleozoic Ice Age per Rolland et al. (2019). Preindustrial CO2 278 ppm, 2021 CO2 420ppm (CO2.Earth). Newer data zooming in on the last 66 million years can be found on the intermediate tab.

Nevertheless, Earth's climate system has, for the most part, maintained a near-balance in terms of the overall habitability of the planet. This is despite periodic shocks of an internal (e.g. supervolcanic eruptions) or external (e.g. giant impacts) nature. That the key pre-human source of CO2 was volcanic activity and that volcanic activity is largely driven by plate tectonics is likely to be the key to this stability. Plate tectonics is a constant, ongoing process and probably has been for much of Earth history. That CO2 sources and sinks mostly do not stray too far apart - with the unique exception of human emissions - is very likely to be down to plate tectonics and its vital role in the Slow Carbon Cycle through geological time.

Last updated on 7 October 2023 by John Mason. View Archives

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Comments 76 to 100 out of 105:

  1. Norm. First off, no scientist that I am aware of is claiming the putting CO2 into atmosphere could cause a runaway greenhouse. Certainly the consensus opinion is that there is no possibility of a runaway greenhouse. This is a strawman argument. It is best when making a claim that "science is wrong" that you cite science claim that you are disputing. This avoids timewasting with strawman arguments.

    Will adding more CO2 increase temperature? Yes, just a plainly as increasing output from the sun would increase temperature. You can measure it directly. However, figuring out how much it will rise depends on feedbacks which are much harder to determine hence the wide error bars on constraining climate sensitivity. See here for more on runaway feedback

    Reading the IPCC WG1 report or at least the summary for policy makers would help you in understanding what claims the science is actually making.

  2. It would be good to see an explanation of something other than the Ordovician here... the Earth then was so different in a lot of important ways it's difficult to trust any conclusions. What about Cretaceous or Paleogenic Earth? The CO2 levels then are more comparable to where we are headed, and geological and biological factors are likely more similar. 

  3. I am skeptical of the authors conclusions: the argument is that "coincidence of conditions" counteracted the CO2's warning effect at such high levels, at the period in question. But the levels of CO2 are being doubted due to large uncertainties in the extremely ancient evidence, yet the same, if not more, uncertainties exist for the "coincidence of conditions" due to the extremely old evidence. There's lots of evidence to make one skeptical about climate science assertions, not the least of which is all the hysteria around the subject.

  4. Warend @78,

    Ancient evidence can obviously come with uncertainties that can be very large. However you are wrong to suggest that the argument that CO2 levels dipped in the Late Ordovician rests solely on "large uncertainties" or in other words "we don't know that it didn't dip."

    There is evidence cited (Young et al 2008) in the Intermediate version of the OP above showing that, prior to the Late Ordovician, CO2 was high due to high levels of volcanism but not very high due to high levels of rock weathering. And the evidence shows the high levels of volcanism stopped before the rock weathering ended causing CO2 levels to drop to below 3000ppm, a level which would allow glaciation with the weaker sun. This is the "coincidence of conditions" mentioned in the OP summary.

    And the scientific work has continued through the years allowing a more detailed understanding of the events that created the Late Ordovician glaciation. See for instance Ghienne et al (2014) or Pohl et al (2016). Past uncertainty is today reduced to the point of no-longer being uncertainty.

  5. How do you know for certain the sun was "weak" at this period of time? What level of uncertainty has been determined for these studies conclusions. I can assert that - we do not know for certain what happened so long ago, and we do not know what level of uncertainty we are working with. How do you suggest calculating the mathematical level of uncertainty for occurances so far in the past?

    Response:

    [PS] bombing multiple comment threads with weak comments is verging on sloganeering. Stick to where you have the problem, engage with other commentators and move on when resolved please.

    The sun early output is from basic physics of its state as a main-line star. I am unaware of any serious doubt on the physics of stellar evolution that would challenge that conclusion.

  6. I am not challanging the theory or formulations that compose stellar evolution models. But what are the degrees of uncertainty or variance between calculated model results and actual stellar luminosities over time. Because of the time scales this cannot be done directly with observations over time. Looking at published solar luminosities the solar intensity was 11% less during the start of the glaciation event...assuming a 25% forcing contribution due to solar radiation this yields a nominal forcing effect of ~3%. But again what's the uncertainty...I so far have not found a published value. This is understandable given the time frames and the current impossibility to conduct validating experiments. There was some mention of errors in the range of 10 to 15%. If that is the degree of uncertainty in the stellar model results, that would say that there is too much uncertainty relative to the nominal effect. Perhaps there are similar uncertainties, and effect level magnitudes, with the other coincidental conditions/effects?

  7. Warend @81,

    You state that published solar luminosities show "the solar intensity was 11% less during the start of the glaciation event." That seems very high. Are we talking about the same "glaciation event"? Perhaps you could point to the publications you cite. A simple Wikithing reference gives Fig 1 from Ribas (2009) below which suggests a reduction of slightly under 4% in solar intensity for the Late Ordovician.

    I also fail to follow your assessment of that 11% reduction of solar forcing. Perhaps you could set out a more detailed assessment.Ribas (2009) Fig 1

  8. According to this recent study we have a way more accurate view on this issue now:

    Schwark2019

    In the Hirnation Event Summary:

    "Massive perturbations of the atmospheric and hydrosphericcarbon cycle occurred with CO2concentration varying between 8-16 x PAL and near PAL over short periods of time." PAL means Present Atmospheric Level.

    This is quite remarkable, it tells us that a glaciation is capable to absorb even CO2 ammounts of 6000ppm. It does not matter how high CO2 Levels are, a glaciation will happen when the following event occurs:

    Sufficent Landmasses within the Polar Circles (LPC).

    Going through all time periods, we can show how decisive landmasses at the polar circles are. Note that the polar circles represent a very narrow area at the north and south borders on these pictures. Greenland todayis a good example as it forms the only northern ice shield, mainly being within the arctic circle, while edging Canada and Russia are not inland iced.

    Cambrian warm period, Landmasses in the Polar Circles (LPC): 0%-10%

    Cambrian

    Ordovician hirnantion glacial event antarctic LPC 100%:

    HirnantionEvent

    Silurian cold LPC antarctica 90%:

    Silur

    Devonian warming LPC 10% - 40% :

    Devon

    Carboniferus glaciation, Continents drop back to the south pole antarctic LPC: 90%-100%

    Karbon

    Permian Cold with late permian transition towards mesozoic Pangea arctic LPC 80% - 100%:

    Perm

    Triassic warming, antarctic PLC 10%-20%, arctic PLC 70% to 90%. only Southern PLC decisive? Arctic inland ice forming reversed with the jurassic? Triassic north pole contradicton.

    Trias

    Jurassic, Landmasses moved away from the arctic cycle. arctic LPC 10%-20%. antarctic LPC 5%-10%.

    Jura

    Cretateous, sea level rise noticeable, deglaciation at its maximum, transition to upcoming glacial period, Antarctica moving south. Antarctic LPC 80%-100%:

    Kreide

    Today, Cenozoic glacial period Antarctica resting at the pole once again. Greenland LPC 10% -20%, Antarctica 90%-100% LPC.

    With an Ockham attempt i want to make 3 main arguments on why CO2 is not needed and not likely to play any thermal role at all:

    1.Faint Sun Paradox,Snowball Earth and the Hot House Equilibrium.

    The faint sun paradox is not a paradox. It is another evidence of how strong the terrestial force Ice Albedo is and therefore again the continental distribution.

    Even with a 25% lesser sun, Oceans occur,hence the term "paradox".While precambrian snowball effects due to a supercontinent at the south pole, demonstrate the lesser sun effect.

    The so called paradox underlines the trumendos forcings of Albedo and it describes the fundamental drive towards a hot house equilibrium whenever the poles are uncovered by land.

    This Basic heating Trend that is strong enough to even compensate the faint sun paradox puts CO2 further away from having any thermal influence. This basic heat trend is documented by all the terminations of glacial epoches and even more so in the precambrian, with a barrier where no more heating seems possible.

    So we keep in mind that we have a Glacial period during the ordovician to the early silurian, with Co2 levels around up to 6000ppm.

    2. Carboniferous CO2 Levels

    The carboniferous marks the point where the flora takes an increased influence on CO2 levels.

    T°Co2overview

    The late devonian till the middle carboniferus show how CO2 is absorbed while temperatur takes ~90 mio years to "follow".The reason temperature goes down is as usual, the continental drift towards the south pole.

    What we eventualy see is a double decline in CO2.

    The jurassic-cretaceous meeting of CO2 and temperature speaks for itself.

    3. Today,GISS and an estimated CO2 sensitivity of 1,5°C

    The uncertenty itself on the CO2 sensitivity after 30 years of research tells us per se that the science is not settled. IPCC on a global warming of <ahref=https://www.ipcc.ch/sr15/chapter/chapter-1/>1,5°C

    "Past emissions alone are unlikely to raise global-mean temperature to 1.5°C above pre-industrial levels (medium confidence)"

    "1.5°C emission pathways are defined as those that, given current knowledge of the climate response, provide a one- in-two to two-in-three chance of warming either remaining below 1.5°C

    or returning to 1.5°C by around 2100 following an overshoot."

    GISS  actualy does show us a trend towards 1°-1,5°C ~2100 a.d. It is the natural interglacial trend. There is no evidence that our warming period is unique in its rate of warming compared to past medieval epoches

    or to the past 11 Interglacials in our ice cores

    The lowest model called the "russian model"

    What is with Planck and Bolltzmann? my guess is Lüdeckepage19
    and others are right, the saturation is already reached at PAL with 1°C

    Since the Ordovian showed how much CO2 can be absorb in the oceans, acifidication of the ocean  due to human emissions might be the bigger threat. Even though most of the CO2 was embeded in limestone, hence the CO2 "starvation".

     

    Response:

    [DB] Off-topic snipped.

  9. Nyood,

    your presentation of items is jumbled or durcheinander, as the Germans say.  It would be helpful if you could make a succinct summary of the information you wish to convey for this particular thread (and not a Gish Gallop of disparate items belonging to many different threads).

    Please note that the Ordovician sun was about 3% fainter than the modern sun.  The "25% lesser sun" belongs to the very early life of the planet Earth.

    You seem to be suggesting that atmospheric CO2 has no effect on planetary surface temperature.  But that goes against all modern science ~ but still, if you are serious in stating it, then you should present your argument in the appropriate thread here in this SkS website.

  10. Ok i will try to be more structured with future comments.

    You seem to confuse cambrian and precambrian in your criticism. The precambrian is a superaeon before the cambrian era, also called Cryptozoic. Therefore i was talking about the maximum value of a 25% dimmer sun, One of the snowball effects i refered too happend very early in the hadian, the younger double snowball event happen way closer to the cambrian.

    <a href="https://en.wikipedia.org/wiki/Geologic_time_scale"> WikiGeoTime</a>

    Yes my conclusion statement stays:

    The only thing that will cause earth to leave the glacial period of the cenozoic is when Antarctica will move away from the south pole once again.

  11. Nyood @85 , thank you for that comment: <"The only thing that will cause earth to leave the glacial period of the cenozoic is when Antarctica will move away from the south pole once again.">

    I think it is not controversial that Earth will remain in an ice age for a very long time (ice age defined as Earth having substantial ice at one or both poles).

    Even during the warm Eemian period, there was polar ice in the Scandinavian region (at least) plus the huge amount of land ice on the Antarctic continent.

    A small rise in temperature (from today's) might fully melt Greenland ~ but that would likely take  >1000 years.   Still, most of the East Antarctica ice sheet will survive.

    There are two scenarios where Antarctic ice will disappear:-  (A) the very long term (many millions of years) as the solar output continues its gradual increase, and (B) an unexpected Large Igneous Province eruption of CO2, such as the Siberian or Deccan events.  In either of these circumstances, the South Polar ice would disappear, even if Antarctica did not move from its present polar position.

    The present day crisis involves the small-magnitude warming which will displace around 200 millon people as sea level rise approaches 1 metre [Kulp & Strauss, 2019].  And probably a much greater size of refugee problem, coming from storm surge, land salination, and other agricultural adverse effects (including low-humidity and high-humidity heat waves].

    All this, within the lifetime of children born in 2019.

  12. "There are two scenarios where Antarctic ice will disappear:
    - (A) the very long term (many millions of years)
    as the solar output continues its gradual increase, and
    (B) an unexpected Large Igneous Province eruption of CO2,
    such as the Siberian or Deccan events. In either of these
    circumstances, the South Polar ice would disappear, even if
    Antarctica did not move from its present polar position."

    (A) This is true the sun will warm for a billion years. If and
    when this will melt the poles i do not want to discuss
    here,interesting question towards the HHE Hot House Equilibrium though.

    (B) The Deccan Traps caused cooling. wikiDeccan
    The polar ice would not disappear, you just make an assumption here. The ordovician
    tells us the opposite: Even with levels of 6000ppm a glaciation occurs.
    You miss the start of my original post: "This is quite remarkable, it tells us
    that a glaciation is capable to ABSORB even CO2 ammounts of 6000ppm"
    and you ignore the core of my LPC theory, basicly by just saying "it is so, Antarctica would melt"

    Please be more carefull with prospective criticism, you can try to go on and find
    other arguments pro CO2, like the PETM or the permian-triassic in the past to stay on topic.
    Or you can fight my theory and i give you a hint here: i mentioned the "triassic north pole paradox".

    "The present day crisis involves the small-magnitude warming which will displace around 200 millon people
    as sea level rise approaches 1 metre [Kulp & Strauss, 2019]. And probably a much greater size of refugee problem,
    coming from storm surge, land salination, and other agricultural adverse effects
    (including low-humidity and high-humidity heat waves]."

    What you are doing here is seen very often, you let someone speak for you.
    I would have to read the study, check the sources, check the context
    and then come back to you. You have to express your thoughts yourself and use studies to back up your argumentation.

    First of all what we are seeing here is the common axiomatical acception that CO2 plays a strong role, i would have to argue with Strauss
    and confront him with my LPC theory first.
    You can check accepted sources like NASA on Sea rise. It will never be that quick that men will not adept let alone react in time.
    Furthermore since i see the increase as natural, there is no point to try to change it.

    Response:

    [DB]  Please re-read the entire post before commenting.  As the post notes, CO2 is not the only driver of climate.  No climate scientist makes any such assertion.  So you tilt at windmills of your own building.

    Relevant to this discussion:

    "The evolution of Earth’s climate on geological timescales is largely driven by variations in the magnitude of total solar irradiance (TSI) and changes in the greenhouse gas content of the atmosphere.

    Here we show that the slow ∼50 Wm−2 increase in TSI over the last ∼420 million years (an increase of ∼9 Wm−2 of radiative forcing) was almost completely negated by a long-term decline in atmospheric CO2. This was likely due to the silicate weathering-negative feedback and the expansion of land plants that together ensured Earth’s long-term habitability.

    Humanity’s fossil-fuel use, if unabated, risks taking us, by the middle of the twenty-first century, to values of CO2 not seen since the early Eocene (50 million years ago).

    If CO2 continues to rise further into the twenty-third century, then the associated large increase in radiative forcing, and how the Earth system would respond, would likely be without geological precedent in the last half a billion years."

    Foster et al 2017 - Future climate forcing potentially without precedent in the last 420 million years

    Foster Figure 2

     

    Off-topic and inflammatory snipped.

  13. Nyood @87 , my apologies to you, for my speaking overly-briefly about LIP eruptions.

    My example of the Siberian Traps event demonstrated the vast release of CO2 and consequent high temperature rise on Earth.  The Deccan Traps event was smaller in effect, and also was complicated by the cooling effect of the Chicxulub asteroid impact.

    You are quite right to say LIP events can have a transient cooling effect from the venting of sulphate & other aerosols . . . and also in the much longer term, the exposed silicate rock does gradually draw down the atmospheric CO2 (and hence the lower CO2 will lead to a global cooling, relative to what had gone before).

    My essential point with respect to Antarctica, was that a future LIP eruption could be of enough size to produce a major boost in atmospheric CO2 and consequently a major temperature rise for a lengthy period ~ sufficient to melt away the huge Antarctic ice sheet.

    We must hope that a major LIP eruption will not occur, for its result could be catastrophic.

    The question of Ordovician temperatures and glaciation is a difficult one, for the timing of events & CO2 changes rests presently on low-resolution data.   For the relevance to the climate of the modern age, we must rely heavily on the lessons from basic physics.

    Response:

    [JH] Links activated.

    For future reference, when you include a link in a post, please activate it by using the "Insert/Edit Link" feature of the Edit Box.

  14. Moderator Response:

    "[DB] Please re-read the entire post before commenting. As the post notes, CO2 is not the only driver of climate.
    No climate scientist makes any such assertion. So you tilt at windmills of your own building."

    There seems to be a  missunderstanding here, apologies for my bad writing in my initial post if this is the reason for the confusion.

    I do not contest that or if CO2 is a sole climate driver. I state that CO2 is no driver at all.

    So let me try to give a summary here again:

    The theory is radical. The two equilibriums glacial period (high landmass ratio within polar circles,high LPC) vs Hot House Effect (HHE),
    are that dominat, they neglect all other drivers. low LPC will result in a HHE no matter what.
    General backround HHE forcing is so effective, all other factors do not matter, the warming rate is always rapid, the transition is always within 100 mio years.
    The second largest factors that still have significant forcing are all factors that relate to albedo foremost ice albedo (dust, ashes, sea level).

    Following Orckham we have several situations where neglecting CO2 makes way more sense than assuming any significant forcing.

    Ordovician high disparity of CO2 and T. Carboniferus CO2 drop way before temperature (T) drop. Jurassic CO2-T meeting. Cretaceous all time highest discrepancy.

    TempCo2History to

    The situations where an explanation for CO2 is needed to justify its assumed forcings, is simply and higly objected by Orckham`s razorblade principle.

    So politely i have to say dito: Please re-read my initial post.

    Response:

    [PS] This is heading way into sloganeering territory. You are selecting only observations that support your ideas and ignoring completely all others. Science does not operate that like. You cannot ignore measured increase in downwelling radiation, conservation of energy, nor explain past climate change with hand-wavy statements that violate physics. If you have a theory that can match all observations, simpler and with better precision than current theory and concordant with laws of physics then by all means publish. Meanwhile, current climate theory is the one that matches Occams razor. No more half-baked sophistry please.

  15. Nyood, the importance of CO2 as a driver of climate, is supported by (A) theoretical calculations [Arrhenius and later scientists]; is supported by (B) experimental evidence; is supported by (C) observational evidence; and is supported by (D) geological evidence.  In other words, the mainstream science developed during the past 200 years.

    The principle of Occam's Razor is a often a helpful guide to thinking : it is not in itself evidence and it is not in itself a method of proof.

    Ockham (or Occam) did not support the cutting off or ignoring of evidence.  Newton and Einstein did not ignore evidence.   Nyood, why do you choose to ignore evidence?

  16. Nyood @89,

    You ask that we roll back to your initial comment here, up-thread  @83 where you begin by quoting from a talk by Schwark & Bauersachs [slides] quoting from its summary:-

    "Massive perturbations of the atmospheric and hydrospheric carbon cycle occurred with CO2 concentration varying between 8-16 x PAL and near PAL over short periods of time." (PAL = Present Atmospheric Level.)

    From this you conclude the following:-

    "This is quite remarkable, it tells us that a glaciation is capable to absorb even CO2 ammounts of 6000ppm. It does not matter how high CO2 Levels are, a glaciation will happen when the following event occurs:"

    Your conclusion is incorrect on a number of levels.

    (1) The total climate forcing from 6000ppm CO2 is very roughly 40Wm^-2. There is no evidence to suggest that climate was impacted by such forcings (from any source) during the Ordovician.

    (2) According to your cited reference (slides 11 & 14), the period with elevated CO2 significantly above 4000ppm coincides with the Katian, a period of warming.

    (3) The period following the Katian sees falling CO2 and falling temperature. The period of high glaciation during the Himantian sees CO2 estimates dropping to perhaps 1500ppm. Relative to our recent ice ages with 180ppm CO2, the Himantian CO2 forcing would thus be perhaps +11Wm^-2 while the relative solar forcing would be -8Wm^-2.

    (4) Your assertion @89 is that the major forcing of climate is the tectonic positioning of land over polar regions. Yet there was such land over polar regions throughout the Ordovician when these great swings of climate appear suggesting the climate was being forced by entirely different mechnisms.

    I would therefore suggest you have failed to provide any support for your assertion "CO2 is no driver at all."

  17. "(1) The total climate forcing from 6000ppm CO2 is very roughly 40Wm^-2. There is no evidence
    to suggest that climate was impacted by such forcings (from any source) during the Ordovician."

    (1) The first sentence is axiomaticly using an estimated forcing of CO2 and therefore is a statement, though the consequences you state are true (none).
    I state that CO2 forcing is max 1°C, reaching saturation with roughly PAL levels, pretty much always or already.

    The Second sentence is true, the forcings that Do determine climate Temperature (T) are the two equilibrium forces
    hothouse effect (HHE) and high landmass ratio within polar circles (LPC).
    The faint sun paradox (FSP) underlines the strength and dominance of the terrestial forcings by allowing
    the orrdovician-silurian events, HHE - LPC - HHE, to happen within the same T amplitude of all compareable HHE and LPC events untill today.
    Neglecting CO2 and reducing the FPS or -4% TPI, in its forcings.

    On top of that you devaluate some of your own arguments brought up in the coming sections. According to (1) you do not allow yourself any comparison from there on.

     

    "(2) According to your cited reference (slides 11 & 14), the period with elevated CO2 significantly above 4000ppm
    coincides with the Katian, a period of warming."

    (2)This sentence has no expressiveness. HHE is happening anyways before and after the LPC.
    The Katian documents the late transition state towards an LPC, in fact it doubts CO2 as a driver.
    The discrepancy between assumed CO2 forcing and T is underlined by the general high CO2 level in the atmosphere, the planet will reach a glaciation from here on, to develop extreme ice shields despite CO2 levels this high. The FPS is solved as mentioned.
    Furthermore forces mentioned in the Schwarck study explain the Katian warming already:
    " Bodaevent:
    Continental Flood Basalt Province.Alternatively to a bolide impact, LIPs have been postulated as warming triggers."

    The forcing here that matters is Ice albedo reduction due to dust and ashes.
    We can see this again when younger impacts and events causie warming rather then cooling.
    An accumulation of dust and ashes at the poles are the result of a rather quickly cleanse of the atmosphere.

     

    "(3) The period following the Katian sees falling CO2 and falling temperature.
    The period of high glaciation during the Himantian sees CO2 estimates
    dropping to perhaps 1500ppm. Relative to our recent ice ages with 180ppm CO2,
    the Himantian CO2 forcing would thus be perhaps +11Wm^-2 while the relative solar forcing would be -8Wm^-2."

    (3) "dropping to perhaps 1500ppm". The Schwarck study claims PAL up to x6 till x20. Please specify "perhaps"
    and clarify why it is not PAL but minimum PAL x3 according to you. Where are Schwank et.al wrong ?

    Reminding here that the level of CO2 does not matter in the first place unless it is below PAL (max -1°C), using my axioms.

    Again you apply axiomatical values, which are not needed to explain temperatures, you are still using the FSP as a theory support, or to bring it in an equilibrium with
    CO2 forcing, by trying to "ramp up" CO2 to a minimum of 1500ppm. Ironically this opposites many attempts
    that try to lower CO2 to explain why a glaciation happens, despite ~6000ppm before and after the glaciation, in the first place. These views higlight the needs to explain CO2 forcings as assumed (too high).

     

    "(4) Your assertion @89 is that the major forcing of climate is the tectonic positioning of land over polar regions.
    Yet there was such land over polar regions throughout the Ordovician when these great swings of climate appear suggesting
    the climate was being forced by entirely different mechnisms.

    I would therefore suggest you have failed to provide any support for your assertion "CO2 is no driver at all." "

    (4)This is partly true, as strong as it is the Ice has to build up, which happens very quickly in the hirnation, after the Bodaevent.
    The middle to late ordovician is in transition, the continental drift towards the pole is remarkable.
    Which is documented with the Silurian:

    Ordovizium

    Silur

    Furthermore one has to take in account the varying lengths of time periods. The ordovician has been added historicaly,
    it was included in the silurian before, therefore this interesting periods are "staunched".

    Antarctica shows a trend towards having a "drop back" to the south pole, mentioned in the devonian and possible in the jurassic.
    Maybe this happened here too and we need more accurate paleogeorgraphic data.

     

    Answering two other comments here made by other users:

    89.Moderator response:

    "[PS] This is heading way into sloganeering territory. You are selecting only observations that support your ideas and ignoring completely all others. Science does not operate that like.
    You cannot ignore measured increase in downwelling radiation, conservation of energy, nor explain past climate change with hand-wavy statements that violate physics.
    If you have a theory that can match all observations, simpler and with better precision than current theory and concordant with laws of physics then by all means publish. Meanwhile,
    current climate theory is the one that matches Occams razor. No more half-baked sophistry please."

    My theory already has a better explanation with its radical attempt, that is the whole point. This is not "sloganeering" it is just a very radical attempt so it asks for situations where we have evidence that show CO2 as a significant driver, relating to topic.
    I understand that my radical attempt makes it easy for me but i have to insist on the fairness that i am allowed to show that radical assumptions that i made, make more sense then your axiomatical assumptions.
    There is the inherit problem that we eventualy go off topic but i have to ask you at this point which laws and forcings (radiation, energy conservation) are ignored by me in which way ?
    I ignore factors as far as they allow me, hence ockham.
    I insinuate that your axioms make less sence then mine. Your critisicsm lacks precission at this stage, when it comes to why my radical assumptions are not allowed and where they are not concordant with laws of physics.

     

     

    90. Eclectic:

    "Nyood, the importance of CO2 as a driver of climate, is supported by (A) theoretical calculations [Arrhenius and later scientists]; is supported by (B) experimental evidence; is supported by
    (C) observational evidence; and is supported by (D) geological evidence. In other words, the mainstream science developed during the past 200 years.

    The principle of Occam's Razor is a often a helpful guide to thinking : it is not in itself evidence and it is not in itself a method of proof.

    Ockham (or Occam) did not support the cutting off or ignoring of evidence. Newton and Einstein did not ignore evidence. Nyood, why do you choose to ignore evidence?"

    (A) Arrhenius,Planck Feldmann et.al give a frame, it is known that we can not apply CO2 with a clear value (uncertainty). This leads to a Saturation and or Lindzen et.al and therefore inevitable offtopic, as much as i am willing to discuss it.

    (B) same as (A)

    (C) I clame that observational evidence support my theory today: Dramatic CO2 increase with a moderate warming trend. My initial post was rightfully snipped of modern time references as offtopic.

    (D) Geological evidence is the core of the LPC theory.

    Response:

    [DB] Off-topic, sloganeering and inflammatory snipped.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts, ignores the refutations of others (sloganeering) or simply makes things up. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.  The point of commenting is to further the understanding of the science, using credible evidence and citations to credible sources.  Much of what you are attempting to do would be better-placed on other threads (many exist).  Blanket asserting that the greenhouse effect is not well-documented, well-researched and well-understood is an own-goal and a waste of everyone's time.
     
    Finally, please understand that moderation policies are not open for discussion (complaining about moderation that everyone else has little to no issues with rather than simply adhering to the Comments Policy likewise wastes everyone's time).  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  18. Nyood: "I state that CO2 forcing is max 1°C, reaching saturation with roughly PAL levels, pretty much always or already."

    Earlier you said "The total climate forcing from 6000ppm CO2 is very roughly 40Wm^-2"

    That would suggest then that a 40w/sq.m forcing would produce only a 1 deg C change? What published work is this based on? How did you get the 40 W/sq.m value?

    What is your basis for claiming "reaching saturation with roughly PAL levels, pretty much always or already."

    Current forcings are calculated from radiative physics, Iacono and Clough, and many others have worked on that. So what do you mean by "CO2 forcings as assumed (too high)"? AFAIK, these forcings are not assumed, they are calculated on the basis of the physical properties of the gas.

    Response:

    [PS] "And these forcings are not assumed, they are calculated". And directly observed https://www.nature.com/articles/nature14240. ie observations match theory. By contrast we are seeing wild claims from Nyood with no supporting evidence.

    Argument about CO2 saturation belong in this thread. If nyood wants to make that claim, then present the evidence in that thread please.

  19. Nyood

    continuing with my itemized points of post #90 and your itemized replies in post #92 (subsection) :-

    (A)  Your quote: <" ... can not apply CO2 with a clear value (uncertainty)">

    Here, too much is lost in translation.  You will need to make a re-translation of your idea into English, to achieve a meaningful statement.   Secondly: "Saturation" is invalid, and "Lindzen" is (often) invalid.

    (B)  <"(B) same as (A)">  does not make sense as a reply.

    (C)   <"observational evidence support my theory today">   Yes, but only in part. The full picture of observational evidence (on CO2 greenhouse) renders your theory invalid [ungueltig].

    (D)  Geological evidence supports your theory only in part.  The full picture of geological evidence renders your theory invalid.

    Nyood ,

    in my post #90 , the final and most important question (for you) was: "why do you choose to ignore evidence?"  Note the word choose  [waehlen].

    You have not answered that question.  Please do so, carefully and thoughtfully.  It requires using insight [Einblick; Selbstverstaendnis].

  20. nyood @92,

    (1a) To present a value for CO2 forcing without providing evidential support is not axiomatic, either in the sense of it being self-evident or (probably in the sense you intend) unquestioningly-evident. The evidence can be presented should you so wish and, uncontroversially beyond-question, it is correct.

    You yourself present @92 an unsupported evaluation of CO2 forcing, providing a maximum value which appears novel and controversial in the extreme. You fail to present any evidential support which in the circumstance is turning this discussion into a pantomime. Perhaps you could correct the untenable postion you create for yourself by providing that missing evidence.

    (1b) Your confused statements regarding HHE/LPC appear to contrdict the geographical situation as commonly understood, in that the "Land mass" Gondwawa sits static over the "Polar Circle" throughtout this period. You need to consider how it is your LPC appears then disappears within this period when the contition you say causes LPC remains unchanging?

    (2) Your cut-&-paste from the Schwark & Bauersachs slides appears particularly inept as support for your assertion "in fact it doubts CO2 as a driver." If you, for instance, examine Slide 11 you will see your assertion is fundamentally contradicted.

    (3) Here you really do dip into uncomprehensibility. Do note that the Schwark & Bauersachs slides do not ever say CO2 dropped to present atmospheric levels 400-odd million years ago. The statement you misread from Slide 23 says purely that CO2 varied "between 8-16 x PAL and near PAL." The value 1500ppm can be taken from their Slide 11.

    (4) If it is not land at the polar circle that creates your LPC condition; if it is ice-covered land, you do then reqire to explain the forcing that allows the growth/shrinkage of that ice. And in doing so, your theory now lacking the tectonic element, do consider that you are now describing a climate feedback not a climate forcing.

  21. @MA Rodger

    (1a) "To present a value for CO2 forcing without providing evidential support is not axiomatic,
    either in the sense of it being self-evident or (probably in the sense you intend) unquestioningly-evident.
    The evidence can be presented should you so wish and, uncontroversially beyond-question, it is correct.

    You yourself present @92 an unsupported evaluation of CO2 forcing, providing a maximum value which appears novel and controversial in the extreme.
    You fail to present any evidential support which in the circumstance is turning this discussion into a pantomime.
    Perhaps you could correct the untenable postion you create for yourself by providing that missing evidence."

    (1a) The evidence that i imagine you would provide, will all result in the question: What is missing? This is manifested in the fact that you will get no exact value for CO2 sensitivity, despite known elemental spectral laws regarding infrared absorption. In other words: We are still estimating with 1,5°C - 4,5°C per doubling (?).

    The theory that CO2 reaches a "saturation" already, is just the most likely aproach to me. However the forcings of HHE/LPC could be even that strong
    that they shrink down all other factors making them neglectable, not "needing" any other explanation to temperature.

    The major evidence i can deliver here is the fact that the so called saturation for each GHG is one of the known unkwons and that there are countless debates
    on this issue, underlining how unsolved this whole matter is.

     

    "(1b) Your confused statements regarding HHE/LPC appear to contrdict the geographical situation as commonly understood,
    in that the "Land mass" Gondwawa sits static over the "Polar Circle" throughtout this period.
    You need to consider how it is your LPC appears then disappears within this period when the contition you say causes LPC remains unchanging?"

    (1b)  I see no contradiction, in my former post i gave you the 2 links with the continental distribution, matching my theory.(Ordovizium, Silur)

    I see what you are getting at though wih Schwanck slide 11: The pictures with the "paleo glacial reconstruction". They use a static continental distribution here. It is more likely that the continents were merging towards the hirnation. In a larger perspective the continents definetly move  towards the pole, documented by the ordovician with the silurian as a whole. The ice needs to build up and the Boda event interrupted the glaciation process by reducing ice albedo.

     

    "(2) Your cut-&-paste from the Schwark & Bauersachs slides appears particularly inept as support for your assertion "in fact it doubts CO2 as a driver."
    If you, for instance, examine Slide 11 you will see your assertion is fundamentally contradicted."

    What is contradicted here? Slide 11 shows the Boda event and its CO2 emissions, the CO2 does not matter to me, regarding temperature, the factors that matter are albedo reducing ashes and dust.

    If you are refering to this sentence on page 11: "atmospheric emission of large amounts of CO2 and subsequent climate warming, and.."

    Then i can only tell you that Schwarck et.al are using the neglectable CO2 sensitivity axiomata here. The reason why the Katian doubts ´CO2 as a driver´ is because it marks, with all other epoches preceeding the LPC event, the time where CO2 fails to work as assumed. Where should it show its significant forcing if not here?

     

    "(3) Here you really do dip into uncomprehensibility. Do note that the Schwark & Bauersachs slides do not ever say CO2
    dropped to present atmospheric levels 400-odd million years ago.
    The statement you misread from Slide 23 says purely that CO2 varied "between 8-16 x PAL and near PAL."
    The value 1500ppm can be taken from their Slide 11."

    (3) Well, it does not matter to me, if you want it can be 1500ppm, i would not consider that close to PAL though. PAL would just makes sense to me since the ordovician

    is compareable to all other LPC events.

    Near Pal makes sense to me because it would reach common glacial CO2 levels. I have not enough knowledge of solubility.

    Near Pal is enough for me to support the theory when it comes to: All equilibrium events and the transitions inbetween happen in the same fashion, despite varying CO levels.

    "(4) If it is not land at the polar circle that creates your LPC condition; if it is ice-covered land,
    you do then reqire to explain the forcing that allows the growth/shrinkage of that ice.
    And in doing so, your theory now lacking the tectonic element, do consider that you are now describing a climate feedback not a climate forcing."

    The factor that you are missing here is indeed a fundamental one. It is the fact that snow will not accumulate ice sheets on the sea.
    The double proof for this is the arctic sea, with Greenland within the polar circle.

    In fact with your misunderstanding here it makes me wonder if continental drift as a time dependet factor is included in the prognostications and not only be representd by the, in itself correctly implemented, ice albedo.

    In other words:Fundamently excluding a long term factor of warming.

    Response:

    [DB] The topic of this post is the skeptic claim that "CO2 was higher in the past" (which says nothing about why CO2 levels are high today).  It is not about climate sensitivity or CO2 levels being saturated.  Further, you really need to start citing credible sources appearing in the peer-reviewed literature to support your claims.  This is not optional.

    Simply making things up based on your lack of understanding of the topic means that you pre-concede the scientific portion of the discussion and tacitly admit that you are just venturing your opinions on a topic that you demonstrably lack understanding of and that you have not read the threads on the topics on question.

    Off-topic and sloganeering again snipped.  Those wishing to respond to those snipped points, please do so at a more appropriate thread and link back here.

  22. I want to subsequently deliver a source that confirms what i said with: "Snow will not accumulate ice sheets on the sea"  and therefore is crucial to my theory:

    fuBerlinContinentaldrift

    To not falsify anything with my own translation, i google translated this middle part:

    "Ice ages seem to occur only when there is a larger land mass at least at one geographic pole. Snow has to lie on the continents and not fall into the water, so that a snowpack can form in relatively high latitudes and ice can form over time. Once this is the case, positive ice-albedo feedback occurs due to the high positive albedo values of snow and ice, and further cooling occurs."

     

    Response:

    [DB]  As land-based ice sheets grow (due to snowfall gains in their expanded accumulation zones), sea levels fall.  Land-based ice flows towards the continental edges and extends out over the ocean in the form of ice shelves.  Where sea ice forms next to the ice shelves, snow accumulates, both on the ice sheets, the ice shelves and on sea ice.  This point of argumentation is not germane to the topic of this post.  Please stay on-topic.

    Note that a website by itself is not considered part of the primary literature, especially if it does not belong to a primary producer of research information, such as NOAA, NASA or the like.

  23. Noting that atmospheric CO2 levels have been falling since the Jurassic period and was approaching a level that some scientist claim cannot support plant life (150 ppm)...Is it possible that mankind has evolved to SAVE the living planet instead of DESTROY it? Of course, we may well bring about our own distruction and most of the animal life on the planet...But wasn't the earth headed for a cold death? Carbon and oxygen has been locked away in carbonaceous sedimentary rock, coal, oil, and methane gas. Alas, along comes man to extract all that carbon and oxygen from the ground and breathe new life into a dying planet. 

    What are your thoughts? Am I way off base? (I honestly mean no harm and I certainly do not want to start an angry debate...It has just been a curious thought of mine for over twenty years).

  24. Livinginawe,

    You are way off base.  The world was doing fine before humans evolved.  Wiping out a large percentage of all living creatures (both animals and plants) does not count as "saving" the planet.

    Read some of the historical accounts of how much life existed before humans came to a location.  They describe so many fish on the Grand Banks fishery that ships were slowed by running into them and they could be scooped up in baskets from the surface.  There were so many whales in the Gulf of St. Lawerence that the noise of them breathing at night made it difficult for sailors to sleep.

    Life adapts to slow changes.  The problem with AGW is that the change is way to fast for life to evolve (in addition to the many other harmful pollutants humans release).

  25. LivinginAwe @98

    The plants have already adapted to the long term decline of CO2 in earth history. This is why grasses and other C3 type plants evolved. The most sturdy plants are believed to be able to deal with even 50ppm.

    Eventualy all CO2 should be stored in primerly limestone, yet the decline is very steady and it will take many more million years to completly deplete all CO2 if that ever happens. After our ice age, when Antarctica moves away from the pole again, which is expected to happen in ~90 mio years, the ice age will end and the warming oceans will release the "rest" of the CO2 that is still held by them (1000-2000 ppm).

    My take on this is that earth has already experienced these situations, there is a barrier when it comes to warming that saves us from overheating and there is also a barrier when it comes to cooling and CO2 declining that saves life.

    So in a way you are right, CO2 might help our plants and the greening effect is already documented by Nasa, but we do not know how the plants will deal with this sudden increase of CO2 made by us.

    Response:

    [DB]  "CO2 might help our plants and the greening effect is already documented by Nasa"

    According to the most recent research, the Earth stopped getting greener 20 years ago:

    "the vegetation greening trend indicated by a satellite-derived vegetation index (GIMMS3g), which was evident before the late 1990s, was subsequently stalled or reversed"

    Note that this 2019 research paper was published AFTER the 2016 NASA article on that topic and contains later information.

    Further discussion here:

    "The study published yesterday in Science Advances points to satellite observations that revealed expanding vegetation worldwide during much of the 1980s and 1990s. But then, about 20 years ago, the trend stopped.

    Since then, more than half of the world’s vegetated landscapes have been experiencing a “browning” trend, or decrease in plant growth"

    Further discussion of such is off-topic for this thread, but can be pursued here, "CO2 is plant food".

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