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CO2 levels during the late Ordovician

Posted on 12 March 2010 by John Cook

One argument used against the warming effect of carbon dioxide is that millions of years ago, CO2 levels were higher during periods where large glaciers formed over the Earth's poles. This argument fails to take into account that solar output was also lower during these periods. The combined effect of sun and CO2 show good correlation with climate (Royer 2006). The one period that until recently puzzled paleoclimatologists was the late Ordovician, around 444 million years ago. At this time, CO2 levels were very high, around 5600 parts per million (in contrast, current CO2 levels are 389 parts per million). However, glaciers were so far-reaching during the late Ordovician, it coincided with one of the largest marine mass extinction events in Earth history. How did glaciation occur with such high CO2 levels? Recent data has revealed CO2 levels at the time of the late Ordovician ice age were not that high after all.

Past studies on the Ordovician period calculated CO2 levels at 10 million year intervals. The problem with such coarse data sampling is the Ordovician ice age lasted only half a million years. To fill in the gaps, a 2009 study examined strontium isotopes in the sediment record (Young 2009). Strontium is produced by rock weathering, the process that removes CO2 from the air. Consequently, the ratio of strontium isotopes can be used to determine how quickly rock weathering removed CO2 from the atmosphere in the past. Using strontium levels, Young determined that during the late Ordovician, rock weathering was at high levels while volcanic activity, which adds CO2 to the atmosphere, dropped. This led to CO2 levels falling below 3000 parts per million which was low enough to initiate glaciation - the growing of ice sheets.

Last week, another study headed by Seth Young further examined this period by extracting sediment cores from Estonia and Anticosti Island, Canada (Young 2010). The cores were used to construct a sequence of carbon-13 levels from rocks formed during the Ordovician. This was used as a proxy for atmospheric CO2 levels, at a much higher resolution than previous data. What they found was consistent with the strontium results in Young 2009 - CO2 levels dropped at the same time that sea surface temperatures dropped and ice sheets expanded. As the ice sheets grew to cover the continent, rock weathering decreased. This led to an increase in atmospheric CO2 which caused global warming and a retreat of the glaciers.

Thus arguments that Ordovician glaciation disproves the warming effect of CO2 are groundless. On the contrary, the CO2 record over the late Ordovician is entirely consistent with the notion that CO2 is a strong driver of climate.

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Comments 51 to 87 out of 87:

  1. If we continue to release CO2 to the atmosphere, at what point will the CO2-greenhouse effect saturate (that is, the point at which all the IR in the CO2-absorbed wavelenghts is absorbed, so that any further CO2 concentration increase will have no effect on greenhouse effect)? 1000 ppm? 2000 ppm? 10 000 ppm? By the way, is Venus already CO2-saturated in the CO2 wavelenghts?
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  2. The thing to understand about saturation is that there is always an altitude above which the absorption is not saturated. That altitude goes up with overall concentration of course. The temperature at that altitude goes up as the concentration goes up. But that means the temperature at every level below that altitude also goes up (search on "atmospheric lapse rate").
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  3. I just realized one could misread my third sentence. Replace with "The temperature at a fixed altitude near the saturation threshold altitude goes up as the concentration of CO2 and the saturation threshold altitude both go up.
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  4. From Peru (#51), according to the IPCC (AR4) climate models the radiative forcing due to CO2 has a logarithmic relationship to global temperature. Thus using your numbers and taking today's conditions as a starting point the relationship between CO2 and global temperature should look like this: 1,000 ppm add 2.5 Celsius 2,000 ppm add 4.4 Celsius 10,000 ppm add 8.8 Celsius While most scientists accept that CO2 has a significant effect some believe that the IPCC exaggerated the scale. For example, Lindzen & Choi (2009) suggest that the radiative forcing is six time weaker than the IPCC says. If L&C09 is correct you can divide the above temperature increases by a factor of 6. The Venusian atmosphere is ~97% CO2 (970,000 ppm). If our atmosphere had the same composition one would expect temperatures to be ~21 Celsius higher than today assuming the IPCC is right. Please note that I am a physicist rather than a climate scientist so the real experts may dispute my numbers!
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  5. The greenhouse effect has nothing to do with the heat conductivity - nothing to do with the change due to increase in CO2 concentration. A saturation does not exist. Under saturation, some understand that on the surface of the earth emitted photons hardly reach the universe - but there is strongly absorbed which is also strongly emitted. Instead of reaching the ground than other photons emitted photons the universe - what does that have to do with saturation? With increasing concentration of greenhouse gases is changing the pressure and temperature of the Earth's tropopause increasingly in the direction of Venus and Mars tropopause. The column pressure of CO2 in the Earth's tropopause is approximately 0.11 mbar - this is comparable to the pressures of the Venus and Mars tropopause, which are almost pure CO2 atmospheres. Sincerely,
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  6. gallopingcamel, the often used aproximate relationship between forcing F and CO2 concentration is F(W/m^2)=5.35*ln(C/Co) and the temperature increase DT is proportional to the forcing DT=l*F where l is the climate sensitivity. So you get: DT=5.35*l*ln(C/Co) if you take Co as the current value (380 ppm) and a climate sensitivity of l=0.8 K/(W/m^2) you get different numbers. Anyway, the linear aproximation between DT and F cannot be pushed as far as 10000 ppm.
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  7. gallopingcamel ... L&C (2009) was quite thoroughly shot down in a follow-on paper in GRL. And elsewhere ... The best part of the story is how they cherry-picked snippets of data to fit their conclusion, though the bit about using model results that didn't include all changes in forcing to "disprove models" is a close second IMO (the model results they used had been generated to explore response to SST changes only). If they're going to complain that coupled atmosphere-ocean GCMs are giving incorrect results, one would expect them to actually *compare* with such results, wouldn't one? James Annan was quick to pick up on that point. I'm curious, is there any reason you read L&C (2009) in isolation? Or did you simply pick up a summary from one of the usual denial sites?
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  8. dhogaza (#57), the trouble with the climate models is that they are doing a really poor job thus far. L&C09 is simply the latest experimental information available and it provides a plausible explanation for the failure of climate models generally. Over the next few years satellite measurements will continue to accumulate and the error bars will shrink. Let's talk again when better information is available. With regard to the link that you kindly provided, the folks who "shot down" L&C09 hardly inspire confidence; RealClimate as a whole fails the objectivity test (unlike this fine web site). Riccardo (#56), Thanks, I stand corrected. I agree that radiative forcing calculations are simplistic when applied to high concentrations or atmospheres that have vapors present (e.g. water or sulphuric acid).
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  9. gallopingcamel, the calculations of the forcing takes into account just CO2 but the sensitivity includes feedbacks, e.g. water vapour. Not included are other forcings, natural or related to human emissions, e.g. aerosol, CH4, etc. As per L&C09 paper, they didn't prove any model wrong given that they used the wrong ones. You cannot pull a wheel out from a car and claim it isn't good. Although my analogy is definitely crude, this is more or less (one of?) the mistake in that paper. Please avoid personal opinions on anyone, scientist or commenter, and stick to their science instead.
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  10. RE#58 gallopingcamel: Can you please support your claim that climate models "are doing a really poor job thus far."? L&C09 is hardly a silver bullet. You say: With regard to the link that you kindly provided, the folks who "shot down" L&C09 hardly inspire confidence; RealClimate as a whole fails the objectivity Well it didn't take me long by google to actually find the paper that TFOW wrote (in press at the time RealClimate mention it) which is now available through Geophysical Letters. So unless you want to debate the whole peer review process...
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  11. yocta (#60), The peer review process is not a big issue for me. It suffers from the faults and failings of most human endeavors; it should be no surprise that plenty of peer reviewed papers prove to be wrong. For example almost every paper supporting AGW is contradicted by some other paper. They can't all be right. Take the paper at the head of this thread, Royer 2006 and updates such as Royer 2010. You can find a direct rebuttal at: http://www.phys.huji.ac.il/~shaviv/ClimateDebate/RoyerReply.pdf If the experts can't agree and big money is at stake the general public has to figure out who makes the most sense.
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  12. gallopingcamel:
    With regard to the link that you kindly provided, the folks who "shot down" L&C09 hardly inspire confidence; RealClimate as a whole fails the objectivity test (unlike this fine web site).
    So your objection boils down to an ad hominem (ad sitium?) attack on Real Climate, rather an attack on the arguments made by those who shot down L&C 09. Figures. And Riccardo repeats exactly what I pointed out before:
    As per L&C09 paper, they didn't prove any model wrong given that they used the wrong ones.
    They're essentially arguing that models developed for a totally different purpose prove that the coupled GCMs are wrong. That's like claiming that the low scores typical of soccer matches disprove predictions that professional US basketball teams average about 100 points a game! It's a different game! They're different models! If you are going to defend this, then there's not much reason to converse with you. My guess is that you didn't bother to read the rebuttal at Real Climate, nor the paper itself linked to by yocta. It's fingers-in-the-ears la-la-la L&C09 might be right all they way, eh?
    For example almost every paper supporting AGW is contradicted by some other paper. They can't all be right.
    This statement isn't true. And those that do are typically garbage. G&T claiming that CO2 can't warm the planet because this would violate the 2nd law of thermodynamics. L&C09 cherry picking data then comparing it with models of type A claiming that this proves that models of type B are wrong.
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  13. dhogaza (#57), the trouble with the climate models is that they are doing a really poor job thus far.
    And this statement is simply incorrect. They do a very good job of recreating paleoclimate scenarios, more recent events like cooling due to Pinatabu (done as a *prediction*, not hindcast), ENSO-like events arise as emergent properties of the major models, etc etc. NASA recently publicized the fact that water vapor feedbacks at various altitudes and with various temperature change scenarios, as measured by the AIRS sensor on the Aqua satellite, matches model predictions for such scenarios. In detail. On and on and on. Model validation efforts do *not* support your contention. And, of course, as far as the fact that we don't see monotonic increases in temperature, but rather a signal with considerable noise, is also consistent with individual model runs that show exactly the same kind of behavior. Again, on and on and on ...
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  14. Another well-known example of a causality relation going both ways: A child on the back seat of a car can cause an accident. An accident of the back seat of a car can cause a child.
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  15. 38.dhogaza at 16:39 PM on 13 March, 2010 The temp reconstruction is very similar to the one shown in the paper, it is not controversial. The sourse I think is irrelevant unless you can show that it is inaccurate. The new papers aknowledge they can't account for changes seen over the first half of the Ordovician, that is stated in the text. You're correct the biodiversity plot is irrelevant but interesting. It made me think about a thing or two. I'm not really trying to refute the work. I'm just saying that these new papers have their own limitations just like the work that generated the previous estimate. In fact it seems a little remit of John that he clearly state the drawbacks of the previous study yet does not highlight them for this work. You can not say that the Young work now represents a new consensus on the subject. I'm not sure science works like that.
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  16. Galloping camel wrote: "Ten years ago the Hockey Team was supreme; anyone who dared to question their views was branded as stupid, venal or even evil. The "science was settled" was being trumpeted throughout the "Main Stream Media" and woe betide any brave soul who dared speak against AGW. You talk about "ad hominem" attacks but have you forgotten how dissenters were treated? If you need reminding, the Climategate emails may help. Take a look at the ones mentioning Patrick Michaels or Fred Singer. " I don't recall this series of events. As I recall, folks wanted to argue with Al Gore about whether warming was happening. In the context of whether CO2 causes warming (ie is a greenhouse gas, and is being released ed by humans) he said "the science is settled." 10 years later it still seems that ALGORE was correct. Can you point me to the emails that are melting the arctic or Greenland? Emails showing people being people do not change the science, nor most people's opinion of the science. Tom
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  17. gallopingcamel. I haven't read that article you linked but as far as I can tell it is not a peer reviewed article but made to look so. The lead author (http://www.sciencebits.com/ClimateDebate) also seems to be quite critical of the IPCC and realclimate anyway (maybe he has some "bias and prejudice"?). When independent science academys from different countries all endorse the core findings of the IPCC I will more likely believe the claims the authors make from these organizations than something else. In no way does it mean I accept what they say at face value (hence why i've joined this site.) Tom Dayton linked to this video in John's other post which I highly recommend. Naomi Oreskes addresses the whole idea of consensus in science. She finishes with a quote by Sir Bradford Hill made when he overcame his skepticism with the link of smoking and cancer: All scientific work is incomplete—whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time.
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  18. CBDunkerson at 02:26 AM on 13 March, 2010 "RSVP, your model for testing the existence of the greenhouse effect seems to be lacking a Sun. Put in a visible light laser being continuously fired at the anvil to heat it up and make sure that the energy flows are significant enough for instruments to detect and you'd have a valid comparison. " Sorry for not replying sooner. Not sure why a "sun" or continuous heat source is needed. When I refer to comparing a cooling profile, I am talking about tracking the cooling of the anvil over time, until the anvil reaches the ambiente (assuming it is well below 100 C or 150 C). You would then superimpose these curves, and for that small difference of CO2 in column of say 3 meters (pick your height), it is hard to imagine there would be any appreciable difference. The curves would lay exactly one on the other. This would essentially indicate to what extent CO2 affects cooling. (i.e., zilch). Just for grins, the experiment should be conducted for incremented percentages of CO2 all the way up to 100%. This might help confirm other theories such as what might be happening on Venus. Again. I am not denying that CO2 absorbs IR. What I am saying is that what matters is the relative heat capacities of say the anvil of our thought experiment and this ity, bity amount of CO2 gas. There are three ways matter interacts with light. At least I can only think of three. 1) reflects it (as in a mirror), 2) passes it through (as in clear glass), 3) absorbs it (as in a black body). If I was being told that GHG acted as a mirror, case 1, such that photon emission was being hampered from the getgo, I could understand this AGW theory. But the experts are telling me that CO2 ABSORBS energy (case 3), meaning that heat capacity is the determinant which implies CO2 is acting like a heat sink. And whereas the mass of a heat sink determines its efficiency, the extra 100 ppm of anthropogenic CO2 in our atmosphere is essentially zero as compared to the mass (an therefore heat capacity) of land, water, etc. 100ppm is even almost zero compared to the air itself. So if we are going to entertain disucussions of AGW, it might make more sense to look at the effects of slash and burn, farmlands, human structures such as buildings, asphalt on highways, warming of water in artificial damns, etc.
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  19. The fact that greenhouse gases absorb infrared radiation is rarely disputed - not even by Gerlich and Tscheuschner. But a body that absorbs, must necessarily also emit. This fact explains the division of the atmosphere into two layers: • at bottom of the troposphere where vertical circulation prevails and the temperature gradient is determined by the circulation and not by the radiation balance, and • above is the stratosphere , where the temperature profile is determined by the balance of radiation (absorbed energy of radiation = emitted energy of radiation). Boundary conditions for radiation intensities in the atmosphere are the high level of infrared radiation upward from the warm surface of the Earth, and the the practically non-existent downward infrared radiation from outer space. The total radiation from Earth into space must equal the absorbed radiation from the sun. Temporary fluctuations in this balance result in temperature changes which more or less (depending on the storage capacity of air, solid earth, ocean) quickly restore equilibrium. As a result of these conditions, the intensity upward flux decreases, and intensity downward flux increases. A temperature profile based on a dormant atmosphere which maintains the balance of radiation (absorbed radiation energy = emitted radiation energy, the vertical part would be reach to the surface) would show temperatures at lower altitudes changing quickly altitude increases (steep temperature gradient), such that initially small air movements increase rapidly - air that's a bit warmer than the surrounding air accelerates as it rises, and air that's a little colder than the surrounding air accelerates going down. The result is a temperature gradient that's nothing more than an edge case : When the air rising, the decrease in pressure causes it to cool at precisely the same rate as the surrounding air. Above, rising air would cool faster than the surrounding temperature decreases, causing it to drop back down to its resting point , leaving air stratification in a stable state. The driving mechanism of vertical circulation in the troposphere is that the air at the surface is warmed more than the surrounding air, and therefore rises. Because more is emitted than absorbed, the rising air is cooled, and gives off latent heat (from the condensation of water vapor) and the rate of ascent gets slower and slower until it reaches zero { this is the end of the troposphere. The convective and latent heat that is injected into the troposphere complements the energy balance at the surface. How quickly the pressure (or altitude) in the atmosphere is reached, at which the temperature is so high that the air stratification becomes unstable (the boundary between the troposphere and stratosphere - tropopause), depends on the absorption length of radiation in the atmosphere, as well as on the concentration of greenhouse gases. The higher the concentration, the faster the critical value is reached. Therefore, as a first approximation, it can be assumed that the column pressure of greenhouse gases in the tropopause is constant. But this is only a very rough approximation, since the temperature in the stratosphere has to decrease: As the surface temperature increases, wavelengths that the atmosphere only absorbs to a small extent, radiate for the most part directly into space. Consequently, the temperature conditions change such that less heat from the greenhouse gases radiates into space. This has the consequence that with increasing concentration of the greenhouse gas the column pressure decreases. Thus, the radiation conditions near the surface have practically no influence on the temperature profile. Arguments such as saturation of transparency through the atmosphere have no meaning. In the paper by Gerlich and Tscheuschner the tropopause is mentioned three times, two times that the tropopause would be mistaken with the ionosphere, and once in another quote. No connection to the greenhouse effect is shown - for Gerlich and Tscheuschner, there is apparently no cause for separation of the atmosphere. In reality, the actual location of the tropopause varies due to wind, etc. Note: At low pressures, there is still a temperature peak. This is the result of UV absorption and ozon e formation. UV is absorbed, but the absorbed energy is emitted as infrared. Since the UV is absorbed, the UV intensity decrease based on an e-function, and for small temperature changes, the emitted power is roughly proportional to the temperature. Based on this approach, the following equation describes the observed temperature profile between 220mbar (11 km height) and 1mbar (47 km height) very well. T = 56, 5°C + 67,3K * exp(p/5,03 mbar) The exponential term in this equation describes the heating (UV-ozone-process) from above. It follows that the heating from above can be ignored in case of pressures greater than 50mbar (< 20 km altitude: < 3 mK), and is not responsible for the constant temperature in the stratosphere. An increase in CO2 concentration leads to an increase and cooling of the tropopause. A water vapor feedback is not taken into account.
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  20. Chriscanaris @40: "I ask because people tend to resist making changes when not faced with immediate profits, costs, or like consequences. Moreover, we find it very difficult to consider consequences extending beyond our lifetimes (and perhaps our immediate offspring's')." I'm with you on that. The deacon's grace: Lord bless me and my wife, Son John and his wife, We four and no more. Science can often tell us, with a high degree of certainty, what will happen in the future. What it can't tell us is why we should care. It seems unlikely to me that Homo sapiens faces outright extinction. Population may crash, but there will be survivors, who will keep breeding. That's hardly an uplifting prospect, though. I'm glad I have no offspring.
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  21. RSVP, your 'scenario 3' is inherently flawed... CO2 and other GHGs do absorb infrared radiation (at various wavelengths), but they then re-emit it. Thus your argument that a 100 ppm increase in CO2 doesn't have the capacity to retain enough heat to cause significant warming is entirely irrelevant... NO ONE claims that is happening. Rather, because of that extra 100 ppm CO2 more infrared radiation which WAS going up and escaping out into space is instead absorbed and re-emitted back down... where it is then retained in things like the land and oceans which DO have the capacity to store a great deal of heat and cause global warming.
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  22. gallopingcamel at 11:53 AM on 15 March, 2010 In your reference Shaviv (I haven't seen this before?) was trying to respond to Royer around 5 years ago. It is hardly a direct rebuttal to the subsequent influential 2006 paper by Royer. Since then the evidence for CO2 (as a driver and amplifier) has continued to increase both in the paleo-record and in recent times, whilst very little convincing weight has been added to the evidence for the Cosmic Ray (Galactic or otherwise) hypothesis. As more work is done, and we look in more detail at the paleo records it is fair to say the scales are tipping further and many hitherto unresolved questions are finding answers (as in Young). This does not preclude other drivers (or most likely, combinations or drivers) of climate, but in the decades of intense research "CO2 as a significant factor throughout the history of the planet" has survived, and new corroborating evidence continues to emerge, plenty of it discussed here!
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  23. RSVP - CO2 absorbs then re-emits the energy, with fairly high efficiency. Some absorbed IR will (small percentage chances) be converted to molecular motion (hitting another air molecule at a high energy level prior to re-emission), a _very very__ small percentage will break molecular bonds (energy is low, but we're dealing in probabilities here), but the vast majority is incoherently re-emitted in a random direction as the electron shell of the CO2 molecule returns to its low energy state. I work with fluorescent dyes - this is fairly basic in molecular/photon interactions. This changes part of the IR vector from UP (hemispheric emission pattern from the ground to the sky) to spherically symmetric, sending some of it back down to the ground; the ground loses energy more slowly as a result. Even if it doesn't head straight back down, the IR now has a longer atmospheric path length, increasing the chances of hitting water vapor or other heating events in the atmosphere itself. CO2's not a mirror of IR, it's a randomizer. And ~50% (simplifying multiple absorption events, sums of series, etc.) of what gets randomized heads back down.
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  24. RSVP - here's a link I found for a fun animation of this. The animation only shows one direction of emission, unfortunately, rather than a spherical distribution, but it's still a useful illustration: CO2 and IR animation
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  25. My apologies, the first time I tried that and I put in a bad URL: CO2 and IR animation
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  26. John Cook says "CO2 is a strong driver of climate". This claim fails at all time scales. If this were true it would be easy to show correlation between CO2 concentration and global temperature. Modern times. There is good correlation between the variables from 1850 to 1998. Looking back from 1850 the correlation breaks down unless you re-write history by denying the Medieval and Roman Warm Periods. Looking forward, the variables have diverged over the last 12 years. Last 700,000 years. CO2 and temperature proxies correlate very well through several glaciations. However, CO2 frequently lags temperature by ~600 years. While correlation does not imply causation, it would be more plausible to suggest that temperature drives CO2 concentration than the opposite. Last 600 million years. See (#39) on this thread. Starting late in the Ordovician, Scotese et al. say there was a sharp drop in temperature followed by a rise. Hot, cold and then back to hot. Royer uses Berner's CO2 reconstruction which show fluctuations that are too small to account for these changes unless you torture the data by taking liberties with the large error bars.
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  27. For any readers of gallopingcamel's latest objection that CO2 does not correlate well with temperature, you should read CO2 is not the only driver of climate. I've given up on gallopingcamel him/herself.
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  28. KR and CBDunkerson I am quite aware of this idea that each little CO2 molecule acts as an isotropic IR radiator, creating a situation not unlike how bumpers and flippers in a pinball machine delay the ball on its path downward, however, you cant get something for nothing, and the only extra energy that will hang around, will be that associated with an increase in the net heat capacity of the atmosphere, which is a direct function of the mass and heat capacity of the extra gas in question. So I am acknowledging that anthropogenic CO2 should affect an increase in temperature of the atmosphere, however, it can't do this any more than what is associated with its inherent heat capacity, and as I said above, 100 ppm doesnt seem like much to me. And as such, I think this is different from acknowledging AGW, which basically attributes glaciers receding and notable worldwide average temperature increases to the extra CO2.
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  29. RSVP - I actually consider the CO2 reflection of IR back to the ground _considerably_ more important than mass heating of the atmosphere. Very little of that IR goes into molecular heating of gases; CO2 is an efficient radiator. It does, however, reduce radiation losses from the ground, and change the steady state temperature conditions of the surface - in order for the steady state thermal conditions to stabilize with a lower percentage IR loss to space, the ground warms up and emits more IR. Hence global warming. More of the atmospheric heating comes from convection/conduction and evaporative heat transfer than from direct IR. And increasing GH gasses directly reduce the percentage of IR loss. See this lovely graphic, which appeared in the course of the "Is CO2 a pollutant" discussion: http://www.windows.ucar.edu/earth/Atmosphere/images/earth_rad_budget_kiehl_trenberth_1997_big.gif This shows an excellent overview of the steady state thermal condition. It's not the heat capacity of the atmosphere at all, but the rate of energy flow in and out of the ground/atmosphere system. Even with a _zero_ heat capacity of the ground and water (for a thought experiment), the greenhouse gas energy flow rates would set the steady state condition - the heat capacities act as inertial buffers on the steady state condition and on dynamic events (clouds, storms, El Nina, insolation, etc.)
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  30. KR 1+1-1=1. Do you agree? If so, we agree on something important. Next step. Heat (1) that would otherwise radiate into space is impeded (so you say) by the CO2 (i.e., never leaves, or is returned which is equivalent). Now, this either elevates the surface temperature, or it elevates the atmosphere's temperature. Which is it? It cant be both. If you don't agree, please let me know how this unit of energy heats both atmosphere and surface simultaneously. Thanks in advance.
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  31. KR And there does seem to be something strange about the lovely graphic. 1) 342 incoming, somehow becomes 390 outgoing. That doesnt even makes sense at noon. But if you were considering a 24 hr average, it makes even less sense. 2) The graphic shows 342 incoming. Nice Sun shine, I can relate. But then it shows 324 back radiation. That isnt far from 342. I should be feeling a nice warm glow as I step outside at night, but this is not my experience. Out till which hour in the evening does this last? Thanks in advance.
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  32. RSVP - if you read the entire graphic, the surface exchanges are +168 insolation, +324 back radiation (reflected to the surface), total of 492 w/m^2. The outgoing is 24 convection, 78 transpiration, 390 IR, total of 492 w/m^2. 492 = 492, dividing by 492 leaves 1=1; the equations are balanced. As to nightfall, I believe this is a daily average, adjusting for Earth surface area and angle of solar incidence. Regarding atmospheric temperature; part of the atmospheric temperature is due to direct insolation (67 in this diagram), and a larger part is due to ground IR (390-40-324=26 absorbed), convection (24), and evaporative heat transfer (78). Meanwhile that 324 w/m^2 reflected by the atmosphere - it is reflected to the ground, warming it, increasing ground temperatures and then indirectly warming the atmosphere through the aforementioned pathways. GH gasses act as insulation. They slow heat loss from the Earth; more insulation/lower loss causes an accumulation of more solar energy, leading to a warmer Earth, radiating more energy at the surface. That balances out the steady state condition at 1=1, solar input to radiative output. If the back radiation went from 324 to (say) 325 w/m^2 due to higher CO2 (atmospheric outgoing changing from 235 to 234), the extra 1 w/m^2 energy imbalance will heat the surface until thermals/evaporation/radiation increased to match it. I think that's pretty straightforward. As to that warm glow - I think the estimate is we're ~33 degrees Centigrade warmer than we would be without GHG heating. That would be a noticeably colder night...
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  33. Sorry, the ~33 degrees C is an average over the day. Looking at lunar surface temps (higher than the Earths would be, as the moon has a lower albedo), night temperatures without the atmosphere would be about -153 C. Wear warm socks...
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  34. Peter Hogarth (#72), the Royer/Shaviv thing has been going on for some time. Royer's latest update (2010) will likely evoke some response from Shaviv. While I don't buy Royer's exaggerated claims for the role of CO2, I am skeptical about Shaviv too. Shaviv has suggested that the Earth's position relative to our galaxy's spiral arms can affect our climate. Sounds like weird science but remember that Plate Tectonics was laughed at for many years. You appear to be keeping an open mind with regard to climate drivers other than CO2 or cosmic rays. That makes perfect sense to me; it already seems pretty obvious that the GCMs are way too simplistic.
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  35. RSVP (#68 & #78), I am reluctant to disagree with someone who appears to be on my side considering that we are out numbered and out gunned on this blog. However, the limited heat capacity of CO2 (given the very low concentration in our atmosphere) can be ignored as any energy absorbed by a CO2 molecule is rapidly shared with other gas molecules in the atmosphere.
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  36. #84 gallopingcamel at 06:53 AM on 17 March, 2010 "seems pretty obvious that the GCMs are way too simplistic" It's not obvious at all, quite the contrary. I would say they are overcomplicated structures on rather shaky physical foundations. Terrestrial climate is a heat engine based on water as a working fluid. Common sense tells that much, one does not even have to be a climate scientist to know that much. Weather-talk is about precipitation or the lack of it, what else? And exactly the water cycle is the most poorly understood part of any computational model of climate. Need to say more?
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  37. Whoa! There needs to be a geologic timeout here. Way back at 50, Peter Hogarth mentioned "None of this work precludes other drivers (lesser or greater) for global temperature and climate, and in geological history as well as now, other factors must be taken into account (such as insolation, plate tectonics, etc)" It is vastly out of context to make any comparisons between the present and the distant geologic past without plate tectonics. The globe looked very different 450 million years ago: no land mass at the North Pole and a super-continent at the South Pole. That paleo-geography is a major control on oceanic circulation and thus on climate is well-established among geologists. See this discussion of the Ordovician of eastern North America for an example. Some of the best evidence for Ordovician glaciation is in the present day Sahara and in South America; these areas were near the South Pole at the time. See also this summary article on the Ordovician climate, concluding thus: "It therefore seems likely that it was geographical factors, rather than the chemical composition of the air, which played a key role in triggering that glacial period."
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  38. Hello, i think i stumbled across an "Undead" thread here.

    I googled for "co2 levels ordovician" and was linked here, after reading i registered and commented. After a few hours my probably flawed post was deleted. If i type "ordovician" in the SkepticalScience search bar i get 2 related links, exlcuding this thread. I guess it is obsolete, since the ppm values of Seth Young (2009) are considered wrong (5000) ppm.

     

    What kind of makes me sad is that the 2 pages of comments in this "undead" thread will get lost as contemporary witnesses (?). It is interesting to see how the debate was 9 years ago. Aint it possible to merge these threads and maybe make a notification that, at this point people had obsolete data?

    Thank you for your patience.

    Oh one more thing: The linked tool "tinypick,com" to HTML post graphs is obsolete, it now links to "Photoshop" now which is not free.

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    Moderator Response:

    [PS] All threads are live. Most users follow the site with the "comments" menu item which show activity everwhere. However, your comment was deleted because it was a gish gallop and unsupported by appropriate references. Please ensure your comments conform to our comments policy.

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