Study: Ice age thermostat prevented extreme climate cooling

From the UNIVERSITAT AUTONOMA DE BARCELONA and the “department of settled science” comes another global climate thermostat story. Just last week, we were told the Earth had no thermostat. Gotta love it when climate science is so robustly definite, eh?

Ice age thermostat prevented extreme climate cooling

During the ice ages, an unidentified regulatory mechanism prevented atmospheric CO2 concentrations from falling below a level that could have led to runaway cooling, reports a study conducted by researchers of the ICTA-UAB published online in Nature Geoscience this week.

Atmospheric CO2 concentrations swung over a range of 100 ppm (parts per million, by volume) during the ice ages. The exact processes behind this variation have been difficult to pinpoint, but it is known that changes in the storage of carbon by photosynthetic organisms played an important role.

“When we took a close look at measurements from ice cores, we noticed that atmospheric CO2 concentrations hovered close to 190 ppm during much of the past 800,000 years, but very rarely fell any lower,” said Sarah Eggleston, a researcher at the Institut of Environmental Science and Technology (ICTA-UAB) and co-author of the study. “This was surprising, because it suggests that these very low CO2 concentrations were quite stable. What’s more, we know that CO2 was often very high in the distant geological past, but we have no evidence that CO2 concentrations were ever lower than 190 ppm.”

“We know that, over hundreds of thousands of years, CO2 is regulated by slowly reacting with exposed rocks” explained Eric Galbraith, lead author of the study and an ICREA professor at ICTA-UAB. “But this would be too slow to explain the stability during periods of only a few thousand years, as we see in the ice cores. So it must have been some other mechanism that kicked in at very low CO2.”

The authors suggest that it was most likely the biosphere that maintained habitable temperatures, since at very low CO2 levels, plants and phytoplankton struggle to photosynthesize. Slower growth of these organisms would have meant less carbon in the soils and deep ocean leaving more in the atmosphere, and preventing CO2 concentrations from falling further. This might have prevented extreme cooling that would have led to Earth freezing over as a ‘snowball’.

However, the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.

###

A lower limit to atmospheric CO2 concentrations over the past 800,000 years

Global temperatures and atmospheric CO2 concentrations varied widely over the glacial cycles of the past 800,000 years. But despite this variability, Antarctic ice cores have shown that CO2concentrations were very similar during all the coldest points of these cycles. Remarkably, the recurring minimum CO2 concentrations (190 ± 7ppm) fall on the lower bound of any known in Earth history. Here we show that although the volume of terrestrial ice sheets was normally distributed over the past 800,000 years, as might be expected from the approximately normal distribution of the orbital forcing that drove the glacial cycles, Antarctic temperatures have a strong cold mode, whereas CO2 concentrations have both a cold mode and a central mode. Although multiple explanations are possible, the recurring CO2 minima and pronounced cold modes are consistent with a strong negative feedback to decreasing CO2 that resisted further cooling on timescales shorter than 10,000 years. We suggest that one possible negative feedback is CO2-limitation of photosynthesis, either directly or via CO2-limitation of N2 fixation, which could have inhibited further lowering of CO2 by reducing carbon storage.

Full paper: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2914.html (paywalled)

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112 thoughts on “Study: Ice age thermostat prevented extreme climate cooling

  1. The smartest thing ever invented is the thermos flask.

    It keeps the hot food hot; and it keeps the cold food cold.

    How the hell does it know ??

    Everybody enrolling in a climate change class, should be given their own personal thermos flask.

    G

    • Most natural processes have damping feedbacks, or the whole system would go into a runaway. That’s why the logistics curve keeps popping up in nature. Hint: global warming probably has its own negative feedback too.

      • It’s NOT feedback !

        Simply le Chatalier’s Principle.

        All physical systems adapt to neutralize any external disturbance.

        Physical systems are in a state that is dictated by all of the variables. If ANY of those variables change for whatever reason, the stable state shifts to the NEW stable state prescribed by that set of variables.

        What’s not to understand ??

        IT’S NOT FEEDBACK

        G

      • “All physical systems adapt to neutralize any external disturbance.”

        A disturbance produces a gradient that increases the potential energy of the system. Systems trend to the lowest potential energy. Entropy should probably join gravity, electromagnetism, and the strong and weak nuclear forces in our pantheon of forces of nature.

  2. Although multiple explanations are possible

    Archived in the drawer of nice conjectures without supporting evidence.

    Why do these articles so rich in speculation and so poor in evidence keep being published?

    • I humbly submit it is called a hypothesis. Newly discovered facts, here, are thrown at the wall and the game is on.I’m not a scientist so you can throw my hypothesis out with all the contempt you can muster if you so choose.

      • Actually it is not even a hypothesis. A hypothesis has a lot of work behind and explains most but not all the evidence available (example the CO2 hypothesis of global warming). A theory is when it explains almost all the evidence even from related disciplines (example the theory of evolution). When an idea just explains a little bit of evidence and has little work behind we like to call it just a conjecture. The idea that biological systems prevent CO2 levels from falling below 190 ppm is just a conjecture. Conjectures are just where scientific work starts, not where it ends, and are rarely deserving a publication unless they come dressed with interesting experiments or new evidence that increases our knowledge.

        The article presented is undeserving of all this attention. Good for them that they placed it in a nice journal, but it is not a good article.

    • I thought you guys were lamenting the total lack of research into anything except anthropogenic CO2. They should look at natural climate change is the cry. Yet whenever someone publishes a study about natural climate change you slag it off.

      • In another place you said:

        These authors say that if CO2 levels did not fall below 190ppm “strong negative feedback to decreasing CO2 that resisted further cooling on timescales shorter than 10,000 years.”

        So, clearly, you and they think CO2 is the temperature control knob. The majority of us here disagree. We are being completely consistent. It doesn’t matter if it is anthropogenic or natural, CO2 is not the temperature control knob.

      • So are you suggesting that climatologists ignore CO2 they should reject this from any consideration, even when applied to periods before human generated CO2? If they include natural CO2, the research is illegitimate because… what?

        I must say this a novel approach to science.

      • We had enough for a day with the study that says that up to 50% of sea ice loss is natural. Big hit to Arctic alarmists. Now they have to go an protest to Gaia.

      • seaice1 March 14, 2017 at 3:52 pm

        So are you suggesting that climatologists ignore CO2 they should reject this from any consideration, …

        The premise that CO2 controls the planet’s temperature is wrong and this invalidates their conclusion. It’s simple logic.

      • It would be logic if your premise was correct, but since it is not it is just wrong. Do you say that CO2 cannot cause warming through the so-called greenhouse effect? It is good to know because either you think that is the case, or you must logically agree that CO2 must be included in considerations of past climate.

      • seaice1 March 15, 2017 at 12:35 am

        CO2 may have some effect on temperature. It is clearly not the main thing that controls global temperature, which is what the article assumes. The paper clearly says that the global temperature didn’t drop further because CO2 didn’t drop below 190 ppm.

      • Seaice says “I thought you guys…”

        There is no “you guys” although most here probably are actually guys, not that it means anything in the modern world.

  3. The ice ages of the past ~3.2 My are certainly an anomaly in Earth’s geological history of the past 600 My.

    And it came damn close to biosphere death, To Wit:
    “Remarkably, the recurring minimum CO2 concentrations (190  ±  7 ppm) fall on the lower bound of any known in Earth history. ”

    The clueless climatist bedwetters think that even 285 ppm CO2 is ideal, merely for a political agenda that has at its core UN Agenda 21 and global socialism. Just today, Gavin Schmidt dishonestly posted on his Twitter feed his beyond idiotic “belief” that 100% of the Earth’s warming since 1950 is anthropogenic. I’d agree only to the point that the has been no real warming since 1940-45, and the warming 1950 is merely mand-made synthetic manipulations of data.

    If the Earth gets to 650-700 ppm by the end of the easy fossil fuel era (~100 to 200 yr from present) , we will likely have a climate and biosphere optimum. And we’d better have fossil fuel’s nuclear (fission and/or fusion or even exotic single point energy) power replacement in place globally. The clock is ticking.

  4. The oceans hold huge amounts of CO2. I would think they would be a better regulator than plants.

    Even during ice ages, a large part of the oceans remain ice free.

  5. This might have prevented extreme cooling that would have led to Earth freezing over as a ‘snowball’….

    ………”the positive feedback loop takes over and the runaway snowball effect is pretty much unstoppable”

    8-/

  6. CO2 has negligible effect on temperature after the first 100 ppm. Most plants however need a higher level than that to grow healthily and reproduce.

    • Wonderful story. I just cannot read Nat Geo because of their stand on climate change. Here is an ironic quote from this article: “And because scientists are first and foremost human beings, they’re loathe to change their theories or their minds because of mere data.”

      Mere data.

      • Besides my having grown up at the eastern edge of the scablands, and having driven countless time through them while crossing the state, I appreciated the lack of CAGW reference, and the irony of the tribal mentality so frankly described. Read the comments, there are some poignant ones.

    • Everybody, especially from the science settled bunch, should see the scabland floods all the way from the lake bed in Missoula to the mouth of the Columbia. I did after a friend took an amazing geology field trip there. I have a rock from a gravel bar in Moses Coulee the size of a cantaloupe and pictures of the huge, by usual standards, ripple marks. Don’t mess with water.

  7. Earth has a thermostat. Sort of. Only it doesn’t work the way these “scientists” think it does. CO2 isn’t even one of the knobs, just along for the ride pretty much. It’s a crazy quilt kind of thermostat, which we’ve only started to get a handle on.

    • We are not permanently frozen and the Oceans are not boiling, so something is keeping it within limits. If we call it a thermostat it might not be completely accurate, but it is a term everyone understands.

      • For some reason, some people think that ALL feedback systems contain an amplifier that has a forward gain of one million.

        Ergo, with negative feedback they control the variable to a gnat’s eyebrow.

        If climate systems contain any net gain amplifiers at all, they certainly aren’t any more than one digit gains.

        Nobody ever pays any attention to the phase shift in feedback systems. A great many real feedback systems operate with at least a 90 degree lagging phase shift.

        We should stop talking about climate as if it was a feedback circuit. It’s just things following the laws of physics wherever they wander.

        G

      • Compared to stability at minus 50 degrees C during a Snowball Earth to 50 degrees C above zero coming out of one, yeah.

  8. “When we took a close look at measurements from ice cores, we noticed that atmospheric CO2 concentrations hovered close to 190 ppm during much of the past 800,000 years, but very rarely fell any lower,” said Sarah Eggleston, a researcher at the Institut of Environmental Science and Technology (ICTA-UAB) and co-author of the study. “This was surprising, because it suggests that these very low CO2 concentrations were quite stable.
    ————

    They have took a close look at the measurements from ice cores…….really hilarious……..wondering how good their minds are to make any sense out of the ice core measurements……gosh.

    There from the very start, lying out of their teeth……

    cheers

  9. Does anybody have a chart of the correlation of CO2 with temperature as a function of interval from past to present ? Ie : over the last 1K , 1M , 10M .. intervals ? Is it significant for any of those intervals ?

  10. “…suggesting that the Earth does not have a similar mechanism to prevent rapid warming.”

    It doesn’t suggest such a thing. This unscientific phrase undoes whatever good this paper might have. In simple minds, because they suggest a lower limit to the level CO2 will reach because of limited photosynthesis, they assume that photosynthesis is the only mechanism for removing CO2 from the atmosphere and therefore unbounded heating can take place with increases in CO2. I take issue, as most would, with their first simple idea that this limits how cold it can get. CO2 isn’t the only actor in temperature – the control knob CO2 idea has been torpedoed incessantly over the past couple of decades as well as shown in paleo data. A large volcanic explosion would put aerosols in the atmosphere and undersea ones could warm the ocean particularly in the Pacific Ring of Fire , a huge earth quake and Tsunami would break up ice and allow direct insolation, the sun can vary, geothermal heat is always heating from below and even under antarctic and arctic ice caps water is liquid from this – there is a lake with life in it beneath several km of ice in Antarctica. Indeed, the sun itself has a limiting factor on how cold it can get – why do you think planets get colder the farther out you get. How about Titan with methane seas and atmosphere – a gas that is according to legend a thousand times more powerful a greenhouse gas than CO2 ………………

    • Gary – completely agree about the un-science.

      There is a low limit mechanism; there is an upper one that no matter how high the CO2 goes, 7000 ppm, the temperature is limited to 24 C. When that happens, the Arctic becomes habitable and farmable. Greenland will melt, Hudson Bay will expand into Canada, vast farmlands will become fruitful once again.

      It will also start raining again in the Sahara and the vast Gobi Desert. Sahelian Africa will become the breadbasket of the world.

      I am OK with that.

      • Crispin,

        my belief for years. Whilst the Green Goblins bang on about an imaginary desertification of……well, errrr….desert regions, they utterly ignore the land released for farming in the NH.

        And whilst, under those circumstances sea levels would likely rise, it would be over hundreds/thousands of years.

        But the Green Goons are actually only worried about their own, coastal real estate. Oh how they would suffer, having to lose their precious houses and be forced to move inland, onto a newly defined coast, over hundreds/thousands of years.

        But of course the problem is immediate and catastrophic.

        Lobbox!

    • The Methane GHG is obviously why Titan is so warm…
      Actually
      Titan’s surface temp is -290F or -179C
      Enceladus’ surface temp is -330F or -201C
      Mimas’ surface temp is also -328F or -200C
      So the GHG Methane (And atmospheric pressure) RaiseTitan’s temp by 40F or 21C

    • “However, the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.”

      Gary, I agree this is on the face of it senseless. Not revealing something does not suggest it is not there unless it would very likely have been revealed by whatever process we are talking about. So if I look into a top hat and don’t see a rabbit it does suggest that there is no rabbit there. If I don’t see a rabbit in a field it does not suggest there are no rabbits in the area.

      This leaves us, as far as I can see, with several possibilities.
      Either the author of the press release has totally overstepped the mark and reported stuff the paper never concluded.
      Or the paper totally overstepped the mark and reported stuff that it could not reasonably conclude.
      Or the paper explains why it would have found such a mechanism if there were one, but the press release did not explain that to us.

      My money is on the first one, so I don’t think we can conclude that the paper is faulty without reading the whole thing.

      This sort of stuff from press releases is all too common, they are becoming more like sensationalist newspapers. There seems to be a great temptation to put stuff in the press release that the authors would not dare claim in the paper. This should be resisted, or at the very lest it should be made clear that these statements are not conclusions from the paper, but speculations based on them.

      • Now this is a reasonable observation on the condition of, not only this press release, but most of the MSM. Half read, badly understood scientific papers, reported to the public, by journalists desperate for their next sensationalist headline, to sell newsprint. Or in this case, to attract attention to a scientific paper that is probably no reflection of a promotional press release.

        Now whilst the alarmist community maintain 97% consensus amongst scientists, we all know full well there are tens of thousands of scientists out there that utterly refute that CO2 is the control knob for the earth’s temperature. But for sensationalist reasons, the MSM et al continue to trot out the false 97% statement.

        By your own admission Seaice, you recognise the reporting of a paper in a PR stunt to be dubious at best. Yet you continue to maintain that CAGW is real, despite the very real evidence to the contrary.

        Why can’t you go the whole hog and concede that most climate change reporting in the MSM is rubbish and the foundation for that rubbish is weak, distorted science?

    • and then there is the tilt of the earth and the orbit around the sun. When these, along with the suns out put compliment each other, in the positive or the negative, you could easily effect climate (temperatures)

    • This claim is particularly idiotic when one considers that the world has heated up, then cooled down, then heated up, then cooled down….multiple times. Implying that the temperature cannot go back down at some point is as stupid as claiming that the temperature cannot ever go back up. Did they even look for an opposite feedback? In that vein, if there is not a similar mechanism, how have CO2 levels dropped in the past? Something must have caused it….multiple times.

  11. Using a proxy record (ice cores) that has been demonstrated convincingly to show that CO2 levels FOLLOW temperature trends with a lag of about 800 years, they were able to conclude that CO2 levels were somehow controlling how cold it can get?

  12. Holocene ice core records consistently exemplifies that atmospheric CO2 concentrations follow temperature, not the other way around. So the authors premise that a CO2 floor of 190 ppm is a thermostat limit, does not make sense. As Patrick Moore has stated on this website, Photosynthesis shuts down at about 180 ppm, That could well explain the CO2 bottom limit, but it has little to do with temperature modulation.

      • Of course, the real problem with low CO2 is that as CO2 levels are reduced, plant reproductive mass is the first to be affected, and it is the reproductive mass, i.e. seeds, which we use as food (we eat wheat grains, not wheat stalks).

        e.g. https://link.springer.com/article/10.1007/BF00328894

        Most food crops are C3, and their food yield at 180 ppm is so low that if we ever reached this level again, the world could not possibly support a population of several billion, as it comfortably does at 400 ppm. I don’t have much data for C4 and CAM food crop yields at low CO2 levels, but I suspect their yields suffer just as much.

        The organization calling itself 350.org, which wants to reduce CO2 levels to 350 ppm, is actually advocating genocide on a level beyond Hitler’s wildest dreams. The last time CO2 levels were at 350.org was in 1988, when the world’s population was a tad over 5 billion. We now have over 7 billion. If by some magic means we could reduce CO2 levels back to 350 ppm, the resulting reduction in crop yields would likely produce mass starvation in some parts of the world.

      • Aside from NOAA s calculation that half of the anthropogenic co2 is being sunk in the oceans and land, the difference between what should be in the atmosphere and what is unaccounted for in one recent year was 7 billion metric tons. Let me note that this is not a variation, each and every year is missing co2. Of course I think some of the uptake is related to increased plant growth , but not all. So that leaves us with a couple of different scenarios. One of which, is the amount of natural co2 declining ? If so, and what is/are the source/s. Being that early on they were telling us that they could tell the difference between natural and anthropogenic co2 by the isotopic ratios. They haven’t stood by that statement in awhile, because I don’t believe they can. Along with the other statement about how long co2 stays in the atmosphere, hundreds of years, according to them. At the current rate of sinking, if we stopped all anthropogenic co2 production today, in 40 to 60 years, we would have catastrophic collapse of plant life. Just for reference the sink today is 1 1/2 times bigger than all of the co2 produced in 1965. And a little over 2 times adding in the missing co2 that isn’t accounted for in the oceans and land, and not accounted for in the increase in atmospheric co2.
        I don’t know what the actual ratio of natural to anthropogenic co2 is. I don’t know whether or how much of the rise in total co2 is attributed to anthropogenic co2. And why are the sinks expanding so much ? The earth didn’t increase in size. There has to be a reason. If anything, the sinks should be smaller now than 1965.
        I can point to temperature graphs that show we were at the height of a warm trend 800 years ago, that’s before the IPCC and friends flattened it.. just made it go away. (what MWP ? ) and since the the ice cores show that co2 lags temperature by 800 years, is the increase solely been by the lag ? Or the underlying warming trend of the last 150 years ? There are no negative numbers in the co2 record for the last 150 years, unless NOAA has decided to adjust that, which indicates to me that the steady rise in co2 is some relation between natural warming and the 800 year lag. The warming in the record 950 years ago started at the same time co2 levels started increasing, slowly, 150 years ago. Co2 rate of increase ppm year has paused, they paused almost 20 years ago. It has been around 3 ppm per year for that long.

      • According to the CAGW alarmist contention, having plants to survive on during low levels of atmospheric CO2 would be the least of our worries as we would have frozen to death long before starving.

  13. Three articles down is a paper explaining why/ how snowball earth did in fact occur. So on one random wuwt front page two research teams flatly contradict each other, whilst yet managing not to cross-refer. Funny old world innit?

    • Mr Julian. they do not contradict each other. These authors say that if CO2 levels did not fall below 190ppm “strong negative feedback to decreasing CO2 that resisted further cooling on timescales shorter than 10,000 years.” At the very start we are told this is about the last 800,000 years.

      The snowball earth in the last article was 600-700 million years ago. There is no contradiction at all.

  14. If the authors wanted to speculate on the subject of atmospheric levels not dropping much lower than 190 ppm, the likely speculations would have been…was the ocean saturated?…did ice cover block further CO2 absorption?…were volcanoes continuously spewing CO2?…etc

    The least likely areas to speculate upon are …was plant life starved off to the point plants no longer absorbed CO2 from the atmosphere?…. did the world cease cooling off because CO2 levels ceased dropping?

    SR

    • Also CH4 is transformed into CO2 not long after emission. The crust is constantly emitting CH4. That means there is a continuous supply of CO2 with a delay of a few years. It may be entirely responsible for the 190 ppm minimum and there is no ‘lower limit’ at all, absent natural gas seeps.

    • Puny is right. C3 plants don’t usually die at 150 ppm, but they surely don’t thrive. Optimum for them is up to 1300 ppm. This group includes the vast majority of plant species, ie all trees and many of the most important food and fiber crops.

      The CAM and C4 plants get along OK at much lower levels than 100 ppm.

  15. Obviously the authors aren’t acquainted with the ocean/atmosphere interaction–it’s all very simple if you look at the oxygen isotope/CO2 curves. CO2 always lags atm temp–i.e., the temperature of the oceans are the limiting factor

      • By about 800 years, which matchs the thermohaline circulation period. Makes perfect sense.
        _________________________________

        Thermohaline circulation is not a conveyor band going into maintainance mode after a full cycle.

        Just goes on and on and. ..

  16. Any ice core guys on this thread?

    I have read that the ice cores are very misleading on both end of the bell curve. That is, they miss the big peaks and valleys in the data because of diffusion of gas in the snow as it is being compacted into ice.

    Is this accepted? And, if so, how would that impact this sort of paper?

    • Not an ice core guy, but read hundreds of papers for my last two ebooks. See Cause and Effect for a sampler. There are two issues. On short time frames (~60 years until firn turns to solid ice, there is atmospheric diffusion that introduces short term uncertainty. One ice, diffusion slows greatly, but deformation sets in introduing long term uncertainty. From what I have read, stuffmover 60 years in resolution with an ice core showing little annual deformation should be quite reliable. Themolder the ice (hundreds of thousands of years, like Vostok) the more deformation injects uncertainty. So there is a nice ‘fairly certain window’ of a couple of glaciations.

      • ristvan
        March 14, 2017 at 1:28 pm

        ristvan
        According to the info in this article…….these “guys” seem to have get to all their siency thing by taking a close look at the ice core measurements…the measurements….directly at the “raw data”..
        Can’t you spot the problem, or am I imagining one that does not exist!?

        cheers

      • ristvan @ 1:28

        So from your reading do you have a feel on what the actual error bars might be on say 350-450k old CO2 levels from ice cores?

        It seems to me that this is not discussed much but is surely quite important in deciding just how unusual the present 400ppm is.

    • Same issue with ice core temperatures Joel – resolution. You just may not see the exact peak and low-level of temperatures averaged out during the ice core interval. Resolution is lost. It leads to the misconception that all the extremes are recent.

  17. They should have looked for methane. When the plants die they decompose and produce methane, which as all know is a very potent GHG. Case solved, send the money immidiately.

    • SF, true but. Most methane clathrate is biogenic from sea floor methanogens. But the reason there isn’t more is methanotrophs. The marvelous world of Archea organisms. Regards.

  18. Of course there was a thermostat and there was not a thermostat. That is in the past. Climate science cannot tell us anything about the past. Not even what a thermometer measured 20 years ago.

    All that has nothing to do with the future.
    Climate Science has absolute faith in the future. The Science is Settled.

  19. Does anyone find it odd that in this most ‘settled ‘ of sciences that the ‘heads you lose , tails I win ‘ approach is seen so often ?

    • Nobody said this was the most settled of sciences. Gravity, mechanics, evolution, thermodynamics are all much more settled. The claim is that certain aspects, such as that CO2 is a greenhouse gas and warms the planet are settled.

      • What about Water Vapour…you know the ‘greenhouse gas’ that ‘cools the planet’…?

      • “The claim is that certain aspects, such as that CO2 is a greenhouse gas and warms the planet are settled.”

        Yet there is no empirical evidence, in the real world (not test tubes) that human generated CO2 causes GW. Far less that it would be catastrophic. Indeed NASA tells us that increased atmospheric CO2, man made or otherwise, has caused the planet to green by 14% over the last 30 years.

        Is there any negative result of increased atmospheric CO2 that can compete with one single 14% benefit from it? I would contend not. Indeed, I would go as far as to say that the combination of all the supposed negative effects of increased wouldn’t stack up to 14%.

        But instead of the benefits of ‘Greening’ being celebrated by the ‘Greens’ it is ignored.

        It does make one wonder what the true motives of the Greens are.

  20. It meets the ‘reasonableness test’ to explain a low limit of CO2 because of plant growth. Plants get all their carbon from CO2. With low CO2 there is little to ‘consume’ and therefore less is deposited or sequestered and taken out of the system. As less and less is sequestered, there is less to decompose back to CO2. As a result a lower limit is approached.

  21. One of the most profound undergrad chemistry lectures I can remember all those years ago was about equilibrium reactions. Its amazing how many times that concept has come up in later life.

    When a system is in equilibrium, the chemical/physical reactions move in a direction to offset the effect of an external influence. These equilibrium reactions, in balance, can stop the system running away to extremes.

    For the earth sea-atmosphere system one has to think that the various liquid-gas reactions in equilibrium have two extreme endmembers: an interglacial earth, and a glacial earth. Probably thats as far as the climate goes in each direction, although in geological history it is suspected that the whole earth has been glaciated.

    Its tempting to think that the external influence (variations in the sun insolation plus orbital variations) drives the equilibrium to variations in water evaporation, cloud formation and rainfall, leading to surface climate variation.

    • The northern hemisphere (NH) goes into glaciation when NH glaciation falls very low because of orbital (Milankovitch) cycles. During these times the southern hemisphere receives a corresponding increase in insolation. It is the Earth’s response to lower NH insolation that produces the glaciation — factors like increased ice, land, and possibly cloud albedo. For a given geography characteristic, there is a limit as to how far Earth can drive glaciation and thus temperature and thus CO2.

  22. The idea that CO2 below 100ppm would cause runaway cooling is just as bogus as claims of runaway warming, the models of both presume 1) CO2 drives temperature and 2) there’s an infinite source of Joules to power the gain (per the Bode model). Consider an electronic amplifier (the model used) with the signal input and the power supply input connected together (the bogus presumption that the assumed, infinite source of Joules is the Sun). Will you ever get more power out of the amplifier than is going in to the power supply input?

    The idea that biology keeps CO2 levels from dropping below about 100 ppm is absolutely correct since biomass is still thriving in tropical regions, moreover; biology also contributes to why CO2 lags temperature. It takes a while for biomass to populate and maximally utilize land whose ice covering has melted away. Going the other way, it takes a while for snow to accumulate deep enough to kill off alpine and other cold tolerant forests.

    • Co2 levels below 100 ppm and nothing is thriving. What’s left is puny, and probably a lot has disappeared. We never, ever, ever want to see levels at 100 ppm. In fact, I like the current levels at 400 ppm. I’m not really a fan of them going back to 280 ppm.
      If co2 lags temperature by 800 years, or so the evidence from ice cores, then what was happening 800 years ago ? We do know, we talk about it all the time. Mostly, we are all talking about a pause in temperature over the latest 18 to 20 years. In spite of continued upward production of co2, co2 increases per year have paused. Since we are at the top of the temperature range 800 years ago, during a warm period, it will be interesting to see how much of an influence anthropogenic co2 has on co2 levels. I am firmly convinced co2 follows temperature, and is still following temperature. The question for me is, why 800 years ? I have other questions as well.

      • rishac,
        Vostok has the delay at about 800 years, but the temporal positioning is troublesome and the delay varies over a wide range. The DomeC cores have much higher resolution and much better alignment. The delay is a more consistent with arboreal biology and between 100-200 years, with a slight asymmetry between rising and falling.

        You are right that below 100 ppm, biology basically stops and for the sake of agriculture, I would like to see higher CO2 levels than we currently observe. However; the proper causality is that biology stops and then CO2 drops below 100 ppm and this is INDEPENDENT of temperature. Biology will continue in the tropics, but the tropics are a smaller fraction of the biomass when the rest of the planet is covered in ice, hence the lower global concentration. I will bet that locally during ice ages (i.e. in the tropics), CO2 concentrations are even higher than the ice cores suggest.

      • Whatever else might be, not disagreeing, I’m working with what has been put out there. Clearly, when the inconvenient truth was put out there, they conveniently left off that in their own research co2 lagged temperature by 800 years. Whatever their reasoning was, not to include that destroys AGW.

      • There is something else that affects co2 levels. It’s cosmic rays. Also, in the presence of strong sunlight co2 breaks down into o2 and carbon, directly. There are no percentage numbers on that. Then they would have to address a stronger or weaker sun. I can’t wait for TSI to come up again.
        At 400 ppm a 1 % in increase in conversion would take 4 ppm out of the equation if the current is zero. I had the thought that the carbon black they are finding in the Arctic may be from that process. It’s raining carbon. And the process could be subject to any number a quirks. There also could be, under current conditions, an upper limit on the co2 total.
        1) we could be just seeing co2 increase simply because of what happened 800 years ago.
        2) the sinks could be increasing due to increasing biology and, depending on how co2 is distributed in the atmosphere vertically as well as latatidue, sunlight becomes more of a factor.
        3) the sun and the interaction between cloud formation and cosmic ray levels. When the sun is active, it seems to shield co2 from cosmic rays.
        4) when the planet cools, so does the co2, it sinks out, and a cooler ocean can easily absorb more.
        I have no sure answer. The warming fairies with their magic wands adjusting numbers for their models, because they just know, aren’t helping.
        When I read simplistic studies like this, it’s, do they know anything ?

  23. If climate change were caused by so called greenhouse gases then the gas of most concern would be H2O and not CO2. But there is no evidence that a radiant greenhouse effect exists anywhere in the solar system so the AGW conjecture is nothing but science fiction.

  24. I’d hypothesise that the historic atmospheric CO2 minima of ~190ppm suggests an equilibrium model in which, as the earth and it’s oceans cool, increasing amounts of CO2 is released from the oceans causing atmospheric re-warming. Accordingly it is the ocean temperature vs. ocean CO2 concentration that buttresses this lower atmospheric equilibrium. There are other variables such as significantly lowered sea levels, higher volumes of land ice which mean less sea volume to absorb CO2.

    An equilibrium for a CO2 maxima may or may not exist. Hopefully, at the point that all land ice melts, a maximum concentration of CO2 that can be absorbed by the ocean’s could be an upper equilibrium limit. But this would completely depend on absolutely no further burning of fossil fuels (or extinction of humans) and that we forests can regrow at a faster rate to act as a carbon sink. However there will be complications with ocean acidification, a much reduced land mass for those forests due to significantly higher sea levels, and a much larger sea volume to absorb atmospheric CO2.

    Unfortunately, while we can hope for a maxima equilibrium, we certainly have one, but perhaps two examples of runaway greenhouse effects that have previously occurred! Definitely Venus. And possibly Mars.

    There is no thermostat. Discussion of thermostats is just anthropomorphism. It is not science.

    • Do you… both Venus and Mars had an ocean of water. The one thing, at least that is different about the 2 is that neither one has a magnetic field. ( or very slight). Here on this planet, if you remember, the science back in the year 2000 that by now we should have been approaching a tipping point. The Bode formula that amplifies the temperature in the models requires an additional input of energy. Where are you getting that energy from ?
      Further you don’t have the slightest idea with what’s happening with the co2 sinks. So many scientific conjectures from 2000 about co2 are no longer spoken of. And the rest of the really hard questions aren’t addressed. How do you address the last 60 years of co2 following temperature? How do you address the ice core samples co2 lags temperature by 800 years ? Manipulate the data? How do you address the year over year growth of co2 by 1 billion metric tons and the co2 ppm per year is not reflected in the the current record ? Something is definitely not right. I was fully expecting that co2 ppm for 2016 to be 5 or possibly 6 ppm, from the amount of anthropogenic co2 and from an el nino. They either manipulated last year’s co2 record or there is something serious going on that no one has a clue about.
      We didn’t have a runaway greenhouse effect when co2 was 1700 ppm. Unfortunately, since that time, or fortunately for us, the world did just the opposite, it got colder.

  25. No one ever mentions 14CO2 is continuously created in the upper atmosphere during quiet sun periods.

    Anyway, can someone please point me to an explanation, real science please, of how radiation from CO2 in the cooler atmosphere can warm the much warmer earth below. It certainly can’t warm 70% of the water covered earth, so that implies, to my layman thinking, that only 30% of the CO2 in the atmosphere is doing all the currently claimed anthropogenic global warming.

  26. I would have thought this process was too obvious to get a paper published about it. It is just CO2 Fertilization Feedback (“greening”).

    People forget that it works both ways:
    1. The more CO2 there is in the atmosphere the faster plants remove it. (Reduces warming.)
    2. The less CO2 there is in the atmosphere the slower plants remove it. (Reduces cooling.)

    Negative feedbacks do not just reduce warming, they also reduce cooling. In other words, they increase climate system stability.

    There are always oxidation processes (fires, rotting organic matter, animal respiration, etc.) going on, which produce CO2. So when the photosynthesis rate drops below the point where the plants can keep up and use as much CO2 as is produced, the CO2 level goes up, causing the photosynthesis rate to increase. That feedback loop limits how low CO2 levels can get.

    Every schoolchild learns that animals use O2 and produce CO2, and plants do the opposite. But have you ever wondered why there are more than 500 O2 molecules in the atmosphere for each CO2 molecule? Nearly all of the oxygen in the atmospheres of Venus and Mars is in the form of CO2, and almost none is O2, but on Earth it’s just the opposite. Why is that?

    It is because Venus and Mars are dead planets. But on planet Earth carbon-hungry living things have used up nearly all the CO2, to get the carbon, discharging the O2 as a waste product. The plants outnumber us animals, and they used up the CO2 until they ran out, practically speaking. They used up CO2 until the level got so low that the photosynthesis rate was reduced to rough equilibrium with the CO2 production rate. It is a very obvious, very fundamental, negative feedback system. The chronic shortage of CO2 is the fundamental limit on plant growth, on planet Earth.

    This statement from the article is nonsense: “the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.”

    CO2 Fertilization Feedback works both ways. With CO2 high, as it is now, CO2 Fertilization Feedback is removing a large portion (AR5 estimates 27-29%) of anthropogenic CO2 emissions from the atmosphere, each year. The only reason that CO2 levels are continuing to climb is that we are producing prodigious amounts of CO2. It’s not that the negative feedback isn’t working, its simply that we’re currently overwhelming it with the huge amounts of CO2 we’re releasing.

    That can’t go on forever. We’ve only added about 120 ppmv of CO2 to the atmosphere, and CO2 fertilization feedback is already removing CO2 from the atmosphere very rapidly — just not as rapidly as we’re adding it. But as CO2 levels climb, the negative feedbacks which remove it operate faster and faster, making it progressively more difficult to raise CO2 levels. That’s why I doubt that mankind will ever manage to drive CO2 levels much above 600 or 700 ppmv.

    When CO2 levels go up, two things happen:
    1. The warming effect of additional CO2 diminishes logarithmically.
    2. The CO2 removal rate by natural processes, including “greening” and dissolution in the oceans, increases.

    So it is easy to see why it is an inherently stable system.

    • Venus and Mars are dead planets because there is no magnetic field to protect them from the solar wind.
      Still no word on why we had a MWP and a LIA. Outside of a Yellowstone going off, the orbit of the earth, the tilt, activity of the sun, a large rock falling out of the sky, where we are in the galaxy, it’s stable.

      • The recent warmup, also referred to as the current warm period, CWP, has implications on AGW. AGW has asserted that temperatures are solely controlled by co2. When asked about the MWP and the LIA, their answer was that it was local and not world wide. After it was shown that both were indeed world wide, the next line was that the MWP wasn’t as warm as it is now. The evidence indicates that it was warmer. And there is no question the LIA was cold.
        The problem for AGW is what was happening then to make it warmer that isn’t happening now. It obviously wasn’t co2. If it was, they’d have to point to a source. My research into the co2 record has me wondering if the co2 record over the last 1000 or so years is correct. I’m wondering if they didn’t flat line the co2 record along with the temperature line. In the last 60 years there is a delta movement in the co2 that moves with temperature. I am certain of that.

  27. {Sigh!} Pollution is a real problem, and “Eric”‘s sky-dragon-slayer gibberish is a prime example. It’s thread pollution. (Is that you, Doug?)

    [no, it’s not Doug, but another person known to us who uses fake names, fake emails, and fake IP addresses to get his inane comments through. Comments deleted due to site policy violations, thanks for the heads-ups – mod]

  28. It amazes me that it is so often overlooked that the earth itself is a heat source. Ice is also an insulator. The combination means that glaciers and ice caps are always melting from the bottom, and a ‘snowball earth’ is doomed from beneath, regardless of the composition of the atmosphere.

  29. “However, the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.”
    The mechanism to prevent rapid warming is called clouds.

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