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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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CO2 lags temperature - what does it mean?

What the science says...

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CO2 didn't initiate warming from past ice ages but it did amplify the warming.  In fact, about 90% of the global warming followed the CO2 increase.

Climate Myth...

CO2 lags temperature

"An article in Science magazine illustrated that a rise in carbon dioxide did not precede a rise in temperatures, but actually lagged behind temperature rises by 200 to 1000 years.  A rise in carbon dioxide levels could not have caused a rise in temperature if it followed the temperature." (Joe Barton, US House of Representatives (Texas) 1985-2019) - Full Statement

Earth’s climate has varied widely over its history, from ice ages characterised by large ice sheets covering many land areas, to warm periods with no ice at the poles. Several factors have affected past climate change, including solar variability, volcanic activity and changes in the composition of the atmosphere. Data from Antarctic ice cores reveals an interesting story for the past 400,000 years. During this period, CO2 and temperatures are closely correlated, which means they rise and fall together. However, based on Antarctic ice core data, changes in CO2 follow changes in temperatures by about 600 to 1000 years, as illustrated in Figure 1 below. This has led some to conclude that CO2 simply cannot be responsible for current global warming.

Figure 1: Vostok ice core records for carbon dioxide concentration and temperature change.

This statement does not tell the whole story. The initial changes in temperature during this period are explained by changes in the Earth’s orbit around the sun, which affects the amount of seasonal sunlight reaching the Earth’s surface. In the case of warming, the lag between temperature and CO2 is explained as follows: as ocean temperatures rise, oceans release CO2 into the atmosphere. In turn, this release amplifies the warming trend, leading to yet more CO2 being released. In other words, increasing CO2 levels become both the cause and effect of further warming. This positive feedback is necessary to trigger the shifts between glacials and interglacials as the effect of orbital changes is too weak to cause such variation. Additional positive feedbacks which play an important role in this process include other greenhouse gases, and changes in ice sheet cover and vegetation patterns.

A 2012 study by Shakun et al. looked at temperature changes 20,000 years ago (the last glacial-interglacial transition) from around the world and added more detail to our understanding of the CO2-temperature change relationship.  They found that:

  • The Earth's orbital cycles triggered warming in the Arctic approximately 19,000 years ago, causing large amounts of ice to melt, flooding the oceans with fresh water. 
  • This influx of fresh water then disrupted ocean current circulation, in turn causing a seesawing of heat between the hemispheres.
  • The Southern Hemisphere and its oceans warmed first, starting about 18,000 years ago.  As the Southern Ocean warms, the solubility of CO2 in water falls.  This causes the oceans to give up more CO2, releasing it into the atmosphere.

While the orbital cycles triggered the initial warming, overall, more than 90% of the glacial-interglacial warming occurred after that atmospheric CO2 increase (Figure 2).

Shakun Fig 2a 

Figure 2: Average global temperature (blue), Antarctic temperature (red), and atmospheric CO2 concentration (yellow dots).  Source.

Last updated on 21 April 2021 by eckahle. View Archives

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Further reading

That CO2 lags and amplifies temperature was actually predicted in 1990 in a paper The ice-core record: climate sensitivity and future greenhouse warming by Claude Lorius (co-authored by James Hansen):

"Changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing"

The paper also notes that orbital changes are one initial cause for ice ages. This was published over a decade before ice core records were accurate enough to confirm a CO2 lag (thanks to John Mashey for the tip).

Also, gotta love this quote from Deltoid in answer to the CO2 lag argument: See also my forthcoming paper: "Chickens do not lay eggs, because they have been observed to hatch from them".

Further viewing

Myth Deconstruction

Related resource: Myth Deconstruction as animated GIF

MD Lag

Please check the related blog post for background information about this graphics resource.

Comments

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Comments 276 to 300 out of 636:

  1. Tell me if I have this right... The 100,000 Milankovitch Cycles are the result of eccentricity of the Earth's orbit. So, interglacial periods, like the present, occur when the planet is closer to the sun.
  2. The 100,000 cycle is problematic. See here for some more discussion. I'd say the jury is till out.
  3. Responding from here The newtonian gravity situation is an n-body body, so quite definitely deterministic chaos. However, the milankovitch cycles are predictable, regular cycles at the time scales we are talking about (whether you could extend 100my back is entirely different). However, what you think of a chaotic signal is not - the spectral analysis gives that away. Set up a spreadsheet with =R*sin(a*A1]) + S*sin(b*A1) + T*sin(c*A1) where R,S,T are within an order of magnitude and a,b and c are not multiples of each other, and you get an utterly non-chaotic,predictably cycle but no repeats.
  4. scaddenp, Perhaps I'm doing it wrong. I tried (1.1*sin(2*x) + 2.2*sin(3*x) + 3.3*sin(5*x)) but what I get seems to repeat at intervals of 2*pi (minus a precision error on the order of 1e-15 or so). The reason I asked about these things is that if the clockwork Milankovitch cycle were the only driving force behind the ice ages, then I would have expected each ice age to be identical. As mentioned in the other thread and here, I guess it's not that simple -- there's continental drift, plants, asteroid strikes, volcanic activity. As far as I can tell from what people are saying here, these extraneous forces that give the jagginess to the above temp/CO2 plots are considered to be random, not chaotic. I can buy into their reasoning, though I doubt I'll ever do so wholesale. Thank you for the info! - Shawn
  5. Well a,b,c is no. of cycle repeats in 2*pi! Try say =(0.3*SIN(0.00006283*B1) + 5*SIN(0.000299199*B1) + 2*SIN(0.000153248*B1)) (which has frequencies around the milkanovich). Note no phase terms either. Now you have peaks of different size and magnitude but a very long time before they repeat (I graphed say from angle 0.01 to 710000). However, I agree though that the cycles are the major driver, a lot of other factors play as well, and yes, random, not chaotic.
  6. Since we have accepted the fact that atmospheric CO2 concentration is a primary driver of the earth's climate and also the fact the the earth has been much warmer in the past this presents a dilemma. The oceans contain about 50 times more carbon dioxide than does the atmosphere. It has been well noted that warming oceans release more of their absorbed carbon dioxide than they at the same time sink from the atmosphere. So remembering that atmospheric carbon dioxide concentrations are the primary driver of our climate any previous warming in excess of what we see in modern times should have driven a runaway warming cycle, driven by massive releases of oceanic carbon dioxide in a positive feedback loop. But somehow this didn't happen. I wonder why?
  7. A positive feedback does not necessarily mean runaway feedback. See run away warming
  8. 287: Bruce, A couple of misconceptions in your comment: CO2 is not the only driver of climate. It happens to be a strong positive forcing now; that does not mean it always was. Oceans are acidifying, meaning they are absorbing CO2 from the atmosphere. At some point (or perhaps at some locations) they will warm sufficiently to release dissolved CO2. As always, the picture is more complicated than one can sum up in a sentence or two. There is a wealth of information here at SkS designed to inform and dispel some of the myths, half-truths and outright distortions that kick around the internet. Use the Search function to browse the most commonly heard 'skeptic arguments.'
  9. This is continuation of argument in another thread. RW1 - Yes, I'm arguing the evidence doesn't support that GHGs (i.e. CO2 levels) are a significant factor in the glacial/interglacial cycle. Firstly, Timothy Chase (and the intermediate version here) challenges the idea evidence doesnt support it. Solar + albedo doesnt produce the same curve shape. Likewise how does NH change alter the SH as well? Second, this is an idea that only works without the maths. Like the idea that sealevel rise is due to more people and that they are obese. The change in DLR for the change in GHG can be calculated and the change in albedo can also be estimated. See the IPCC WG1 Chpt6 for the values of these forcing and source papers. Are you suggesting the albedo forcing is greater or DLR less? What papers support this? Actually the convincing evidence would be a physics-honouring model that can do it without GHGs but noone's been able to do that to date and they have been trying since Milankovitch.
  10. SOMETHING has buffered global warming at the apex of every interglacial warm period for the last 2 million years. Otherwise we would have reverted to the so called greenhouse climates that have dominated earth history.It would be really nice to know what that SOMETHING is.The apparent lag of CO2 behind temperature for the last 800000 years may provide a clue. Temperature has led on both the rapid recoveries where CO2 positive feedback is likely and on the slower declines to ice ages where CO2 may have acted as a brake. Whatever the SOMETHING is, it prevented CO2 from taking control of climate until possibly the last few years.
  11. trunkmonkey, I am not sure I follow. The ice-age is driven by orbital forcings. When the forcing changing to negative, then feedbacks work the other way pulling CO2 out of atmosphere. There is no "run-away" to pre-Pleistocene atmosphere (see here for more on run away feedback). It seems to me that you are postulating an unknown in ice-age model that doesnt exist.
  12. scaddenp, the orbital variations have probably been constant as long as there has been life on earth, yet glacial periods are exceptional in earth history.We're just lucky I guess? The orbital insolation variation is miniscule, on the order of a tenth of a Watt per square meter, and its 100000yr signal matches only rather crudely the glacial-interglacial periodicity.I sense were working a puzzle with missing pieces.
  13. Under "recent" times, CO2 levels have been much higher. Geological processes gradually remove CO2. When CO2 is above a certain level, you dont get a glacial cycle because its always warm enough to prevent ice build up and the feedbacks that amplify the glacial cycle. While the global forcing is very weak, the forcing at 65 is rather stronger. Land and altitude allow ice sheet build up in the NH. The 100,000 cycle IS a puzzle, but the problem (as with a lot of problems in paleoclimate) is not finding a solution but that there are more solutions than the data can constrain. Yes, there are missing pieces but the overall mechanism is understood.
  14. scaddenp: ...the orbital variations have probably been constant as long as there has been life on earth, yet glacial periods are exceptional in earth history.We're just lucky I guess? If you are going back pre-Quaternary you need to account for paleo-geography, i.e., continental drift. If you don't have a continental mass at the poles or at least enclosed around a pole as is present day, it is not likely an open ocean is going to freeze. Further consideration would be different ocean circulation and a dimmer sun.
  15. Rick G -
    if you are going back pre-Quaternary you need to account for paleo-geography
    And orography (mountain-building), and the rise of angiosperms (flowering plants). The climate models show some pretty marked cooling when these are accounted for.
  16. 294. "the problem (as with a lot of problems in paleoclimate) is not finding a solution but that there are more solutions than the data can constrain." Sad but true. The only data that can really constrain anything come from the last sixty years and everything pre satellite is sketchy. Paleoclimate is really a logic excercise where you are lucky when the disparate signals from proxies give you a correlation. What is unique about the Antarctic ice core data (although the "down under" data point is less than ideal) is that they give us independent signals for both temperature and CO2 at the same time and in the same medium. I believe that the clear signal that temperature lead CO2 in these data is an extremely important clue that is not adequately explained by Milankovitch. Invoking Occam, we should probably suppose that temperature has lead CO2 for all of earth history, or at the very least in prior glacial episodes.
  17. trunkmonkey @ 297, I see a lot of hand waving but not a bit of supporting evidence to back up anything you said.
  18. trunkmonkey - "Paleoclimate is really a logic excercise where you are lucky when the disparate signals from proxies give you a correlation." This simply not true. Uncertainty bands gets larger but you will find that alternative theories have to work with quite strong constraints. Suggest you read up on this. "I believe that the clear signal that temperature lead CO2 in these data is an extremely important clue that is not adequately explained by Milankovitch." And what is the basis of your belief? Certainly not published science. How come models using known physics have little problem with such data? As to whether CO2 has always led temperature, possibly but PETM is closer to what we had. Temperature increases will certainly lead to CO2 increases to amplify the effect but if another mechanism (eg burning fossil fuel) will increase CO2, then you still get the temperature rise.
  19. 299. "I believe that the clear signal that temperature lead CO2 in these data is an extremely important clue that is not adequately explained by Milankovitch." And what is the basis of your belief? Certainly not published science. How come models using known physics have little problem with such data? I have read most of the threads on this website and I have not seen many citations. I presume the models you refer to are GEOCARB and GEOCARBSULF (see Berner@"I believe that the clear signal that temperature lead CO2 in these data is an extremely important clue that is not adequately explained by Milankovitch." And what is the basis of your belief? Certainly not published science. How come models using known physics have little problem with such data? I have read most of the threads on this website and I have not seen many citations. I presume the models you refer to are GEOCARB and GEOCARBSULF. A good synopsis can be found at Breeker et al 2010. If I may be permitted to incorporate herein by reference all of his citations, it will save me a lot of trouble. A philosophical question: can a computer model with postulated imputs that successfully match a known phenomenon, but which has never successfully predicted anything, ever be considered to be more than a correlation, or indeed a logic exercise?
    Response: See the Argument "Models are unreliable." And post further comments about that topic over there, not here, please.
  20. 299. PS. Sorry, everything went wanky when I tried to paste the Berner citation. I think it is in Breeker anyway. I wanted to cite a specific example. Berner, in the failed citation, makes the grand arm waving statement " A large Devonian drop in CO2 was brought about primarily by the acceleration of silicate rock weathering by the development of deeply rooteds plants in well drained upland soils."
  21. Your Honor, I swear I was going to pull this back to temperature precedence, but at your guidance I will move my post script to "models", even though they may be non sequitur there
  22. I'm unfamiliar with paper you are trying to cite. Thanks to colleague who are interested in PETM and want to use my hydrocarbon maturation model to examine sedimentary basin feedback, I have suddenly had to come to speed on PETM. The models I was referring to are GCM-type models used in PMIP. See Ch 6 of WG1 for access to the enormous literature on this. I would readily agree that the relative contributions of various carbon sources and sinks are still uncertain. However, the climatic response response is well captured. The main takeaways though are: 1/ carbon-cycle feedbacks in the SHORT term (1000's of years) amplify the effects (positive and negative) of other climate forcings. 2/ The CO2/CH4-feedback in the glacial cycle is from ordinary organic carbon. 3/ The CO2 in the atmosphere today is from fossil fuel sources. 2 and 3 are evidenced from carbon isotope data. Carbon-cycle feedbacks are slow. Most AR4 models ignored them as irrelevant for next 100 years. If this is incorrect, then warming would be worse.
  23. 299.PPS. Berner is alledging here that he has some knowledge that there was a lot of silicate (read rhyolitic and granitic)well drained upland rock for the giant Gymnosperms (tree ferns) to sink their roots into 370 Ma. He goes on to alledge that he has somehow tested this in modern soils. Assuming for the moment he is correct, this might explain the decent into a glacial epoch, but not the climb out.
  24. Without reading the papers and associated evidence, I cant comment on the reliability of the data. However, as a general rule, anything "paleo" in investigation has to necessarily form an hypothesis based on what we do know and then project back into the past to see if it fits paleo data. A fit gives us confidence that our ideas are not grossly wrong but cant of course "prove" that we are right. Since this is a climate blog concerned with the more immediate future of planet, you also need to recognize the significance (and insignificance) of this work. The geological processes at work here are largely irrelevant to climate of next 100 years. However, the predictions for the next 100 year ARE dependent of a model of drawn from physics (not paleoclimate). If this model of climate is correct, then it must also work (within the uncertainities) for paleoclimate.
  25. Also, if you think paleoclimate is more or less unconstrained, invent anything, have a look at Zeebe et al 2009 on difficulties with PETM. (Doesnt begin to address the cause of carbon release but deals with other issues). Needless to say my colleagues think they have a possible solution to the conundrum posed...

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