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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.


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Comments 201 to 225 out of 639:

  1. This timescale argument is a bit silly. This IS the climate timescale. When I write sudden, I mean sudden in climate terms. Surely that's obvious? What's sudden to the climate of the earth is not sudden to a kitten. When you talk about the CO2 supply in the ocean dwindling, and turning off a feedback loop, ten thousand year would be incredibly sudden.
  2. mistermack, what is the basis for your claim that ten thousand years would be an incredibly sudden period for CO2 feedback to dwindle?
  3. mistermack, why are you claiming that the cause of reduced CO2 levels was dwindling of the CO2 content of the ocean? The ocean's role in adding or removing CO2 from the atmosphere depends on the temperature, CO2 concentration, and other chemistry in the ocean, but also on temperature and CO2 concentration in the atmosphere. Unlike in the atmosphere, CO2 in the ocean is not so well mixed, which is why its role in triggering reversal of ice ages seems to hinge on ocean currents bringing CO2-rich water up from the depths. Changes in any of those factors can change the rate at which CO2 outgases from the ocean, and even reverse the direction to absorption. Changes in any of those factors can come from any number of other factors, including change in seasonal insolation due to orbital progression. An example is that suggestion of a CO2 burp from the southern ocean being a trigger of at least one particular ice age. Burps have starts and ends. The notion is that deep CO2-rich water upwelled "suddenly." But that would have depleted that deep reservoir of CO2-rich water. So that extraordinarily high rate of CO2 outgassing would have been a "short" duration event.
  4. Tom, I would agree that a "burp" mechanism would be interesting. But it would need to be demonstrated that it could be significant on a global scale, not local. And in that case, you would expect to see a clear signal in the ice cores. I wouldn't discount it as being possibly significant, but it would need more evidence of a worldwide effect. I can't visualise a "gulp", working at the top of the cycle though.
  5. Tom, re your previous comments, the ten thousand years was my estimate, snatched out of the air, but bearing in mind that there is an 800 year lag between a temperature rise showing even the slightest rise in CO2 levels. How long would it take to significantly reduce CO2 availability in the ocean significantly? Especially as oceans should be significantly warming all the time.
  6. @mistermack: "This timescale argument is a bit silly." What is silly is your insistence to ignore all the information we provide you in order to continue pushing your agenda. There is a wealth of information for you here, but you are not interested in learning the truth, it seems. "When you talk about the CO2 supply in the ocean dwindling, and turning off a feedback loop, ten thousand year would be incredibly sudden." Tom explained it quite well. It doesn't mean that there is no more CO2 in the ocean, but that the conditions for the CO2 outgassing are no longer present. Again, the fact you don't understand the science doesn't make it invalid. Stop being so arrogantly certain that you hold the truth and start learning some actual science.
  7. Archie, you're just basically resorting to adhominems now, so I'm going to leave you to it. I'm only interested in evidence. You can hardly speak of me having an agenda, and then make ad hominem comments. That's a sign of someone who can't debate, and doesn't really understand what he's talking about, but still want's the last word. A clear sign of someone with an agenda.
    Response: Please refrain from making 'ad hominem' accusations when none are actually made. Feel free to disagree, certainly, but be respectful when doing so.
  8. @mistermack: "Archie, you're just basically resorting to adhominems now" Yeah, that's what contrarians usually say when they're out of arguments... "I'm only interested in evidence." ...but only as far as it reinforces your position, it seems. Everyone here treated you nicely and patiently provided counter-arguments, which you choose to ignore. "You can hardly speak of me having an agenda, and then make ad hominem comments." I (and others here) have been quite patient with you, even when you made an ad hominem attack upon basically everyone who chooses to study in Climate Science, so spare me the fake outrage. "That's a sign of someone who can't debate, and doesn't really understand what he's talking about, but still want's the last word. A clear sign of someone with an agenda." Wait, are you talking about yourself now? It sure can't be me because: a) I can debate just as well as any other poster here; b) I try to only talk about things I understand, and have no problem admitting when I'm wrong (I've done that a couple of times on this very site); c) doesn't feel the need to have the last word any more than you. As for my agenda, it's quite simple: I'm interested in learning more about Climate Change (I learned tremendously here, because unlike you I came with an open mind), and I don't like when I hear the same debunked theories against AGW again and again, especially when we know who's behind the disinformation - not saying you are, of course. I'm giving you the benefit of the doubt and think you're actually just wrong. I apologize if you feel insulted, and I assure you I mean nothing personal by my criticism. I simply ask you in good faith to look on the evidence presented on this site and not simply dismiss it off-hand. That's still the best thing about this place. :-)
  9. Archie, you took to criticising the person, not the argument, in your previous post. That's what I meant. I would just say to you, it's a bit like religion. It doesn't matter what you believe, or me. Nor what we say. It won't change the fact. Either warming is mostly man-caused, or it isn't. Nothing I say will change that. If you want to achieve a comment section with everone agreeing, it's not going to make great reading. But at least you will have a consensus.
  10. @mistermack: I criticized your behavior, and your insulting insinuations against people who choose to study climate science. I did criticize your arguments, but it can get pretty frustrating when one side gives the appearance of not wanting to debate in good faith. People here have been quite patient with you, perhaps you should show the same consideration to others and not take such an adversarial tone, especially when every one of your arguments have been successfully rebutted. The goal of this site is not to provide "great reading," it's to present the actual science to those who want to learn more, and to counter the disinformation and bad science spread by a vocal minority on the Internet. As far as the consensus goes, I think I made my position clear in the other thread.
  11. Archie, I'm leaving it there. I can't be doing with all this emotional stuff. Bye.
  12. Re: Tom Dayton (149, 203) and mistermack (150, 204) Interesting & germane new article out in nature geoscience today, "Southern Ocean source of 14C-depleted carbon in the North Pacific Ocean during the last deglaciation". Germane, as it adds weight and evidence to the "burp" mechanism under discussion. Interesting also was the development of neodymium isotope values as a proxy. Science Daily write-up here. The Yooper
  13. This doesn't really strengthen the sceptic argument, but I've noticed in the graph above that the CO2 timelag is pretty obvious most of the time, EXCEPT for the apparent runaway warming phase, out of the coldest ice-age, right up to the hottestp peaks. Maybe it's there, but not obvious in that graph, or maybe there is no lag for that runaway warming phase. If so, I would find that very interesting indeed. If CO2 doesn't lag temperature for that period, it would seem that something else is causing the release of CO2, maybe on top of the rising temperature. Something to do with fresh water meeting saline, perhaps?
  14. I don't buy this theory. External event rises temperature. Soils and vegetation release co2 in a global burnoff. Probably the ocean mass heat memory with dissolution is the likely explanation of the centuries delay. If co2 amplified minor temp rises then it should be in synch without delays of centuries. Eventually the temperature goes down and the plants etc can reabsorb the gas back to photosynthesis equilibrium levels. You never get the amplification process because photosynthesis is such a dominant process. Perhaps when the conc goes above 1 per cent is co2 greenhouse effect sufficient to influence temperature. Look if co2's lifetime was several centuries then do the calculation of 100 years of fossil consumption with 5gt per year for the last 20 years. What should the co2 concentration be? I don't know the mass of co2 in the air currently, but some have done it and say that half the mass is missing, ie perhaps a 20 year lifetime, some say 5. This stuff is scrubbed from the air.
  15. #214: "... co2 greenhouse effect sufficient to influence temperature." Try to substantiate your claims, rather than just make such declarations. You might want to do some reading before you engage in so many blanket dismissals. Start here, here and here, then we can talk.
  16. @cgp: "I don't buy this theory." I do, as do most people who understand science. You see, the theory has a lot of evidence supporting it. I have yet to see any evidence for your claims. I second muoncounter's suggestion: learn more of the actual science before making such unsupported claims.
  17. CO2 is a very SLOW feedback from temperature increase. I dont think any AR4 model include it as a feedback. Actually we do know the mass of CO2 in the air, and yes, nearly half of our emissions are being mopped up - but half arent. However, what happens when the sinks are saturated? What makes you think photosynthesis is dominant over oceans as a CO2 sink? Have you done the maths and if so how does it compare with result of others eg here or here
  18. After reading the three years of arguments relating to this question, I still can't form a definitive conclusion in my simple, non-scientific mind. It seems to me that John Cook's rebuttal is an execellent answer but it doesn't go far enough and raises more questions in my mind. It now seems clear that GW is the cause of the increased CO2 in the atmosphere which assisted now by mankind. But the questions are: Firstly, what is the mechanism for the reversal of global warming? Is this when the CO2 levels in the atmosphere reach saturation? Secondly, is the level of CO2 in the atmosphere related to the degree or the length of the GW? These questions seem critical to me since if there is a saturation level then mankind's addition to the levels or to the speed of accumulation of atmospheric CO2 are irrelevant.
    Response: In the Search field at the top left, type "saturated."
  19. Re: MikeC (218)
    "Firstly, what is the mechanism for the reversal of global warming? Is this when the CO2 levels in the atmosphere reach saturation?"
    Two part answer to that: 1. CO2 long-term drawdown is by chemical weathering (hundreds of thousand year timescales) and by biological sequestration (oceanic life forms sinking into the deeps). After CO2 is in the upper atmosphere, residence time is on the order of millennia, essentially. See here and here. 2. The globe is warming because the Earth's radiation budget is out of balance. All things being equal, as long as mankind is adding sequestered carbon back into the carbon cycle, the energy budget will be imbalanced and the warming will continue. If CO2 emissions were cut to zero and held there, warming would still continue for several decades (due to the thermal lag of the oceans) until an equilibrium was reached.
    "Secondly, is the level of CO2 in the atmosphere related to the degree or the length of the GW?"
    See answer number two above. Then consider this: The GHG effect means adding CO2 will raise temperatures globally. By how much is a function of climate sensitivity. A doubling of CO2 concentrations from pre-industrial will yield a temperature increase of about 3 degrees C considering short-term effects (less than 100 years). Long-term feedbacks may add another 2-3 degrees C warming on top of that (withing the next several centuries). Barring some form of Carbon Capture Sequestration (CCS), warming is not a transient effect (no more ice sheet advances for the next 30,000 years). A warming/warmer world is here to stay, from the standpoint of human timescales. The Yooper
  20. #218: "now seems clear that GW is the cause of the increased CO2 in the atmosphere" I wonder how exactly that works. Warming increases CO2? Where does it come from? Why did rapid warming start well after the rapid buildup in atmospheric CO2 that began after WW2? Or is that the preconceived notion you came in with?
  21. Unfortunately, this article is in need of some serious revision -Deglaciation is not initiated by CO2 but by orbital cycles -CO2 amplifies the warming which cannot be explained by orbital cycles alone <---weak reasoning! -CO2 spreads warming throughout the planet These points are about as logical as "collect underpants > ? > profit!", where the '?' here is analogous to the middle point above. Obviously change in orbital cycles alone does not account for all temperature fluctuation, and neither does orbital fluctuations + CO2. There are many feedbacks. As horrible as it may sound, you can't win them all. CO2 may or may not be causing modern day warming, but if you think you can spin the fact that causation is reversed historically into proof that CO2 is causing warming you're delusional. At the least you should provide some further links to back up the middle point, but really what needs to be done is to change the article to concede that yes, historical causation does support the skeptical side, but may or may not be relevant now that CO2 concentration is being altered by humans as well as the carbon cycle. To claim anything more is extremely disingenuous.
  22. hurleybird I'm just a layman, but it appears to me that you would need to refute over 100 years of physics and chemistry to disprove the greenhouse effect.
  23. Hurleybird, You need to be more specific in your argument, as your last post contained not a single science-based refutation. "I don't believe it" is not an acceptable response to the role of CO2 as a forcing or feedback, nor does it address the validity of our understanding of Milankovitch Cycles. The Earth's tilt towards the sun changes. The planet warms. Warming oceans release CO2 into the atmosphere accelerating the warming process. What part of this do you have a problem with?
  24. I have just noticed this site and will read submissions on it with interest. I have a simple question. Dr. Roy Spencer [ ] who I am sure, needs no introduction, has just posted a comment "Show me one peer-reviewed paper that has ruled out natural, internal climate cycles as the cause of most of the recent warming in the thermometer record." Any offers for him?
  25. Alleagra, Wow, Spencer is doing a merry dance...and the goal posts keep shifting so much and so far that it is a wonder anyone can keep up...perhaps that is the point. How about this please show us a peer-reviewed paper (published in a reputable journal please)which demonstrates that most of the observed warming to date is from natural forcing. I do know of a paper off the top of my head which addresses his loaded question (sounds like a similar situation to Lindzen cherry-picking 1995 in the HadCRUT record), but I will have look. I suspect Spencer has scoured the literature and carefully formulated his question so as to try and claim a "gotcha". We'll see...

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