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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 76 to 100 out of 119:

  1. On average, the climate of the last quarter million years have been very much less hospitable to humans and all life in general. It is less than 20% of time that the climate stay hospitable. Should humans allow the climate to naturally ebb back into terribly inhospitable cold? Do we actually know the mechanisms humans can use to delay the onset of the next apocalyptic ice age? Isn't the prevention or delay of ice ages terribly more important than slight rises in temperature? Do the druids and "humans should have no climate impact" scientists agree that allowing the globe to slip into the next ice age would be a bad thing? Somehow, I don't think so. Beavers had dramatic impact on climate and terrestrial life: If they had become smart enough to become self aware, should they have stopped transforming the planet?
    Response: The possibility of heading back into another ice age has been examined on multiple occasions in the peer-reviewed literature. Ice ages begin when northern ice sheets encroach further southward from year to year, gradually increasing the Earth's albedo. So if a huge ice sheet takes over northern Canada, then yes, be concerned.

    But in the meantime, the two largest ice sheets in the world, Greenland and Antarctica, are losing ice mass at an accelerating rate. You can rest assured that the imminent ice age has been postponed indefinitely. On the contrary, the accelerating mass loss from these ice sheets is predicted to raise sea levels by 1 to 2 metres by the end of this century. For the sake of my 10 year old daughter, I'm more concerned about the 1 to 2 metres sea level rise she'll see in her lifetime than a hypothetical ice age that will arguably occur hundreds of thousands of years into the future.
  2. Use of the phrase "arguably occur hundreds of thousands of years in the future" is only consistent with your quoted scientific projections if and when the CO2 release reaches 5000 gigatonnes. Are you proposing that we should reach that level? Your reference to your daughter seems inconsistent with your stated posting policies.
    Response: If we emit 5000 gigatonnes of CO2, the ice age is postponed indefinitely. If 1000 gigatonnes, then still over 100,000 years. We've already gone past the 300 gigatonne mark which will postpone the ice age for at least 50,000 years. If you want to haggle over numbers, let's adopt the most pessimistic worst-case-scenario and say we're staring down the barrel of an ice age in 50,000 years.

    I'm not sure which posting policy I've violated - it seems fairly straightforward that immediate generations are a higher priority than descendents over 5000 generations away.
  3. The study you quote only indicated half a million years for 5000 gigatonnes. (And note these are just projections). Please reference the peer reviewed article that claims to know that the next ice age will definitely not occur for the next 50,000 years. Using your daughter is clearly an emotional argument- any scientist can recognize that. Is this a forum for emotional arguments? Why won't you answer the question about the beavers?
  4. njthinker: An article by Berger and Loutre (2002) explained why this interglacial could last 50,000 years past today. The exact number of thousands of years is estimated differently by different researchers; 50,000 is the current best estimate, but nearly all researchers agree that the number is in the tens of thousands of years from now, and all researchers agree that the number is many thousands of years from now. You can learn more about the triggers of ice ages by entering "Milankovitch" in the Skeptical Science "Search" field at the top left of every page.
  5. nhthinker writes: Please reference the peer reviewed article that claims to know that the next ice age will definitely not occur for the next 50,000 years. "Definitely" is not a word that's used much in the geosciences. The last couple of interglacials were relatively short, but in recent years people have realized that neither of them is a particularly good analog for the Earth's current orbital geometry, and that comparison to the MIS-11 interglacial is more apt (Berger and Loulette 2002). Even without any anthropogenic CO2, this yields a long interglacial followed by a descent into glacial conditions around 50k years from now: Long-term variations of eccentricity (top), June insolation at 65°N (middle), and simulated Northern Hemisphere ice volume (increasing downward) (bottom) for 200,000 years before the present to 130,000 from now. Time is negative in the past and positive in the future. For the future, three CO2 scenarios were used: last glacial-interglacial values (solid line), a human-induced concentration of 750 ppmv (dashed line), and a constant concentration of 210 ppmv (dotted line). Simulation results from (13, 15); eccentricity and insolation from (19). (Berger and Loulette 2002). See also the subsequent work by David Archer, described in his book The Long Thaw and in various papers, such as Archer et al. 2005. Archer notes that the projected insolation will come close to the apparent threshold for glaciation in a few thousand years, then move away from that threshold and not cross it until 50k years from now. If our understanding of that threshold is correct, it's possible that a mild return to glacial conditions could start in a few thousand years from now. But the most likely scenario is that it won't happen for another 50k years. That's without additional CO2. Here's what Archer et al. 2005 say about adding CO2: "Release of 1000 Gton C (blue lines, Figure 3c) is enough to decisively prevent glaciation in the next few thousand years, and given the long atmospheric lifetime of CO2, to prevent glaciation until 130 kyr from now. If the anthropogenic carbon release is 5000 Gton or more (red lines), the critical trigger insolation value exceeds 2 s of the long-term mean for the next 100 kyr. This is a time of low insolation variability because of the Earth’s nearly circular orbit. The anthrogenic CO2 forcing begins to decay toward natural conditions just as eccentricity (and hence insolation variability) reaches its next minimum 400 kyr from now. The model predicts the end of the glacial cycles, with stability of the interglacial for at least the next half million years (Figure 3c)." nhthinker writes: Why won't you answer the question about the beavers? I'm not sure I understand your point. If your comment above is imagining a hypothetical situation where beavers become intelligent, industrialize, and start to double to CO2 concentration in the atmosphere, then yes, once their scientists understood the probable climate impacts of their activities they would probably be well advised to modify their ways and develop better technologies.
  6. Whoops, Tom has the name right and I have it wrong. It's Berger and Loutre, not Loulette. And when I write "If our understanding of that threshold is correct, it's possible ..." that should be incorrect not correct. Sorry for the confusion.
  7. nhthinker writes: Using your daughter is clearly an emotional argument- any scientist can recognize that. Is this a forum for emotional arguments? I don't see any problem with John mentioning his daughter. Many of us who are scientists do in fact have young daughters, and being normal human beings we may be a bit more motivated in our work by the desire to make the world a better place for them to grow up in. In any case, it seems less problematic than your own use of "apocalyptic ice age" and "druids" above. Maybe when you're just starting out participating here you might want to be a little less confrontational? Just a suggestion.
  8. What problem do you have with use of the term "apocalyptic" to describe the hostility to life of the next ice age? Do you know of an adjective that would be more accurate to describe a planet that has lost 80% of its biomass to premature death and starvation? You carefully avoided the answer as to whether humans should do what is scientifically necessary to prevent the next ice age. (A response like "we're doing it anyway" is not an answer). I assert that humans should intentionally do what ever necessary to prevent the next ice age. It should be done with a significant safety margin of error to account for unusual but expected events like massive volcanoes and asteroid hits. Do you disagree? If so, why? If there is full agreement from scientists that humans should, for the good of future generations assure that an "unnatural" amount of CO2 should be kept in the atmosphere to prevent an ice age, then who decides what the right added level should be? Those that are only concerned and emotionally connected with their immediate offspring? Or those that have a more balanced concern with the long term? Were the dramatic changes to climate/environment caused beavers considered "natural" because the they were not self-aware of their impacts? Are the changes to the environment changed by self-aware beings any less natural? To see a difference between the beavers and the humans is to agree with the druids.
  9. Nhthinker, you've been provided with excellent information indicating that perhaps 40,000 years from now we should consider another ice age to be reasonably imminent. Right now we have a more urgent problem erupting under our feet, multiple lines of evidence indicating we're in some degree of difficulty due to C02 pollution. Why not check back here in, say, 35,000 years? Meanwhile the rest of us will get on with solving the present issue.
  10. nhthinker, what you're now focusing on is a policy question that is off topic for this thread on CO2 lagging temperature:
    I assert that humans should intentionally do what ever necessary to prevent the next ice age. It should be done with a significant safety margin of error to account for unusual but expected events like massive volcanoes and asteroid hits. Do you disagree? If so, why?
    I'm not sure whether there is an appropriate thread on this Skeptical Science site, since this site focuses on science rather than policy. But you might try The Upcoming Ice Age Has Been Postponed Indefinitely, or maybe Are We Heading Into A New Ice Age? Please don't be upset if off-topic posts get deleted from any of the threads, though.
  11. The entire purpose of this forum is to link to scientific literature that human introduced CO2 is causing global warming and the clear implication here is that extra CO2 is a bad thing. The inability of scientists here to discuss what the "right amount" of extra CO2 is the appropriate amount to balance the short term needs versus the long term needs of humanity seems like a very unscientific approach to me. You are welcome to call it "policy" question. To me, it clearly has its roots in scientific exploration of causes and effects and near term disasters versus long term disasters. But it's your site and you are welcome to limit it to discuss the limited inquiry you want. Cheers.
  12. nhthinker writes: What problem do you have with use of the term "apocalyptic" to describe the hostility to life of the next ice age? Well, it's awfully slow for an "apocalypse" since it develops slowly over a period of tens of thousands of years. Also, of course, humans have already lived through multiple glacial/interglacial cycles and in fact dramatically expanded our geographic range, our population, and our behavioral development (language, tool usage, etc.) right smack in the middle of the last glacial cycle. Do you know of an adjective that would be more accurate to describe a planet that has lost 80% of its biomass to premature death and starvation? Source, please. Where does that 80% come from? "Premature death and starvation" seems a bit overdramatic for something that only transpires slowly over a period of millennia. You carefully avoided the answer as to whether humans should do what is scientifically necessary to prevent the next ice age. (A response like "we're doing it anyway" is not an answer). Again, I'd recommend a little more politeness and a little less confrontational style. I haven't avoided any question in this thread. We are, of course, actually in an ice age. As I understand it we're near the start of an interglacial that would probably last for another 50,000 years even if we didn't burn another kg of coal or oil. To answer your question directly, I don't think we should lift a finger to "prevent" the next glacial advance. I think our descendants 2000 generations in the future should be able to decide how they want to handle it. In fact, if burning fossil fuels and raising the CO2 concentration of the atmosphere were the best way to prevent a future glacial advance, that would be all the more reason to reduce our consumption of fossil fuels now and save some for the future generations who will really need them, right? Following your logic, we're currently wasting precious resources that will be desperately needed by our 2000x-great-grandchildren in AD 50,000. More to the point, worrying about the next glacial advance (which almost certainly won't happen for 50,000 years, and if we burn enough carbon may not occur for 500,000 years or more) is rather foolish when the next century or two will experience serious environmental problems caused by too much warming and the resulting alterations of the hydrologic cycle. What you're suggesting is analogous to worrying about flooding in the middle of a drought. We should focus on more immediate concerns.
  13. nhthinker writes: The inability of scientists here to discuss what the "right amount" of extra CO2 is the appropriate amount to balance the short term needs versus the long term needs of humanity seems like a very unscientific approach to me. The fact that people don't choose to discuss things in the way you want doesn't imply any "inability" or "unscientific approach" on their part.
  14. Actually, the purpose of this site seems to be to cite scientific literature that CO2 from humans causes warming and warming in the short term is necessarily bad. That there seems to be an aversion to discuss why some level of human caused CO2 may be necessarily good and an aversion to interest in understanding what that level would be seems like it has some non-scientific motivations to me. If you are interested in CO2 but not interested it what the optimum level that the humans should keep in the atmosphere to balance all the potential disasters, seems kind of limited scope of inquiry to me. If you want to take the position that the "right" level of CO2 would be the level that would occur without humans, then say so. Such a position does not have a scientific basis unless you consider humans unnatural.
  15. Science doesn't tell us what is "good" or "bad." Those are value judgments. Science tells us "If you increase the radiative forcing from greenhouse gases, the planet will warm." Whether that's good or bad, or more likely some mixture of both, depends on your viewpoint. Your repeated insistence that you want people to focus more on value judgments while simultaneously insisting that you want the discussion to be more scientific seems irreconcilable to me.
  16. Most scientists care about what the impact of their scientific inquiry is. So we get pleadings about saving the planet for a scientist's 10-year old daughter and let the future generations fend for themselves. But I guess you don't consider that a value judgment as long as its coming from a scientist "on your side". If you want to leave the impression that you think there is no amount of human caused CO2 that would be good, then you have successfully left that impression without actually saying it. But it certainly does not seem that it is coming from scientific curiosity when you make a choice not to consider the question of whether there is any amount of human induced CO2 that could be considered valuable to the environment as a scientifically valid question. One would expect that you as a scientist studying CO2 should be at least be glancingly interested in the answer to such a question.
  17. nhthinker, actually you should be satisfied by the interest of climatologists on "the impact of their scientific inquiry", at least for what concern next century. Some of them also addressed the not-so-pressing problem of next ice age tens of thousands years ahead. And, finally, the impact of ongoing climate change has been addressed regionally, some winners and some loosers in the short term, only loosers in the BAU scenario in the long term. All of these things has been put on the table for the wider audience to be able to decide what to do. I really don't get about what you're complaining.
  18. nhthinker - the issues associated with human-induced climate are about RATE of change. Who knows what an "optimal level" of CO2 is? What we do know is that changing the climate too fast is highly undesirable. Suppose you decided that 3 degrees would be better earth, would avoid an ice age etc. What you then have to decide is how fast is it safe to make that change over. The environment is stressed by change from ice age to interglacial but not too bad. If you accept rate as safe, then we need to by changing the temperature at around 1/10 of rate we are doing so at the moment. Also, I think such engineering is premature. Your efforts would reduced by natural sequestration by the time you needed it. A safer strategy would be as Ned said. Hold your carbon reserves for a few thousand years (or whatever the optimal point is) and then burn them - SLOWLY.
  19. scaddenp- Thanks very much for your thoughtful assessment. As to abrupt changes changes- sometimes they occur naturally- Volcanoes and asteroids come to mind. Thus having the CO2 in the atmosphere prior to the occurrence of the abrupt cooling event may be necessary to speed the rewarming. How fast can humans safely add CO2 to the atmosphere? I'm not sure there is good analysis on this. The current modern temperatures are still significantly less than the highs of the previous interglacial periods.
  20. The fossil record would indicate that abrupt change is very bad, not that it doesnt happen. Asteroids especially come to mind. Single volcanoes certainly make short term changes to temperature but the aerosols are short lived. There is evidence that climate change due to mass volcanism is also highly undesirable. (from the point of view of species that went extinct). The natural ice age cycle has rates that are a/ very slow compared to current change b/ entirely predictable. While I don't know what you regard as "good analysis" of CO2 addition rate, you should be making some risk assessments. The various economic analyses of cost have considered sea level rise of 1m by 2100. The effects of water-cycle disruption are harder to assess but that is what IPCC WG2 is all about. Have you read it? Does that sound "safe" to you? Whether the temp. now are less than previous interglacial periods is irrelevant- in the past those temperatures were reached with warming rates much lower than now. Rate is far more important than absolute level because adaptation takes time.
  21. Just to further clarify that. I would accept as reasonably safe, CO2 increases such that rate of temperature change was no faster than that due to Milankovich solar forcings. ie a lot lower than what we doing now.
  22. nhthinker, you did write something that does have appropriate threads on this site: "But it certainly does not seem that it is coming from scientific curiosity when you make a choice not to consider the question of whether there is any amount of human induced CO2 that could be considered valuable to the environment as a scientifically valid question." Your comments in that regard would be on topic in either of these threads: Global warming is good, which lists side by side the claims of positives and negatives of global warming or CO2 is not a pollutant But further comments on this thread you are reading now, probably will be deleted if they are off topic.
  23. nhthinker, before you post a comment, you should evaluate whether it is on topic for that thread. You should look through the list of Skeptic Arguments to find the most appropriate one. On the left side of every page there is a big thermometer. At the bottom of the thermometer there is a link "View All Arguments...." Click it to see the full list of links.
  24. The quote of Barton is taken out of context: the full paragraph was: "Current CO2 levels are around 380 parts per million (ppm); in the past, CO2 levels have exceeded 1,000 ppm [iv]. 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 [v]. A rise in carbon dioxide levels could not have caused a rise in temperature if it followed the temperature. The president of the National Academy of Sciences also testified under oath before the Energy and Commerce Committee on this very issue. " reference [iv]: "Science 22 July 2005: Vol. 309. no. 5734, p. 532 DOI: 10.1126/science.309.5734.532n This Week in Science The Eocene was an extended interval of warm climate that lasted from 55 million years ago (Ma) until 34 Ma, when permanent ice sheets developed in Antarctica. Pagani et al. (p. 600, published online 16 June 2005) present a proxy record of atmospheric CO2 concentration for the middle Eocene to the late Oligocene (~45 to 25 Ma), based on the stable carbon isotopic composition of alkenones, a type of molecule produced by certain marine algae. The levels of CO2 during the Eocene ranged from 1000 to 1500 parts per million (ppm), and then rapidly decreased to modern levels of 200 to 300 ppm by the end of the Oligocene. These data have implications for understanding issues such as the expansion of ice sheets and the development of terrestrial C4 photosynthesis." reference [v]: "Science 12 March 1999: Vol. 283. no. 5408, pp. 1712 - 1714 DOI: 10.1126/science.283.5408.1712 Ice Core Records of Atmospheric CO2 Around the Last Three Glacial Terminations Hubertus Fischer, Martin Wahlen, Jesse Smith, Derek Mastroianni, Bruce Deck Air trapped in bubbles in polar ice cores constitutes an archive for the reconstruction of the global carbon cycle and the relation between greenhouse gases and climate in the past. High-resolution records from Antarctic ice cores show that carbon dioxide concentrations increased by 80 to 100 parts per million by volume 600 ± 400 years after the warming of the last three deglaciations. Despite strongly decreasing temperatures, high carbon dioxide concentrations can be sustained for thousands of years during glaciations; the size of this phase lag is probably connected to the duration of the preceding warm period, which controls the change in land ice coverage and the buildup of the terrestrial biosphere." ---- Barton was correct in the context of his statement. The author of this article produces a strawman based on intentional or accidental overly terse quoting of Barton. It's usually easy to beat up a strawaman. If you have a appropriate quote that indicates a skeptic that claims if a condition was not a cause in some cases that it can't be the cause in any cases, then I would appreciate it if you would provide it.
  25. I'm not sure why you think this is a straw-man argument, or what difference you think the context makes. The first sentence and reference (iv) are about something else entirely (CO2 levels during the Eocene/Oligocene). That's more or less the argument dealt with on the page Does high levels of CO2 in the past contradict the warming effect of CO2? although it's talking about different times. In any case, that has nothing to do with the Pleistocene glacial/interglacial cycles Barton refers to in the second and third sentences. John quoted those two sentences in their entirety. the only thing missing is the footnote and the reference to testimony by someone from NAS. So what's your complaint? The footnote is just providing evidence that a lag occurred. But everyone agrees that the lag occurred, in fact since the warming/cooling was started by orbital forcing it would be very strange if there wasn't a lag. The problem with Barton's statement is that during the glacial/interglacial cycling CO2 acted as a feedback whereas now we're adding it directly to the atmosphere so it acts as a forcing. What exactly is your complaint? In what way is Barton being misrepresented? Can you be more specific about what you think is the problem?

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