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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 26 to 50 out of 78:

  1. I am a layman, but I thought that there was supposed to be more temperature increase in the troposphere (I think) rather than at the surface if the driving force behind rising temperatures was really CO2 levels. In fact I am told the reverse has actually been observed. Doesn't this suggest that something other than CO2 has driven most or all of the warming of the last 30-40 years?
    Response: RSS satellite data of troposphere temperature shows good agreement with models, having a slightly larger warming trend than the surface. UAH data has a slightly lower warming trend. The difference is due to how they adjust their data. What we expect to see in the troposphere and what we observe is within data uncertainty.
  2. But this isn't supportive to the greenhouse hypothesis though is it? An absence of statistically signifcant readings on a measure that is quite central to the mechanism of how a phenomenon works can be blamed on poor data, of course, but this absence while providing no particular support to the contrary, doesn't exactly provide positive support to the greenhouse argment. Or is it possible to say with some confidence that one of these two data sets is better than the other? (Although even the "supportive" data set is not able to disprove the null hypothesis of no greenhouse effect from what you say.) [Apologies if this was the wrong page on the site to have raised this subject - at the time I began I didn't realise how extensive the site was].
    Response: The relevant page is satellite measurements of troposphere. UAH vs RSS is discussed there.
  3. John, I've tried to understand how the paleo ice records are anything more than anecdotal. Problem is I've seen counterveiling studies that show that light oxygen - a direct proxy for water vapor - shows a more-consistent correlation with paleo temperatures than CO2. The ice ages hit an arid maximum and the thaws always saw a large increase in humidity as ice-locked water was returned to the hydrological cycle. It makes sense that CO2 played a role in the interglacials but the discontinuities I see in the record seem to disprove an absolute temperature-driving record for CO2. I mentioned the same thing on Watts' blog:

    Take a look at this Vostok ice core: The CO2 levels associated with past interglacials is 180 to 300 ppm, well below where we are now. 325 kya when CO2 went from 200 to 310 ppm, what did the temperature trend show? It shot up 3 or more degrees, didn’t it? The problem is that contemporary CO2 levels were already at 280 ppm during the Little Ice Age and have risen to 385 ppm; however, we’ve yet to see any hint of an equivalent temperature trend, not even latent heat in the seas (oh sure, there’s some, but it’s not piling up at the rate predicted). OTOH look at this chart: Light oxygen, isotopic Oxygen-16 is used to reconstruct paleoclimate b/c glaciers lock up light oxygen and reaches a minimum as ice ages reach an arid maximum. image006.jpg If you superimpose the light oxygen data (flip & stretch) over the past 200ky, (that’s easy to do even with MS Paint) you’ll see that the light oxygen trend line matches more closely to the paleo temperature trend than does the paleo CO2 trend where CO2 & temperatures periodically slip out of tight correlation (between 80 - 110kya and 160 - 180 kya). ( superimposition of the light oxygen chart over the vostok chart). Eyeball analysis time: There are two discontinuities between CO2 & temperature that aren’t discontinuities between Light Oxygen and temperature. Can you see the point? B/c of its evaporative and water-forming nature, light oxygen availability is a direct reflection of water vapor concentration in the atmosphere. So what’s the dominant driving agent? Is it CO2? Is it water vapor? This is why climate agnostics aren’t won over by the pro-AGW paleoclimate studies, they seem anecdotal. If CO2’s effect were consistently strong (and it’s causes steeper temperature changes at lower concentrations) then temperatures would follow more closely to the CO2 line, but they don’t, temperatures follow the water vapor line (and vice versa). What CO2 effect there is is inconclusive. CO2 may play a role, but it isn’t dominant throughout the paleo record. Just b/c it correlates doesn’t mean it causates. Our current 380 ppm CO2 level isn’t reflected by the paleo data, contemporary CO2 levels have surpassed the level of spectral absorption that has been claimed to have caused that much warming in the paleo record. And the more CO2 is added to the air, the less additional effect it has in a trend of progressively diminishing returns. Something’s inconsistent with the theory that CO2 drives temperatures.
  4. “As Congress prepares to debate new legislation to address the threat of climate change, opponents claim that the costs of adopting the leading proposals would be ruinous to the U.S. economy. The world’s leading economists who have studied the issue say that’s wrong”
    The world's leading economists? Have they mentioned the imbroglio brewing over in Europe, the ongoing rebellion in Britain? In the EU the Europeans are looking at their carbon tax overheads and realizing that they could lose their steel firms to Asian steel makers. This is b/c of the market-distorting effect of carbon taxes levied on developed nations that are not levied on developing ones. In England the additional green taxes saw "Red Ken" get ousted from the mayoral seat of London, where Ken Livingston saw the election as largely a green referendum. It was alright, an anti-green one. Labour is hammering Brown to relinquish some of the additional green taxes on trucking firms, etc. Only three countries in Western Europe have met their Kyoto targets, Sweden & France using nuclear power and Switzerland from hydro. And Japan - one of the most energy-efficient countries in the world - has simply said it cannot afford the Kyoto targets.
  5. Icebert; You will be fascinated to read Freeman Dyson's review of Norhaus' economic model of the next century of consequences to various GW solutions, taking GW as given. Among other intriguing findings: Kyoto makes little net difference; Gore's solutions are the Full Monte disaster; and the optimum is a "low-impact backstop" alternate carbon-free technology. Enjoy!
  6. Errata: Nordhaus. And a comment: I think what falls out of this is that CO2 is simply irrelevant, except insofar as it supports increased plant growth, and costs resources in a futile attempt to control it. If it made any difference, maximizing it to prevent Global Cooling would be a good idea, but ...
  7. If the following assertion is true: "The CO2 record confirms both the amplifying effect of atmospheric CO2 and how sensitive climate is to change." Then how can the downturns of the cycle, cooling, be explained in the presence of the elevated and lagging CO2? The hypothesis: Milankovitch cycles warm the oceans, and release C02 which amplifies the warming. That explains why C02 lags initial warming, and also causes the overall increase. However, this does nothing to explain the temperature decrease. With so much C02 driven temperature increase, how could temperature possibly decrease in the cycle? What is the feedback mechanism? The arguments above explain only half the model, and describe a system that would spiral to out of control heating until leveling. These arguments fail to explain the cycle's cooling phase. Without a convincing answer to that, the assertion that C02 has a causal relationship to temperature is false.
  8. What about life? As temperature rises, so does metabolism..end result more plants/animals ( as long as other conditions allow) More plants, especially soft (non-woody) tissued, release more CO2. Plant decomposition accelerates adding methane to the atmosphere. temp goes up a bit more. CO2 rises a bit more, plants flourish. More ruminants = more methane, more CO2. Cycle continues until you start locking up CO2 in woody plants. I'm not saying this is THE cause, but it is a factor to be considered and allows CO2 to lag T and then decline as forests develop (800 - 1000 years grows an awful lot of woody material)until (possibly!) CO2 levels begin to fall. Also we should stop talking about variations in insolation being irrelevent. They aren't. The direct physical effect may be small...but the consequencies of that small effect may well be pretty big.
  9. Mizimi Astute observation. Much more credible than the "consensus" view as Methane actually is a GHG with more potential than CO2. But another factor is ocean and air currents that differ depending on location of the continents and locations of internal thermal forcing which I refer to as vulcanism (old habits die hard) that cause upwellings in the oceans constantly altering currents.
  10. In other words, to alter the climate drastically, the earth must be altered drastically.
  11. QM: Couldn't agree more. Climate records ( direct or proxy) indicate small changes until you get to some truly massive an asteroid strike. This gives me comfort in the general stability of our climate; the issue then becomes one of degree. Any AGW effects have to be examined for the degree to which they may affect climate, not for the absolute change. Oceanic currents, atmospheric currents are simply means of distributing/modulating heat flow; the whole system is a thermal model Heat in - Heat out which is modulated by a variety of factors ( and I don't like the use of the word 'forcing' because it carries other overtones) which we do not (yet) fully understand. Incidentally, domesticated ruminants are estimated to produce 36Mtonnes of methane annually; the New Zealand government is introducing a 'emissions' tax on livestock farmers .........
  12. Mizimi The AGW argument here is based on the fact that TSI stopped following the temp curve in 75 or 76. And they are right on that account, it did. So we know solar forcing has the capability but what happened in 1975-76? The single major event was a full (once in a lifetime) solar alignment. It won't happen again for a very long time. The results were not immediate but started within a few years of the event. The earth became active, plate movement increased speed, new volcanos appeared and old ones became active, large earthquakes, tsunamis and stronger ocean oscillations which are caused/controlled by vulcanism/tectonic activity. In Dr. Fairbridge's hypothesis on gravity affecting the sun we can surmise that the effect would be strong enough to affect the earth as well, stirring things up, so to speak. This explains why only the northern pole is a problem and not the southern pole. It also explains the South Atlantic Magnetic Anomaly and why we had glacial melts. If you take into account all the anomalies since 1975 you start to see the pattern.
  13. Actually I should have said that the results were immediate but we did not see any symptoms for a few years. Many of the recent finds are only known to be recent but not all have a date associated.
  14. QM: I hear what you say and (as I have said in other places on this site) it simply re-inforces my view that the basic physical model still has some bits missing or not fully understood. We do not even have a reliable physical model for the fluid dynamics of the earth core, so how can you compute tectonic effects into the climate model that would have any real meaning? As an aside: The moon causes tidal waves in all earth's material phases, and that effect is constantly modulated by the sun all the other planetary bodies. I would not care to try and model that either!
  15. I came here seeking some clarification. I now have a headache. Nevertheless, thank you everyone for a thoroughly scientific and impersonal debate on this topic. Its refreshing to read a thread like this minus all the politics and high emotion that usually comes with it
  16. theTree Unfortunately some threads here are also a bit heated but it is still much better than RealClimate.
  17. Austerlitz The relationship as stated and accepted by the IPCC may indeed be false, I agree. But there is a feedback that has a minor effect and can be viewed as symptomatic. Spencer gives a good explanation for this, the sensitivity to CO2 is lower than the sensitivity of other drivers/forcings and easily overcome which is indicated in the current cooling trend. The idea that CO2 caused AGW therefore is rather meaningless since it is not strong enough to have driven climate change from 1975 through 2007. Recent articles on ocean oscillations and plate tectonics/vulcanism indicate that "The solar jerk" is at work.
  18. Apparently climatologists do not have much grounding in how feedback works. Unaware of their ignorance, they invoke net positive feedback in their GCMs. This causes the GCMs to predict significant ‘enhanced global warming’. Anyone who has the ability and interest to look at the NOAA data from Vostok Ice Cores for the last glaciation (and prior glaciations) will discover that, repeatedly, a temperature increasing trend changed to a decreasing trend with the carbon dioxide level higher than it had been when the temperature was increasing. Graphs of NOAA and other credible data, all fully sourced so they can be verified, can be seen at (The web site is controlled by Middlebury, not me.) Those who understand how feedback works will know that this temperature trend reversal is not possible with significant net positive feedback. Thus, as far as global climate is concerned and contrary to the assumption in the GCMs, significant net positive feedback from water vapor does not exist.
  19. Dan Ok, now I am confused. I thought we were discussing CO2 here. But a reduced sensitivity to GHGs in general would also explain less sensitivity to water vapor would it not?
  20. Response of the climate system depends on the combined effect of ALL feedbacks, known or not. When all are combined, the NET feedback can not be significantly positive. This is mandated by the temperature trend reversals of the last and previous glaciations. Without net positive feedback, the GCMs do not predict significant Global Warming. Other assessments from entirely different perspectives also determine that there is no significant net positive feedback. They can be seen at and
  21. #32 and #43 You each dismiss the possibility of feedbacks to CO2-induced warming, without really explaining your problem. In each case this seems to relate to the observation that during Milankovitch cycles associated with glacial-interglacial-glacial transitions, the earth's temperature drops while atmospheric CO2 levels remain high for a while. But isn't that exactly what's expected if the CO2 rise and fall is itself a feedback from the primary (Milnkovitch-induced) warming? Obviously atmospheric CO2 levels will lag behind temperature levels on both the rising and falling parts of the cycle. It's a question of relative magnitudes of forcings, and the timescales for various re-equilibration to changes in forcings. If the solar (insolation) dominates (as we consider to be the case), then it will "dominate" the effects of CO2, feedbacks and all. We could make an analogy with the day night cycle. Right now atmospheric CO2 levels are the highest they've been for many millions of years and the Earth is warming. However last night while CO2 levels were extraordinarily high (382 ppm or whatever the current value is), when the sun went down, it got a bit cooler. In fact as the air cooled last night some of the water vapour precipitated out and it rained.... Now that scenario doesn't indicate that raised atmospheric CO2 doesn't have an associated positive water vapour feedback. It clearly does (we can measure this in the real world). It just means that the insolation effect dominates the CO2 effect, feedbacks and all. The associated thing that needs to be considered is the timescale of the effects. The CO2 feedback to warming is very slow (and likewise to cooling). Once atmospheric CO2 levels are raised they stay that way for a long time. But both the warming effect of CO2 and its water vapour feedback are a consequence of an interaction with the insolation. If the insolation drops, then the greenhouse effect of the raised CO2 and water vapour will drop immediately. And a reduction in the feedbacks will follow on different timescales. The water vapour feedback will drop quickly (days to months following reduced warming resulting from reduced insolation)....the atmospheric CO2 levels will remain high for a very long time following the temperature drop and will drop much, much more slowly in response to the cooling. In fact in the cooling part of the cycle the secondary feedback on the warming cycle (water vapour following the CO2 rise) will seem to reduce much more quickly than the primary feedback (the raised atmospheric CO2). Another way of thinking about this is to recognisie the truism that the earth's equilibrium temperature will fluctuate (by internal variations of the climate system) around a level that is "set" by whatever level of greenhouse gas concentrations and insolation that happens to pertain. However the rates at which these equilibria are attained depends on the rates at which various feedbacks respond. So what might seem to be anomalous phenomena, are not unexpected at all....
  22. Re: "But isn't that exactly what's expected if the CO2 rise and fall is itself a feedback from the primary (Milnkovitch-induced) warming? " YES!!!
  23. Re: "It's a question of relative magnitudes of forcings, and the timescales for various re-equilibration to changes in forcings" YES!!!
  24. Re: "Another way of thinking about this is to recognisie the truism that the earth's equilibrium temperature will fluctuate (by internal variations of the climate system) around a level that is "set" by whatever level of greenhouse gas concentrations and insolation that happens to pertain." ASSUMPTION!!!
  25. Well that's good don't have a problem with some of the simple expectations of CO2 feedbacks as they apply under the influence of Milankovitch cycles. On the other hand it's not obvious why you consider a truism to be an assumption! It's been known since the middle of the 19th century that the earth's temperature is defined by the insolation from the sun (which gives the Earth a black body temperature near -15 oC) and the greenhouse effect arising largely from water vapour and CO2 that supplements the black body temperature by around 30 oC. That's pretty much a truism. One cannot pretend that the greenhouse effect doesn't exist! So the solar and greenhouse contributions effectively set the earth's equilibrium temperature, and stochastic and cyclical variations in the climate system (wind and ocean currents) and volcanic effects, give rise to fluctuations around the equilibrium temperature. Occasionally rather horrible impacts from extraterrestrial sources or catastrophic tectonic events generate major abrupt perturbations. But otherwise it's the sun and the greenhouse effect. ...and indeed the major independent variable with respect to the greenhouse effect is the atmnospheric CO2 (and methane somewhat, especially in the deep past) concentration, since as we all know very well, atmospheric water vapour concentrations rather passively follow the atmospheric temperature (and pressure). What did you have in mind?

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