The Vostok Ice Core: Temperature, CO2 and CH4

In their seminal paper on the Vostok Ice Core, Petit et al (1999) [1] note that CO2 lags temperature during the onset of glaciations by several thousand years but offer no explanation. They also observe that CH4 and CO2 are not perfectly aligned with each other but offer no explanation. The significance of these observations are therefore ignored. At the onset of glaciations temperature drops to glacial values before CO2 begins to fall suggesting that CO2 has little influence on temperature modulation at these times.

As discussed at the end of this post, consideration of the geochemical cycles of CO2 and CH4 in ice, permafrost, terrestrial and oceanic biospheres and in deep ocean water during freeze – thaw glacial cycles suggests that it is inevitable that CO2 and CH4 are going to correlate with temperature in a general way. This correlation shows that CO2 and CH4 are controlled by temperature and so provides no evidence for CO2 or CH4 amplifying temperature signals that are linked to orbital cycles.


Figure 1 The location of Antarctica, Vostok and other ice core locations.

The Russian Vostok Antarctic base lies 1300 km from the S pole, close to the centre of the Antarctica continent at an elevation of 3488 m.  It currently receives 2.6 mm precipitation per year. Average temperature is -55˚C and the record low is -89.2˚C which is below the freezing point of CO2. Vostok is one of the most hostile places on Earth.

There is a history of drilling various ice cores at Vostok. The main ice core, the subject of this post, was drilled in 1995. The Vostok ice core is 3310 m long and represents 422,766 years of snow accumulation. One year is therefore represented by only 7.8 mm of ice. Vostok is a cold, cold desert and the very slow ice accumulation rate introduces significant uncertainties to the data.

In addition to ice cores, Vostok is famous for the sub-glacial lake that lies beneath that has been mapped as one of the largest lakes in the world covering 14,000 sq kms. It is clearly a lot warmer under the ice than on its surface.

Figure 2 Vostok scenery

Data: Temperature, CO2 and CH4

In comparing the temperature, CO2 and CH4 signals in the Vostok ice core, it is important to understand that the temperature signal is carried by hydrogen : deuterium isotope abundance in the water that makes the ice whilst the CO2 and CH4 signals are carried by air bubbles trapped in the ice. The air bubbles trapped by ice are always deemed to be younger than the ice owing to the time lag between snow falling and it being compacted to form ice. In Vostok, the time lag between snow falling and ice trapping air varies between 2000 and 6500 years. There is therefore a substantial correction applied to bring the gas ages in alignment with the ice ages and the accuracy of this needs to be born in mind in making interpretations. Vostok data can be downloaded here.

Note that in all my charts time is passing from right to left with the “present day” to the left. The present day (year zero) is deemed to be 1995, the year that the cores were drilled. The GT4 time scale of Petit et al is used [1].

The methane concentrations in gas bubbles and temperature variations in Vostok are incredibly well aligned, especially at the terminations and return to glaciation when temperature variations are at their greatest. (Figure 3).

Figure 3 Methane and temperature variations. Note how methane and temperature are particularly strongly aligned at the terminations and during subsequent decline back to glacial conditions.

This shows that the ice age to gas age calibration is good. But does it show that methane variations of ±200 ppbV (parts per billion) are amplifying the orbital control of glaciations?

The fit of CO2 to temperature is actually not nearly so tight as for CH4. There is a persistent tendency for CO2 to lag temperature throughout and this time lag is most pronounced at the onset of each glacial cycle “where CO2 lags temperature by several thousand years” [1] (Figure 4).

Figure 4 CO2 and temperature appear well-correlated in a gross sense but there are some significant deviations. At the terminations, the alignment is as good as observed for methane. But upon descent into the following glaciation there is a time lag between CO2 and temperature of several thousand years. Petit et al [1] make the observation but fail to offer an explanation and to take the significance into account preferring to make instead unsupportable claims about CO2 and CH4 amplifying orbital forcing.

It is therefore no surprise that CO2 and CH4 show significant differences (Figure 5) with CO2 lagging CH4 in a fashion similar to the lag between CO2 and temperature.

Figure 5 CO2 lags methane in a manner similar to the lag between CO2 and temperature. This time lag requires an explanation rooted in the geochemical environments that are both emitting and sequestering these gases. Petit et al [1] devote surprisingly little space to explaining the physical processes behind the CO2 and methane variations at all.

Petit et al [1] appear to have been more eager to emphasise the similarities than to report the important differences…

The overall correlation between our CO2 and CH4 records and the Antarctic isotopic temperature is remarkable (r2 1⁄4 0:71 and 0.73 for CO2 and CH4, respectively). This high correlation indicates that CO2 and CH4 may have contributed to the glacial–interglacial changes over this entire period by amplifying the orbital forcing along with albedo, and possibly other changes.

In fact the high correlation is best explained by CO2 and CH4 both responding to temperature change as opposed to “causing it” and there is zero evidence from this data that amplification of orbital forcing has taken place, which is not to say that it has not happened.

Figure 6 provides an expanded view of the last glaciation where it can be seen quite clearly that there is a time lag of about 8,000 years between temperature falling and CO2 being pumped down. The temperature fell to glacial conditions (-6˚C) with CO2 at interglacial values (265 ppmV). Methane fell immediately with temperature but CO2 did not. This suggets that CO2 has little control over the main structure of the glacial cycle that is controlled by orbital forcing. There are similar time lags at the beginning of each glacial cycle (Figure 4). This is clearly an important and reproducible geological process or sequential combination of processes.

Figure 6 Detail of the last 150,000 years showing how CO2 lags temperature by about 8,000 years following the Eemian inter-glacial. Full glacial conditions were established with inter-glacial CO2 concentrations.


The cyclicity of the CO2 and methane needs to be interpreted in terms of flux, sources and sinks. When the concentration rises this shows that the rate of production exceeds the rate of removal and vice versa. Envisaging glacial cycles there are a multitude of processes that one can imagine influencing both CO2 and CH4 flux. For example, sea level rise and fall flooding or draining land, vegetation growth and decay, changes to soils, ice sheets and permafrost melting, changes in ocean bio-productivity, changes in ocean circulation,  in particular thermohaline circulation.

CH4 and CO2 rise together with temperature at the terminations and it is tempting to suggest that the source for these two gases is the same. This is likely to be only partly true. The most prominent source for the CH4 is likely to be melting permafrost around and beneath melting northern hemisphere ice sheets. This will also release some CO2. The ice itself also contains small amounts of both gases. The most likely source for most of the CO2 is considered to be the oceans where warming seawater can hold less CO2. It is straight forward to explain the concordant rise of CH4 and CO2 with temperature at a time of rapid warming and ice sheet melting. When the warming halts so does the rise of CO2 and CH4, but then, with greenhouse gases at a maximum things turn colder. This alone suggests that greenhouse gases play a minor role in modulating glacial temperature and climate.

So why do CH4 and CO2 not follow each other down during cooling? There is not actually a sink for CH4. It is destroyed rather in the atmosphere by reaction with sunlight and oxygen to form CO2. The residence time is rather short, about 10 years. And so once added to the atmosphere it is quickly destroyed by conversion to CO2. The rapid warming that marks the beginning of an interglacial is normally followed in short order by rapid cooling. One can imagine the permafrost gradually freezing again, resulting in a reduction of the methane flux, the rate of destruction overtakes the rate of release and the concentration falls.

The large time lag for CO2  is not so easy to explain. At the termination and during the warming phase one has to imagine poleward migration and growth of forests. I can only guess that the mass of the terrestrial biosphere increases. I don’t know what may happen to the mass of the ocean biosphere which is often more productive in cold water? I can also speculate that thermohaline circulation is established or amplified enabling the partial degassing of the deep, carbon rich ocean. It is difficult to fit these pieces together in a quantitative way but suffice to say that warming leads to an increase in atmospheric CO2. So why does cooling not draw CO2 down again immediately?

An obvious thought is that this is linked to thermal inertia of the oceans. That the land and atmosphere had cooled with the oceans lagging a few thousand years behind. A simple way to check this was to compare Vostok CO2 against the ocean temperature record as recorded by the d18O signatures of globally distributed benthic foraminifera [3] (Figure 7). There is a similar time lag in the oceans between temperature (d18O) and CO2 (Figure 7) so the thermal inertia idea does not work.

Figure 7 There is a similar time lag between CO2 from Vostok and the temperature record of benthic foraminifera in the N Atlantic [3] showing that the slow pump down of CO2 has nothing to do with the thermal inertia of the oceans.

So what may actually be going on? A few months ago Roger and I had a series of posts on Earth’s carbon cycle. We never really got to the bottom of it but in the process learned a lot and turned up much interesting data.  I made three interim conclusions 1) deep ocean water contains much more carbon than the surface, and because of this 2) the much publicised oceanic CO2 solubility pump cannot exist and 3) most CO2 is removed from the atmosphere by photosynthesis – trees on land and phytoplankton in the oceans [4]. This may help us to understand the CO2 time lag. The deep oceans contain vast amounts of carbon, the product of rotting plankton at depth, and when the oceans warm or overturn, this C can be released to the atmosphere, quickly. But the return trip is not so simple since this depends on photosynthetic rates. In short, it seems that the oceans can exhale CO2 much more easily than it can be inhaled again.

On land, the re-creation of northern hemisphere ice sheets will kill high latitude forests and cause global migration of climatic belt boundaries towards the equator. Killing forests reduces the size of the terrestrial CO2 pump whilst simultaneously adding a source of CO2 – rotting wood. This will tend to offset the oceanic biosphere’s ability to pump CO2 down during the cooling phase.


  • Over four glacial cycles CO2, CH4 and temperature display cyclical co-variation. This has been used by the climate science community as evidence for amplification of orbital forcing via greenhouse gas feedbacks.
  • I am not the first to observe that CO2 lags temperature in Vostok [2] and indeed Petit et al [1] make the observation that at the onset of glaciation CO2 lags temperature by several thousand years. But they fail to discuss this and the fairly profound implications it has.
  • Temperature and CH4 are extremely tightly correlated with no time lags. Thus, while CO2 and CH4 are correlated with temperature in a general sense, in detail their response to global geochemical cycles are different. Again Petit et al [1] make the observation but fail to discuss it.
  • At the onset of the last glaciation the time lag was 8,000 years and the world was cast into the depths of an ice age with CO2 variance evidently contributing little to the large fall in temperature.
  • The only conclusion possible from Vostok is that variations in CO2 and CH4 are both caused by global temperature change and freeze thaw cycles at high latitudes. These natural geochemical cycles makes it inevitable that CO2 and CH4 will correlate with temperature. It is therefore totally invalid to use this relationship as evidence for CO2 forcing of climate, especially since during the onset of glaciations, there is no correlation at all.


[1] J. R. Petit*, J. Jouzel†, D. Raynaud*, N. I. Barkov‡, J.-M. Barnola*, I. Basile*, M. Bender§, J. Chappellaz*, M. Davisk, G. Delaygue†, M. Delmotte*, V. M. Kotlyakov¶, M. Legrand*, V. Y. Lipenkov‡, C. Lorius*, L. Pe ́ pin*, C. Ritz*, E. Saltzmank & M. Stievenard† (1999) Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. NATURE | VOL 399 | 3 JUNE 1999 |

[2] Jo Nova: The 800 year lag – graphed

[3] Lisiecki & Raymo (2005) A Pliocene-Pleistocene stack of 57 globally distributed benthic D18O records. PALEOCEANOGRAPHY, VOL. 20, PA1003, doi:10.1029/2004PA001071

[4] Energy Matters: The Carbon Cycle: a geologist’s view

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52 Responses to The Vostok Ice Core: Temperature, CO2 and CH4

  1. Yvan Dutil says:

    Is this consistant with Shakun, J. D., Clark, P. U., He, F., Marcott, S. A., Mix, A. C., Liu, Z., … & Bard, E. (2012). Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation. Nature, 484(7392), 49-54.,%202012,%20Nature.pdf

    • Euan Mearns says:

      Yvan, thanks for the paper. I’ll have a close read later. This is what Petit et al had to say about phasing:

      The sequence of events during terminations III and IV is the same as that previously observed for terminations I and II. Vostok temperature, CO2 and CH4 increase in phase during terminations. Uncertainty in the phasing comes mainly from the sampling frequency and the ubiquitous uncertainty in gas-age/ice-age differences (which are well over ±1 kyr during glaciations and terminations). In a recent paper, Fischer et al. present a CO2 record, from Vostok core, spanning the past three glacial terminations. They conclude that CO2 concentration increases lagged Antarctic warmings by 600 ± 400 years. However, considering the large gas-age/ice-age uncertainty (1,000 years, or even more if we consider the accumulation-rate uncertainty), we feel that it is premature to infer the sign of the phase relationship between CO2 and temperature at the start of terminations. We also note that their discussion relates to early deglacial changes, not the entire transitions.

      And I agree with that for Vostok. Its simply not possible to interpret the fine detail because of ice to gas age corrections. Trying to tie together proxy records from all over the planet is fraught with difficulty. What are we supposed to make of -620±660 y ?

      It makes geological sense to me that temperature, CO2, CH4 and temperature all rise together during warming.

      The elephant in the room is the 8000 year time lag – I’m hoping that someone may point me at some papers that discusses this. I have no axe to grind about possible processes. But as far as I can tell this is real and requires an explanation.

    • Euan Mearns says:

      Yvan, I’ve read a bit more of the Shakun paper, enough to realise that this is something I probably wouldn’t attempt to do. If you look at my figure 7 you can see Vostok CO2 leading temperature in the Benthic foram stack, particularly pronounced going into the Eemain less so going into the Holocene. This is what Shakun et al are seeing. We have de-glaciation and warming of the atmosphere with the oceans warming up a few hundred years later? But post Eemian we have the oceans cooling and CO2 staying high. But a lot of this is getting into over-interpreation of the data.

      The folks who have managed to compile all this geochem data have done an amazing job. But there are serious issues with fine scale interpretation of dates. But I am away to plot CH4 v benthic temps to see what I get.

      • One of the proxies Shakun et al don’t use is the ice core record from Huascarán in Peru (latitude 9 degrees south). Here it is plotted against the Vostok record over the last 19,000 years. Huascarán temps lead Vostok temps at the beginning of the interglacial recovery and lag them at the end. I smell an age-dating problem:

    • Roger Andrews says:

      Hi Dave:

      Might also note that Euan is talking about temperature-CO2 lags during the descent into glacial periods while Shakun at al are talking about the temperature-CO2 recovery at the beginning of the last interglacial.

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  3. clivebest says:

    CO2 has allways been a slightly positive feedback to other causes of temperature change on earth. The best estimate is that CO2 levels increase/decrease at 8ppm/K. If you convert that into climate ‘forcing’ it works out at 0.2 W/m2/K which is very small. During the Eocene temperatures were warmer and CO2 levels consequently higher. Then India collided with Asia forcing up the Himalayas and Tibet plateau slowly cooling the climate. CO2 levels fell in consequnece.

    There have only been 2 cases when CO2 levels suddenly increased seemingly independent of climate.

    1) The PETM event in the early Eocene which coincided with a sudden increase in both temperature and CO2. Although what exactly hapenned is not at all clear. Either massive volcanic activity caused the CO2 surge which led to warming or something else caused the sudden warming.

    2) Anthropgenic increase in CO2 occuring now.

    • Euan Mearns says:

      Clive, I had a long series of quotes from Petit et al as part of current post but removed them in interest of brevity and stuck them all into what may become another post. Here’s what they say about GHG forcing and my opinion about what they say.

      The extension of the greenhouse-gas record shows that present- day levels of CO2 and CH4 (~360 p.p.m.v. and ~1,700 p.p.b.v., respectively) are unprecedented during the past 420 kyr.

      The overall correlation between our CO2 and CH4 records and the Antarctic isotopic temperature is remarkable (r2 1⁄4 0:71 and 0.73 for CO2 and CH4, respectively). This high correlation indicates that CO2 and CH4 may have contributed to the glacial–interglacial changes over this entire period by amplifying the orbital forcing along with albedo, and possibly other changes. We have calculated the direct radiative forcing corresponding to the CO2, CH4 and N2O changes. The largest CO2 change, which occurs between stages 10 and 9, implies a direct radiative warming of DTrad = 0.75 ˚C. Adding the effects of CH4 and N2O at this termination increases the forcing to 0.95 ˚C (here we assume that N2O varies with climate as during termination I37). This initial forcing is amplified by positive feedbacks associated with water vapour, sea ice, and possibly clouds (although in a different way for a ‘doubled CO2’ situation than for a glacial climate38). The total glacial–interglacial forcing is important (~3 Wm−2), representing 80% of that corresponding to the difference between a ‘doubled CO2’ world and modern CO2 climate. Results from various climate simulations make it reasonable to assume that greenhouse gases have, at a global scale, contributed significantly (possibly about half, that is, 2–3˚C) to the globally averaged glacial–interglacial temperature change.

      I can accept the first half of this statement which says that CO2 and CH4 MAY have contributed to the glacial cycles and that the raw forcing effect might be of the order 0.95˚C. But the rest is pure speculation incorrectly reported as fact that inflates the relatively small raw forcing into a prominent force accounting for 50% of glacial temperature cycles. The authors ignore the fact that rapid cooling follows the GHG peak, the orbital force, whatever it is, totally overwhelms any marginal effects that GHGs have. They also overlook the fact that in the descent phase to glacial conditions that CO2 remains high for thousands of years and clearly plays no role in either keeping Earth warm or in promoting cooling.

      • clivebest says:

        That’s right Euan. CO2 levels rose after the LGM from 190ppm to 280ppm . The direct increase in CO2 forcing is therefore 5.3 ln(280/190) = 2 W/m2. That should be compared to the forcing caused by a doubling of CO2 of ~3.5W/m2 and a temperature rise of 1.1C.

        CO2 plays no direct role whatsoever in the ice age cycle. However the CO2 feedback contribution to ‘warming’ the glacial/interglacial cycle is about 0.6C.

  4. Craig Crosby says:

    Years ago I noticed that a rise in CO2 level had historically been a following phenomena rather than a leading one. What caught my attention of late is that, according to the materials I have read (including the infamous Newsweek/Time article, I don’t remember which magazine but remember reading it at the time, about an impending ice age), 1) we should be entering a cooling period and are not, and 2) all of the data in the historical reports, including those above, showed the CO2 levels at below 290, and that whenever CO2 spiked at + / – 290, there was a sudden and precipitous descent into an ice age.

    Today, however, even with the recent paucity of solar activity, which historically should cause cooling, average global temperatures have either remained constant or seen increases, and the rate of CO2 level increase has been growing alarmingly.

    From everything I have read, the greater danger is not the mere release of CO2 from fossil fuel use, but rather potential release of methane from clathrates and from melting permafrost. Since the greater danger could be realized by continued wide spread fossil fuel use, it would seem prudent to reduce that in order to reduce the danger of uncontrollable forcing.

    There are other dangers, of course. for instance, de-glaciation in the northern hemisphere could result in tectonic shifts, causing volcanic eruptions, particularly of the Icelandic volcanoes. But those are remote, and undue concern about them is not indicated at the present time. What I feel we should watch for is a continued increase in rate for CO2, not a small part of which may be caused by oceanic heating, followed by sudden spikes in methane and CO2 from turnover of methane clathrate in the Arctic Ocean and permafrost melt. That would be bad.

    On the good side, we could watch for gradual reduction in CO2 levels and cooling of the atmosphere. Long term that might be bad (leads to an actual ice age), but it would be natural for the present time.

    Again, any pronouncements should be hedged to eliminate hyperbole. My observation on reports by the IPCC is that if anything they are generally and intentionally understated. We are in the midst of an experiment on our biosphere that is unprecedented, and must learn as we go. At present it seems to me that our actions remain reckless, and motivated by greed and fear. There is a difference between confirmation and “confirmation bias” that is difficult to see, especially when we so desperately want to continue our insanely profligate way of life.

    I am enjoying the materials you present. They make us think!

  5. Javier says:

    As I see it, this issue cannot be resolved. CO2 does produce forcing. CO2 levels have never been this high in the last 3 million years when temperature swings have been much bigher than in the Holocene. So we are not going to find an answer one way or the other in the 3 million years past, when CO2 forcing has never been an issue. It is unlikely that we will get it going back to 55 million years ago, since our degree of knowledge and resolution has to be even poorer.

    As you have maintained, the crucial issue then is climate sensitivity to CO2 now. As the atmospheric battle is not going that well for the proponents of overwhelming AGW, they seem to take refuge deep in the sea, below 700 m. That is going to be a tough sell. Nobody would accept the consequences of a ban on CO2 emissions to prevent a 0.05 ºC warming of the deep oceans where not even fish live.

    Besides the correlation is strong that warmer means better for humankind.

    • Yvan Dutil says:

      That last temperature data point of your graph is 1885. I wonder where we stand now.

    • Euan Mearns says:

      Great chart!

      What is the source? I’ve not seen GISP2 plotted like this before.

      Besides the correlation is strong that warmer means better for humankind.

      This is not entirely true and lies at the heart of the current climate change “debate”. The warm periods are definitely better for NW Europe. But it seems not so good for S California.

      • Javier says:

        I made it out of the following sources, Euan,
        Humlum et al. 2011
        Biraben 1979
        Korotayev et al., 2006

        This is not entirely true and lies at the heart of the current climate change “debate”. The warm periods are definitely better for NW Europe. But it seems not so good for S California.

        It is true for most of humankind. No change can be better for all humankind, but change is inevitable. There is evidence that South-Western-NorthAmerica experienced severe droughts during the 900-1200 period. In a warmer, wetter world, certain regions might be dryer, while the world general agricultural output is expected to be larger. The world population correlation with global temperature shifts is striking. In a colder, dryer world, we would have to be able to cope with more general crop failures.

        • Euan Mearns says:

          This is from the Humlum reference. I really like this. Amongst other things it shows we are not yet at the turning point of the current Bond cycle that still lies over 100 years into the future. Sceptics would do well to mark this since we are unlikely to be cast into new LIA conditions for another 300 to 500 years – which is a very good thing. The climatic pink patch that has enabled our civilisation to thrive is not about to end.

          The quiet Sun may give us 30 years of colder climate in N Europe, but not on same scale as LIA. That is of course assuming that history repeats.

        • Euan Mearns says:

          I think its true that warming will benefit the majority. Those most vulnerable to change are along the margins of the climatic belts. Where I stay in NE Scotland we are precariously close to the temperate – Arctic boundary. You only need to go up 1000 m to be in Arctic conditions. A little warming will be enormously beneficial for us, cooling quite catastrophic as experienced during the LIA. Those wanting to prevent N Scotland becoming a little warmer are quite simply bonkers.

          The tropical belt moving northwards into desert is also non-problematic and potentially beneficial. Likewise Mediterannean moving northwards into temperate may bring some water shortages and a change of agricultural practices – the southern English may have to start growing vines again, but nothing too catastrophic.

          The main problem arises with those living along the S edge of the Mediterranean belt who may see encroachment of desert from the S. This is the problem with S California. The other problem with S California is the large population with global influence. Their wishing to cast their natural fate upon the practices of humanity spells trouble for us all.

  6. Euan Mearns says:

    Energy Matters was down for a couple of hours this evening, approximately 17:15 to 19:30. The problem was not at our host “Siteground” but internet provision “upstream” from them. I’ve been noting that my internet has been really ropey for 2 days. It does seem to be working better now.

  7. Raff says:

    You say that the oceanic CO2 solubility pump “cannot exist” just because deep water is already carbon rich. But it is a circulation: cold water descending at the poles carries a high CO2 content down to depth; the corresponding upwelling also carries high CO2 content but it has been at depth for a long time and descended at a time when atmospheric levels were lower. The shower of organic matter that adds to the carbon at depth doesn’t affect that balance, so the net effect is clearly the transport of CO2 to deep water – the solubility pump.

    Given the uncertainties involved in ice (and other) cores, it seems risky to draw strong conclusions from one Antarctic core rather considering cores from both hemispheres and other evidence in the whole. It is really not known what causes glaciation events. A look at Science of Doom’s series on the subject should shake any certainty anyone has that orbital forcing is directly responsible ( All that of course has little to do with whether CO2 acts as a greenhouse gas – we know it does. How much of an effect it had in the past seems unsurprisingly to be even more difficult to know than knowing how much of an effect it will have now.

    • Graeme No.3 says:

      “CO2 acts as a greenhouse gas – we know it does.”

      As Tonto said to the Lone Ranger “what do mean we, white man?”

    • Euan Mearns says:

      Figure 4 Comparison of pH and C content of the Pacific and Atlantic Oceans [2]. The deep Pacific has much lower pH and higher carbon content than the Atlantic.

      Figure 5 Pacific Ocean pH with depth along a transect from Alaska (right) to Hawaii (left). Note different depth scales on upper and lower panels. The upwelling of low pH deep water is I believe “the far end” of the oceanic thermohaline circulation (Figure 6) [3]. Deep water upwelling such as this brings vital nutrients for plankton from the deep ocean into surface layers. Note that the source of this image is a teaching pdf that contains many great slides.

    • Euan Mearns says:

      But it is a circulation: cold water descending at the poles carries a high CO2 content down to depth

      The cold water descending in the N Atlantic has lower C content than the cold, C rich water upwelling in the N Pacific. The net effect has to be a reduction in the C content of the deep ocean. The C rich upwelling water gets munched by phytoplankton that takes the C down again. You should stop clinging to myths and question those who have created this fantasy world for you.

      It is really not known what causes glaciation events.

      Agreed. And I think that is shocking. My own view is that there is some unknown substantial variable that has a dramatic impact on the energy budget that happens to correlate with the orbital cycles. It has to be dramatic to cause glaciations to end suddenly and then to equally suddenly start again.

      All that of course has little to do with whether CO2 acts as a greenhouse gas – we know it does. How much of an effect it had in the past seems unsurprisingly to be even more difficult to know than knowing how much of an effect it will have now.


      • Yvan Dutil says:

        Well, it is pretty much known than glaciation are caused by the orbital forcing amplified by an albedo feedback. This is plenty of literature on this topic.

        • Euan Mearns says:

          Yvan, my understanding is that orbital shifts in insolation are pretty small and cannot easily explain the pretty major climatic events that take place. And if albedo was significant we should end up with a snowball Earth as more ice reflects more radiation and we snowball into a snowball. In fact, when ice is at its maximum and we should be getting colder, the opposite happens, we hit a termination that neither CO2 nor albedo is able to halt.

          I suspect ocean currents and pattern of atmospheric circulation will be a part of the story.

          • Yvan Dutil says:

            IMHO your understanding is not up to the state of the art. While low on the average, solar forcing change is large in the Arctic. If I remember well, glaciation end when the isolation get large enough the turn to overcome the albedo effect.

            I have not the time to trace the latest open source review paper on this topic however.

          • Euan Mearns says:

            I’d be thrilled if it were that simple…

            The exact cause and evolution of ice ages still remain a mystery [1]

            1) Maureen Raymo & Peter Huybers, Unlocking the mysteries of the ice ages, Nature Vol 451/17 P. 284, 2008

            Maybe its been solved since then?


            I’m putting together some light hearted posts for Christmas period, came across this map. Yvan, any ideas why that whole stretch of Europe from the UK to Moscow seems to be anomalously free of permafrost? N of 50˚

      • Raff says:

        Euan, your blog, your rules – and no, I cannot *prove* that the “CO2 solubility pump” is not a fantasy. If I felt like reading through Sabine et al, 2004, The Oceanic Sink for Anthropogenic CO2 ( or its 20+ references I’m sure I’d learn a lot. And if I could pay for Volk & Hoffert, 1985, Ocean Carbon Pumps: … ( I’d surely learn some more about carbon pumps. But I imagine you have already studied the literature and taken current knowledge into account before deciding that the “CO2 solubility pump” is a “myth”, so I would probably be wasting my time.

        • Euan Mearns says:

          Raff, you need to shake off the persecuted complex. It just took me 10 seconds to approve this comment. I don’t have ready access to all literature but can get any paper I want to read. I don’t need to read papers on the solubility pump because I know from basic chemistry that diffusion works from high to low concentrations (Im sure there is someone out there waiting to call me wrong). A lot of papers will have been written before the oceanic C profile data were acquired. Virtually 100% of CO2 enters the oceans via solubility. But sequestration occurs via photosynthesis and gravity. I think in shallow shelf seas where lime stones are formed a different process may operate, but I have been discussing the oceanic process here.

          PS why don’t you vote on Roger’s CC thread?

  8. Graeme No.3 says:

    All these posts assume that the figures for CO2 are correct.
    If they are then it is difficult to see that CO2 controls the temperature of the Earth.
    Firstly, does CO2 precede warming? Doubtful if the source is the oceans, which would have to warm first.
    Secondly, the previous 3 interglacials were all warmer than today with lower CO2.
    Thirdly, the failure of ‘high’ CO2 to maintain temperature. (a reverse situation to No.1)
    Fourthly, even the Holocene Optimum occurred with lower CO2 levels; or so we are told from the ice analysis, but evidence from stomata counts suggests a much more variable (and higher) CO2 level in the Holocene.

    I note Clive Best’s comment on the PETM event, but we don’t know what caused it, and as for Anthroprogenic increase in CO2 occuring now, what temperature increase? If we compare events within the current interglacial, there are several times of higher temperatures than today. Does he postulate release of CO2 causing warming delayed by centuries (consistent with Shakun, but not with the IPCC)? Even if that was true, surely a benefit for mankind when the next ice age arrives (if we knew what causes them).

    • Euan Mearns says:

      Figure 9 From Clive Best [3]. On this chart cold is up and warm is down, the present day is to the left. In black is the remarkable LR04 d18O record. Hence this chart shows long term cooling and increasing amplitude of glacial oscillation. In blue are variations in insolation due to orbital parameters. From 5.3 million years to 900,000 years ago, the 100,000 year oscillation is all but absent in the LR04 data which oscillates solely in response to the 41,000 year obliquity cycle. But since 900,000 years ago the 100,000 year cycle kicks in together with the 41,000 year cycle.

      I did a post a while back looking into the timing of the next Ice Age based mainly on Clive’s work. In Europe we should be more concerned about a Little Ice Age style event. The oceanic record from LR04 d18O is truly remarkable. Earth has been getting steadily colder for 3 million years, there have been around 50 glacial cycles and a marked shift from 41,000 to 100,000 years 900,000 years ago.

      • Javier says:

        From a pure cycles and trends perspective, there is nothing puzzling about what is going on, even if one doesn’t know the actual drivers.

        There is a 150 million years cycle, with minimum temperatures at 150, 300 and 450 Mya. So now we are getting to a minimum that explains all the cooling for the last 90 My.

        Another 30 My cycle explains the Cretaceous Hothouse 80 Mya (a maximum for both 150 My and 30 My cycles), the Paleocene-Eocene Thermal Maximum 50 Mya and the Antarctica Melting 20 Mya. We should be getting to a minimum of this cycle in 10 My. give or take.

        Those two cycles appear set in stone and define the general trend that up to now has been cooling with the moving average set below ours at -2 ºC anomaly.

        As the 150 My cycle starts to turn up while the 30 My cycle is still pointing down, we get conflicting forces that manifest at maxima and minima as increased instability, and hence the PETM event 50 Mya and the kick-in of the 100 Ky cycle about 1 Mya.

        Whatever the feedback phenomena that pushes the temperatures away from the moving average will soon start facing an increasingly stronger mean-reverting force that eventually overcomes the phenomena and in taking the temperatures back to the mean, overshoots going over to the other side pushed by the opposite feedback phenomena. This is trivial and everyday experience in stock markets, and the essence of the appearance of cycles.

        One does not need to know anything about climatology to understand what is going on, only a good record of past temperatures. The corollary is that whatever efforts we make to take our temperature away from the mean are going to be increasingly difficult and “short” lived.

        Most likely neither of us is going to be alive when the temperatures start running towards the mean, but whoever is alive is not going to like it.

    • clivebest says:

      There is another effect which we overlook and that is the precession of the equinoxes. The earth’s orbit is elliptical and perihelion (closest approach to sun) currently occurs in Northern hemisphere winter – Jan 3rd. The onset of the current interglacial coincided with perihelion in Northern hemisphere summer leading to melt back of the ice sheets.

      Conditions are now really set for a new glaciation to start. Luckily the eccentricity of the orbit is lower on a 400,000 year cycle so it is touch and go when the new ice age will begin. You can estimate when based on the similar interglacial 400,000 years ago. The earth really should begin cooling within about 1500 years.

      Enhanced CO2 levels thanks to burning fossil fuels could be a blessing in disguise because this will likely offset the next ice age by several thousand years.

      Perhaps Lord Stern can redo his cost/benefit analysis to include the risk of a new ice age. If he factored that into his climate economics then he might reach a very different conclusion.

      The GDP of North America, Russia and Europe would fall to zero!

  9. Graeme No.3 says:

    If I understand the solar astronomers, the sun has completed a burst of activity not seen since roughly 8,000 years ago. This coincides with the 2 civilisations in the Sahara when it was wet and green, backed up by the Tassili frescoes. Archaeologists indicate there was an absence of population for some time followed by a different culture. This absence seemed to correlate with a dip in solar activity, before recovery, and warmer temperatures.
    The sun is classified as a variable star and we are assured that similar stars can vary in output by 4%. A drop of that size from the present would be catastrophic for humans, and even if this variation is too extreme, a 1-2% change linked with orbital variation would be enough to explain a descent into or climb out of an ice age. That is speculative and seems unlikely. We may be facing either a Dalton or a Maunder minimum. I would point out that the latter was preceded by roughly 300 years of fluctuating but usually cooler times than the 300 of the Medieval Warm Period.

    O/T but re Figure 9 and increasing amplitude of glacial oscillation, that would seem to be an unstable oscillation which could suddenly switch to a stable state. We humans can only hope that it chooses the warm state.

  10. Hello Guys,

    a lot of nice graphs and alternative intepretations. I believe you all will have an easy time to explain/simplify/ignore the continuing warming trend and the *fact*, that 2014 is almost certainly going to get the hottest year in the instrumental record. I would not bet too much money however, that 2015 will be another record-breaker anyway…:



    • Euan Mearns says:

      Global sea ice anomaly is slightly positive. And the temperature view from Space certainly won’t hit a new annualised record this year, so I imagine there will be a lot arguing about which data to use. Any phenomenon like this if it is not clear from all the data, then it is not clear. But CO2 is up and there should be some warming as a result. Depends on how you package the message. “Earth’s temperature about to soar” – shut down the FF industries and civilisation and lets kill off a few billion in the process. Or do we take a different approach?

    • Javier says:

      That’s an easy one Alex,

      Within a general warming trend that is taking us away from the Little Ice Age minimum around 1750, there appears to be an about 65 year temperature cycle. Recent up legs of the cycle have been 1910-45 and 1975-2005, while the last leg down was 1945-75.

      We are now sitting on a maximum about to start a leg down. The consequences of being on a maximum are two: Maximal temperatures and decreased rate of warming. We are observing both.

      Nothing to lose sleep about. The next leg up won’t be coming until about 2040. Until then the warmalarmists are going to have a rough time unless they get us to reduce emissions and claim victory.

  11. John Reid says:

    Hi Euan, this is my first post. I am a physicist with a background in statistics and spectral analysis. I have long been interested in climate “cycles” and I have come to the conclusion that, for the most part, we are actually dealing with red or pink noise. This is particularly true of the 100,000 year eccentricity “cycle”. I am rather sceptical about Javier’s 150 million year cycle but I have not looked into it in detail. I believe the ice age cycles are band-limited red noise with small coherent signals at the obliquity and precession frequencies. These signals only account for a small proportion of the total variance.

    See my (new this week) blog and the pages “Pause for Thought” and”Bounded Random Walk”.

    • Euan Mearns says:

      There is little disagreement among scientists that the four cycles seen at Vostok have origins in Earth’s orbit around The Sun. The “100,000” year cycle reflects the eccentricity of Earth’s orbit and explains 37% of the power spectrum. It is also evident that there is considerable variation in the duration of this cycle and its interaction with others. Cycle 1 lasted at least 128,357 years while cycle 3 lasted only 84,663 years. Superimposed upon the eccentricity cycle is the obliquity cycle of 41,000 years with 23% of the power spectrum and the precessional cycle of 19,000 to 23,000 years has 11% of the power spectrum.

      • Hi Euan:

        I may have reinvented the wheel, but here’s something else to throw into the mix.

        There was more ice accumulation during interglacials than during glacial periods.


        • Euan Mearns says:

          Yes Roger, I think you may have re-invented the wheel. I looked into this years ago upon noticing a strong correlation between snow accumulation rate and temperature. I sent that off to Petit who did reply saying something like temperature is used in the snow accumulation rate model and so they auto correlate

        • temperature is used in the snow accumulation rate model and so they auto correlate

          Lurking in the back of my mind is the suspicion that there’s something fundamentally wrong with the way ice core records are processed. This is an example. A “model” that shows more snow accumulation during interglacials when ice sheets are retreating than during glacials when ice sheets are advancing is counterintuitive. It’s also the exact opposite of what we see in the high-resolution Quelccaya ice core record, where the LIA is clearly defined by a decrease in temperature and an increase in snow accumulation rate.

        • Euan Mearns says:

          This chart I made in 2009. Old, old version of XL, my annotation has dropped off!

      • John Reid says:

        If you plot the delta T spectrum using the unfiltered periodogram on log-log scales and showing chi-squared confidence limits it becomes apparent that the apparently strong peak at 10^-5 yr^-1 is not really significant. What is significant is the whitening at lower frequencies. I used a coin tossing experiment to demonstrate that this peak and the whitening can be attributed to a bounded random walk process. See

        The same whitening at low frequencies can be seen in the Fig. 1 of Pelletier (2002) PNAS 99 suppl 1 2546-2553

        (How can I show a jpg of Pelletier’s graph here?)

        • clivebest says:

          Why would the same random walk repeat itself for the last 900,000 years ?

          • John Reid says:

            It hasn’t. Only the coherent signals at 40,000 years and 23,000 years have repeated themselves and even then, not precisely. Until 450,000 years ago terminations were 40,000 years apart, then 80,000 years apart and last two were 120,000 years apart. It appears that the climate system is loosely coupled to a subharmonic of the obliquity frequency. How much of the variance do these two components account for? I had an idea it was a fairly small proportion.

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