Guest essay by Euan Mearns
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.
Introduction
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.
Discussion
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.
Conclusions
- 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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Beautiful clarity in your work, Euan. Thanks very much.
Just one question – as I’m not familiar with the methodology of the Petit et al work :
The correlation produced for CH4/CO2 and temperature determines the calculation of the lag – is that so?
If so, then the assumption is made that the trapped air bubbles have a complement of CH4 and CO2 that is not modified during the long compaction process, or we could end up with different lag errors for the different gases. What is your take on this? Am I just being difficult? It would throw a different light on the conclusions if the lag(s) were questioned.
Looks like Robert of Texas (above) was on about the same thing and I didn’t really notice. Sorry. But maybe others have some useful comments on this?
Figure 5 (above) is probably the most important here. This is also dealt with in another comment. The time to make ice at Vostok is several thousand years. So there is plenty time for exchange between firn and atmosphere and for diffusion within firn before bubble closure. All I have to go on is the observation that CO2 and CH4 are quite closely aligned at terminations but not so on return to glaciation. The diffusion characteristics of CO2 and CH4 may well vary, but I don’t think this explains the 8000 year time lag.
The intermediate 800-yr lag puts the MWP as the precursor of the current CO2 rise. Note that the Mona Loa records show no fluctuations corresponding to known variations in human emissions.
Brian, the lag of CO2 after a temperature change between the MWP and LIA is only 50 years at the onset of the LIA and the change in CO2 is only ~6 ppmv for a temperature change of ~0.8°C. As the MWP is about as warm (if not warmer) as today, the change of CO2 caused by the temperature increase since the LIA is not more than 6 ppmv. The rest of the 110 ppmv increase is from human emissions. See the Law Dome ice core:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/law_dome_1000yr.jpg
from Etheridge e.a. 1996.
The overall change over the 8 glacial – interglacial transitions and back is about 8 ppmv/°C, mainly caused by the deep oceans (as the change in δ13C is small). The current increase needs at least 12°C temperature increase of the ocean surface to have the same effect…
Wrong way round. It’s the onset of the MWP that drives current CO2 rises.
The recent Royal Society and NAS report also states at point 20 that if we stopped all human co2 emissions today it would take thousands of years before co2 levels or temp changed. Rather a different story than some of the scientists and MSM are telling the public.
https://royalsociety.org/policy/projects/climate-evidence-causes/question-20/
If you accept as a starting point that rise in CO2 is down to burning FF then you quickly conclude that about 50% of CO2 emissions are removed from the atmosphere each year. It’s actually quite miraculous. Our tentative conclusions are CO2 fertilisation and biosphere expansion are the processes. How long this can go on? One thing for sure, burning forests in power stations instead of coal is probably the worst thing you can do.
Switch off emissions today and the photosynthetic terrestrial and ocean pumps continue to pump and we should return to substantially reduced levels of CO2 within a couple of centuries. Apollo astronaut Phil Chapman blogs on Energy Matters and described an equilibrium distribution theory that I think may be correct. Burning FF has changed the amount of C circulating in the atmosphere and biosphere, so we don’t pump down to pre-industrial, but a shifted baseline. But with climate sensitivity likely less than 1.5 that doesn’t really matter.
Switch off emissions today…and all processes dependent on CO2 will reduce it to limiting again….back to where we were
Biodeposition of carbonates as minerals has a much longer timescale than we’re used to, but ends with starved plants and their consumers. Gaia wants us to recharge the air with some of that lost plant food.
>:)
The recent Royal Society and NAS report also states at point 20 that if we stopped all human co2 emissions today it would take thousands of years before co2 levels or temp changed.
That is not what the Royal Soc report says, it says: “if emissions of greenhouse gases were to suddenly stop, Earth’s surface temperature would not cool and return to the level in the pre-industrial era for thousands of years.” Not the same thing at all.
Same thing Phil.
Assumed CO2. How else do temps stay .5° higher when natural variation does that in half a century.
All alarmist BS, Phil. Do not let them frighten you.
Neville, the slow reduction of the extra CO2 in the atmosphere is based on the Bern model, which assumes a saturation of the deep oceans, for which is not the slightest sign. The current sink rate is directly in ratio to the CO2 pressure difference (pCO2) between atmosphere and the ocean surface, the latter slightly depends of the surface temperature. That gives an e-decay rate of about 50 years or a half life time of ~40 years, not much different from a similar calculation made by Peter Dietze some 17 years ago:
http://www.john-daly.com/carbon.htm
That shows that the deep oceans still don’t show any sign of saturation…
Concerning orbital (Milankovitch) cycles inducing the glacial cycles. It is well known that changing orbits vary the solar irradiance at Earth. But the main effect alternates between northern and southern hemispheres. So when the NH is in glaciation, the SH is receiving extra irradiance on the 22 kyr cycle. Yet the NH gets heavily glaciated, the SH not. This must indicate a strong dependence on the greater ocean surface in the SH moving heat around, and possibly on changing cloud cover. The colder NH possibly turns off the AMO, chilling the Arctic even more, and this is further amplified by higher albedo.
I wish I new the answer 😉 I think thermohaline circulation / Gulf Stream is critical to the presence or absence of ice in NW Europe. My thinking goes: Sun – spectral output – thermal structure of atmosphere – sub polar jet stream – atmospheric circulation – ocean currents – large scale heat transfer to high latitudes.
I have been a fan of Bond et al 2001 (science) for many years but I’m finding hard to validate their data. They advocate competition between Labrador Current and Gulf Stream.
Linking any of this to Milankovitch is a bitch.
To Euan: One factor that we KNOW changes Earth’s energy input is the orbital cycles. So we are obligated to work them into the mix. I agree they are not the whole story, but likely are what begins the cycles.
To tty below: I agree that the NH has much available land to collect ice, whereas the SH does not. Even if Antarctica rew more ice, that would chamge albedo very little. Another likely factor is that the NH has restricted ocean current circulation, whereas circulation in the SH is wide open, and includes the circum-Antarctic current.
Donb:
The circum-antarctic current (and associated weather, which is cold, wet and stormy) will, if anything, promote glaciation if there were only some land for it to occur on. Nearly all the Subantarctic islands have been, or still are heavily or completely glaciated and the same is true for the only two major landmasses that really stick down into the stormy belt (Patagonia, South Island).
The reason there is not much glaciation in the South is mostly due to there being no place for much more ice than is already there. It is impossible for an ice cap to expand beyond the 500 meter isobath, because a glacier front can’t become higher than c. 50 meters because of mechanical strength constrainta. This means that the Antarctic ice cap cannot grow very much during glaciations, no matter how cold it becomes. It does grow a bit because NH glaciation lowers the sea-level, but it never becomes more than about 30% larger in volume than it is today.
Outside Antarctica there were substantial icecaps over southern South America and the South Island of New Zealand,, but there are no other land areas of any size at reasonably high latitudes (and with reasonable precipitation). Australia is too low, too far north and too dry for major glaciers (except for Tasmania), and the same applies even more to South Africa (though there are traces of small-scale glaciation in Lesotho, so if future glaciation gets just a little colder….).
Euan,
This may be of interest as well:
“In this work ice-core CO2 time evolution in the period going from 20 to 60 kyr BP [15] has been qualitatively compared to our temperature cycles, according to the class they belong to. It can be observed in Fig. 6 that class A cycles are completely unrelated to changes in CO2 concentration. We have observed some correlation between B and C cycles and CO2 concentration, but of the opposite sign to the one expected: maxima in atmospheric CO2 concentration tend to correspond to the middle part or the end the cooling period. The role of CO2 in the oscillation phenomena seems to be more related to extend the duration of the cooling phase than to trigger warming. This could explain why cycles no coincident in time with maxima of CO2 (A cycles) rapidly decay back to the cold state.”
http://einstein.iec.cat/jellebot/documents/articles/Phis.Lett.A_2007.pdf
We have observed some correlation between B and C cycles and CO2 concentration, but of the opposite sign to the one expected:
==========
which is consistent with the graphs. if CO2 has an effect on temperature the sign is opposite to what climate science believes. More CO2 causes cooling.
Last sentence of first paragraph brought my first question:
“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.”
When does CO2 have real influence on temperature modulation? When has it had such influence?
“with greenhouse gases at a maximum things turn colder” says it all.
That’s always been my take on the ice core graphs, why, if the GH gases are a strong ‘forcing’, do we re-glaciate when they are at their highest levels.
We re-glaciate when oceans are warm and the polar sea ice is thawed. This polar ice cycle does not really care what the GH gases are doing. Look at actual data.
I have trouble believing we can use air bubbles to give us any meaningful level of accuracy for any of these variables.
Randy, having read up a fair bit on ice core interpretation, let me qualify your doubt (butnonly as a self educated layman on the subject). It is not as bad as you might think.
There are two problems. First, when did the bubble form as firn converts to ice. That depends on a lot of things. So lends an estimable amount of temporal uncertainty to the bubble. Second, sunsequent diffusion from the bubble into the ice. The further back in time, the more this can distort results. So uncertainty increases with age. But careful ice core analyses bound these issues. Euan’s post carefully stays in territory outside those uncertainty bounds, that is on pretty solid ground.
Rud,
I agree with your comments, but add some extra.
Diffusion of CO2 is driven by both pressure and concentration gradients between the bubble and outside. As the bubble is squeezed and pressure grows, air inside diffuses outward. But CO2 concentrations are measured relative to N2 which also diffuses outward. So in principle this process should not change the relative CO2 concentration. CO2 diffusion driven by concentration moves both ways, into the bubble and out. This is presumably why the relative CO2 concentration reflects changes in the atmosphere, or at least CO2 in firn above. So long as the bubble remains in diffusion communication wit the atmosphere, it tends to represent changes in air CO2.
BUT there are minor factors which are harder to predict. CO2 and N2 likely differ in the degree they are “sticky” inside the bubble due to physical or chemical absorption. Such may fractionate CO2 from N2. Also, at very low temperature the diffusion rate is slow, and will cause some lag time in response to concentration gradients. These effects are hard to evaluate.
Rud, there was some theoretical estimate of CO2 migration in relative “warm” coastal ice cores, based on migration near remelt layers in the Siple Dom ice core. That translates to a broadening of the resolution from 20 to 22 years at middle depth and to 40 years at near bedrock. Not a problem. See:
http://catalogue.nla.gov.au/Record/3773250
In the much colder inland cores (Vostok, Dome C) there is no measurable migration, as if there was any migration, the CO2/T ratio over the interglacials/glacials would fade for CO2 for each interglacial 100 kyear back in time…
It’s the-nothing-is-what-it-seems magic show.
If you zoom in on the last glacial transition (<20ka), you'd see that the CH4 corrolates strongly (instantaneous) with the Greenland ice core isotope thermometer, while the CO2 corrolates (lagging) with the Antarctic ice core isotope thermometers, while there is a clear significant difference between the two groups, http://img38.imageshack.us/img38/9509/transitioniceagegrlndan.png
Yet, both gasses are global in nature. So what was the global temperature doing?
But then again CO2 from ice cores seem to underestimate CO2 compared to quickly increasing and -apparantly robust stomata record ie Steinthorsdottir et al 2014 QSR 99 -pp 84-96, while the isotope paleothermometer may be considered suspect at best (. https://dl.dropboxusercontent.com/u/22026080/non-calor-sed-umor.pdf ).
Maybe we should start from scratch again interpretating the geological records.
The isotope paleothermometer may be suspect but anyone who thinks the Younger Dryas wasn’t cold in Northern Europe is simply ignorant. Says one who grew up literally on the end-moraines left by the Younger Dryas. Don’t tell me that those moraines, and sandur fields, and nivation niches, and niche glaciers, and frost wedges, and patterned ground, and fossil pingos were caused by warm climate.
Sure, but you checked the time scale. If anything was cold, why not the Allerod, shortly before the Younger Dryas?
http://www.sciencedirect.com/science/article/pii/S0277379107001035
Because Alleröd, in contrast to Younger Dryas was a time when the inland ice retreated, sea-level rose and animals and plants (including humans) dispersed northwards and colonized the newly deglaciated areas.
André, ice cores don’t underestimate CO2, CO2 levels at closing depth are the same in the newly formed ice bubbles as in the still open pores. There mat be some migration, but that only broadens the resolution and can’t change the average over the time of resolution. Stomata data are far from robust and while they have a better resolution (of local CO2 changes over land, not necessary in the bulk of the atmosphere), if they show higher CO2 levels over the resolution period of the ice cores, they are certainly wrong…
One thing notable in the entire ice core record is that there never was a time where the concentration of CO2 came anywhere near 400 ppm. In other words, irrespective of any lead-lag relationships, we currently are in uncharted territory.
The evolution of C4 photosynthesis….
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2004.00974.x/pdf
That study does not say how the C4 pathway affects climate.
David, you have it backwards…..
It should be: “there never was a long time where the concentration of CO2 came anywhere near 400 ppm.”
Ice core records are notoriously unable to resolve brief event. Actually stomata studies suggest that CO2 levels did touch 400 ppm briefly during the last deglaciation. Rather worryingly it happened just before temperatures plunged at the beginning of the YD.
Per the article “One year is therefore represented by only 7.8 mm ”
…
Therefore 50 years would be over 15 inches.
…
You would surely see a “blip” in CO2 concentrations in a 15 inch long core. There aren’t a whole heck of a lot of stomata in the Antarctic. You won’t find 400 ppm of CO2 in any of the Greenland ice cores either.
Actually stomata studies suggest that CO2 levels did touch 400 ppm briefly during the last deglaciation. Rather worryingly it happened just before temperatures plunged at the beginning of the YD.
=============
consistent with the graphs. if increased CO2 has any effect on temperature, it is increased cooling not warming.
David Socrates:
Remember that the gasses aren’t isolated until the pressure is high enough to compress the snow into solid ice. That happens at a depth of about 300 feet. To accumulate that much snow takes millenia in inland Antarctica and centuries in coastal Antarctica and Greenland.
The gasses in a single bubble is a mixture of atmospheric gasses from this whole interval, though of course in lesser proportions from the later part.
The recent WAIS Divide ice-core (from a high precipitation site) has better resolution than earlier cores and can apparently just barely resolve century-scale events in the Late Pleistocene. Not unexpectedly it is much “bumpier” than earlier ice-core records, but still very smeared-out compared to stomata measurements.
tty:
I don’t know how much to trust stomata data. Plant stomata serve mainly to intake CO2 into the leaf for photosynthesis. But H2O also escapes through stomata, and this may be deleterious for the plant. If the plant has ample water, then CO2 alone may control stomata size and number. But if water is limited, the plant may lessen the size and number of stomata to prevent H2O loss (and limit its growth rate), even when CO2 is plentiful.
tty, the resolution of ice cores depends of the local snow accumulation rate at the place of the core. That is very high at coastal cores (Law Dome, Siple Dome) and very low for inland cores (Vostok, Dome C). The resolution is less than 10 years for Law Dome, but the 1.2 meter ice equivalent makes that rock bottom was reached for 150 years of ice only. For Vostok, the resolution is 600 years and for Dome C 560 years but go back in time for 420 resp. 800 kyears.
As for any ice core the reproducibility of CO2 measurements is about 1.2 ppmv (1 sigma), that gives that the current increase of 110 ppmv over 160 years would be visible in all ice cores, even Vostok and Dome C, as a peak of at least 15 ppmv and more for the better resolution ice cores.
Forget stomata data, they show local CO2 levels over land which may go all over the scale, depending of what happens in the main wind direction (land use changes, type of crops,…). Taylor Dome has a resolution of ~40 years and spans the LGM-current deglaciation. There is no peak of 400 ppmv visible…
Latitude, you point about the C4 pathway evolution is irrelevant to the discussion of CO2 in ice cores.
David Socrates
December 27, 2014 at 2:30 pm
One thing notable in the entire ice core record is that there never was a time where the concentration of CO2 came anywhere near 400 ppm. In other words, irrespective of any lead-lag relationships, we currently are in uncharted territory.
==========
David, if you don’t have an ice core that goes back prior to C4’s……then you only have ice cores when CO2 was limiting
No this is not correct. From geology point of view we currently live on the CO2 starved planet. Most of the time co2 level was much higher. Stromatolites that existed since the Archean are intertidal bacteria endured co2 of more 10% in the atmosphere.
Dariusz
…
From an evolutionary point of view plants have adapted to the levels of CO2.
Yes, plants have adapted to the present starvation levels of. They prefer much higher levels of CO2. That’s why greenhouse growers jack up the CO2: it is harmless, and it is very beneficial.
Of course, that deconstructs the entire alarmist narrative. So as Richard Courtney writes above:
dbstealey is correct and you are wrong…
There is no one who is less inclined to face facts than D. Socrates. Because if he did, he would be forced to admit that skeptics have been right all along: CO2 is harmless and it is beneficial to the biosphere. More is better.
But some folks just cannot admit that anyone else is right. They would rather die first. Remember: Martyrs will die to be right. But that doesn’t mean they are. All it means is they are too unreasonable and too stubborn to accept reality.
“““Yes, those of us up to speed on the subject know that global temperature (T) rises or falls the most at night”
….
Boy, I’m glad I’m not up to speed like you are.
….
http://wattsupwiththat.com/2014/12/31/2014-in-review/#comment-1825830
Sock rats:
What’s the matter? Did you run out of junk science? Nothing left but sneers?
Something tells me this is the real sock rats.
Mpainter…….payback for all the name calling dbstealey does.
…
Besides, I’m just pointing out how “up to speed” he is.
I did hear a speaker address this. He said that the gases do migrate in these ice cores. They are not in a crystalline lattice. So, you would expect CO2 in areas of higher concentration to migrate to areas in the ice of lower concentration. He concluded that the concentration of CO2 was certainly higher than the values found in the ice cores today.
I don’t know if any of this is true or accepted by other climatologists. But, it makes sense.
If you google “diffusion of CO2 in ice” you’ll get several pdf’s that address the topic. The short answer is yes, but not a lot.
http://popesclimatetheory.com/page16.html
This tiny bit of CO2 in uncharted territory is still a tiny bit and cannot regulate the temperature of Earth.
Go find something abundant, such as water in all of its states.
http://popesclimatetheory.com/page76.html
That first link is p, at best, irrelevant, if not juvenile. If one of ten thousand is insignificant according to you, then at what point is it significant and why. Is this a molecular democracy?
“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.”
I don’t think you can be correct that such a freezing is going to cause wood to rot. There is driftwood on the north shore of Greenland that had to have been beached during a warmer period, maybe even the Holocene Optimum. Rotting suggests abundant bacteria and moisture and I believe it was a pretty dry cold desert we are talking about here.
Dead forests burn well, even when it’s cold. Ever try to find any remaining wood from the previous interglacial?
“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.”
It may be “invalid to use this relationship as evidence for CO2 forcing of climate” but I assume you don’t mean to suggest the opposite, that CO2 forcing isn’t happening now. Just checking.
Exactly why CO2 lags temp in the distant past is still an unanswered question, which is why Petit et al don’t speculate as to the cause. That strengthens the paper in my opinion.
And it is also unwarranted to suggest that CO2 forcing is happening at a level that is appreciable to hyper ventilate. Requires a much more precise estimate I’d sensitivity. Which we do not have.
It’s the expansion and contraction of the solar system and it’s effect on the sun, two major players in actual climate fluctuations, I’m just letting you know. and yes there are observations on this spanning hundreds of years!
About the CO2 lag to temperature at glacial inception. Ryan mentions die-off of taiga forests. I can think of one more process that would have similar effect in decreasing CO2 uptake and increasing supply. Sea levels would fall rapidly so that the shallow seas with high primary plankton productivity would be drained and become exposed mud. They would rot and stink for a while before eventually becoming covered in terrestrial vegetation.
iPhone spellcheck changed Euan to “Ryan “.
I meant Euan.
CO2 lags behind the temperature changes. Simple as that. And they are sometimes going in opposite directions as well.
The ice ages start when the snow and sea ice does not melt-out in the summer at 75N. Summer solar insolation needs to drop below 420 W/m2 at 75N for this to happen. Today it is about 450 W/m2 and the sea ice and snow melts out with a few months to spare. The solar insolation at 75N will not decline to the 420 W/m2 level until either 52,000 years from now or, more likely, 125,000 years from now. No ice age for a long, long time.
Once the glaciers start building up at 75N, they gradually start to reflect more and more sunlight and they start pushing south, reflecting ever more sunlight. It is only until the summer solar insolation stays high enough, for a long enough period of time, say 5,000 years that enough 2 km thick glacier can be melted back starting at Chicago and ending at Eureka at 80N, before an ice age comes to end. It takes time to melt all that ice out. If the Milankovitch Cycle spikes up for 3,000 or 4,000 years, that is not enough time to melt out the ice and the ice age goes on and on. It is more-or-less just a fluke that in the last 800,000 years, the upspike ending the ice ages come at 100,000 years apart. They are not regular.
It is snow melting at 75N or not and then at least 5,000 years of upswing to melt out the glaciers.
Notice there is no role for CO2 in that physical explanation.
I strongly doubt those 50 000 / 125 000 year interglacial theoiries. It seems extremely unlikely that we just happen to be living in the longest warm period for at least 15 million years (yes, it was as warm or warmer during parts of the early Pliocene, but there were no uninterrupted warm periods nearly that long). The whole thing reeks of “the anthropic principle”. It seems much more likely that there is some unknown factor we haven’t figured out yet that prevents the occurrence of very long warm intervals. After all it isn’t as if we really understand why glacials are about 100 000 years long, so I don’t really have much confidence that we can predict the length of an interglacial.
The important orbital cycles for glaciation are about 22 kyr and about 100 kyr in length (see Euan’s graph). We are entering a time when these two cycles tend to cancel out, and so any cooling in the next 50-100 kyr will be less than prior.
Back before the ~100 kyr glacial cycles began about a million years ago, glacial cycles were less intense and on ~44 kyr cycles (another orbital cycle). It is unknown why the change-over. Global temperature began dropping about 5 million yrs ago. That was likely due (at least in part) to changes in ocean circulation and land mass distribution, especially the closing of the ocean connection between South America and Central America.
@tty
December 27, 2014 at 3:49 pm
tty, you see the peaks of warming in the graphs above do show at least the last three Interglacials, acoording to the data and the interpretaition of the glacial and interglacial cycles. There the interglacials seem to be as 15k years long and the glacial periods at about 100K years long.
But that is according to the polar regions temps.
What shown by the data is that actually the chance of the interglacials to be 15K years long is a good enough one, BUT NOT THE SAME CHANCE FOR THE LENGTH OF THE GLACIAL PERIODS.
So the accuracy of the polar regions temps showing an interglacial and it’s correct length could be explained by the coincidence that the orbital forcing minima (once every 100K years) coinciding with an interglacial period, meaning that there inbetween could be other interglacials inbetween but the signal will be weaker in the polar regions temp data and in accordance the whole period between such clearly defined interglacials will be considered a glacial period.
The Ice core data in their own can not be showing an accurate picture of the global climate, but more so for the regional polar climate.
The most and the only accurate thing that Ice cores data can show about the climate is the length of what called interglacials, and that so only because of a coincidence of the interglacials periodicity and the orbital forcing minima, meaning a stronger signal for only these “lucky” interglacials in the Ice cores, while the “unlucky” ones missed and considered as glacial periods..
cheers
In today’s world, there is almost no land at all north of 75 N latitude. Are you sure of this latitude? Even the north coast of the Siberian and Canadian arctic is between 70 – 72 north. Sea ice? Yes. But glaciers? No.
Ellesmere Island, northern Greenland, generally non-glaciated right now, the Arctic sea ice which melt out in the summer is at 75N.
Even in the deepest downturns of the Milankovitch, the summer sun is more than strong enough to melt out the snow at 65N in the summer The sea ice always melts out at 65N in the summer.
75N is the make-or-break latitude where the ice ages start.
It’s not just a matter of latitude. Altitude and precipitation are extremely important too. The mountains of Scandinavia was a core area for previous glaciations and they are between c. 60 and 70 degrees north (we know that the ice reached the coast near Bergen even during the very first cold snap of the latest glaciation, MIS 5d) .
On the other hand Eastern Siberia and Alaska and Yukon north of the coastal mountains have never been glaciated – too dry.
the Iceage correlation is with insolation at 65ºN.
Just a chart showing the Milankovitch Cycles versus the last Four Ice Ages. To say it is complicated is an huge understatement.
It takes a really good down-turn to kick us out of an interglacial into an ice age and then it takes a long time to melt out all that ice and overcome its thermal inertia. One should also keep in mind that at the southern edges of the ice-sheets (as in Chicago), the summer sun is almost the same as today and the ice-fronts are melting rapidly in the summer at least. They should never actually get down to Chicago. The Mississippi River is a massive torrent all year long in the ice ages.
Its the ice volume building up and the volume drawing down and then how much time it takes for a full build-up or a full draw-down. As an example, the southern third of Greenland is going to melt out if this interglacial lasts another 5,000 years and it is going to melt out completely if the interglacial lasts a further 25,000 years after that.
http://s16.postimg.org/63v3fs8xx/Last4_Ice_Ages_Milankovitch.png
Bill, you say ” the summer sun is almost the same as today” however at the time an interglacial starts perihelion is advancing towards NH summer solstice while obliquity is increasing. Currently perihelion is in NH winter just after the winter solstice and obliquity is decreasing. Those differences are what determines whether we are heading into or out of an interglacial. The third piece of course is eccentricity, which is now low and that show allow this interglacial to linger a while longer; similar to the one 400,000 years ago.
Also your chart show summer insolation at 75N. Isn’t the standard 65N?
Tom in Florida, the difference in the solar insolation in the Milankovitch Cycles is extremely small. For Chicago, it is a difference of something like 160 kms north or south. The summer sun in Chicago in the deepest downturns of the Milankovitch is like the summer sun in Milawaukee today (a little farther north than that actually but anyway) And then the winter solar insolation in Chicago is actually higher, something like Lafayette Indiana. It is almost no change at all.
That is why I use 75N, because that is the latitude where 160 kms of difference makes a difference between the snow and ice melting or not. It doesn’t make a difference at 65N. 65N snow stops melting in the summer when there is 500 metre high glaciers and permanent sea ice at 70N, thousands of years after there is 500 metre high glaciers at 75N.
http://s18.postimg.org/9zec2vst5/Milwaukee_Lafayette.png
Bill, do you have a source for the nice chart and the Milankovitch data plotted on it? While there seems little doubt that Milankovitch is exerting some control, there are in fact a number of significant departures as well suggesting that the orbital influence is rather loose. The 100,000 year cycles in fact vary in length by quite an amount – I’m away to dig out the numbers that didn’t make my final cut.
Eyeballing this chart it seems there should have been an interglacial around 225,000 that for some reason got delayed.
Bill
Complicated is the wrong word. Nonlinear-chaotic is the term you are looking for.
As Tsedakis concluded, the glacial inception at MIS 11, an analog of our own at a node of low amplitude eccentricity oscillation (as well as MIS 19) that interglacial 400 kya was “not prolonged by subdued insulation forcing” (his words). What this means is that the magic number of 420 w/m2 may not have been reached but the interglacial ended anyhow.
With nonlinear oscillatory systems the absolute numbers are less important.
So I agree with try that the super long interglacial that you are calling which essentially means the end of the current Pleistocene glaciation, is very unlikely. What makes this even more so is the fact emphasised by Maslin and Ridgewell 2005 that this glacial period far from having ended is in fact deepening. The MPR (change from 40 to 100 kyr interglacial spacing) is part of this.
I meant “I agree with tty ” not “try”.
I hate smartphone spellcheckers.
Here is where I have the T peaks
8135
128357
237975
322638
410483
I have numbered cycles on my charts 1 to 4, here are the cycle lengths:
1) 120222
2) 109618
3) 84663
4) 87845
The beginning of cycle 4 could be wrong since it is at the bottom of the core (maybe not beginning of cycle). But its that cycle 2/3 boundary that looks like it might be “in the wrong place”.
euanmearns, I’m using the numbers from Huybers 2006. A simple index of the summer solar insolation above 400 W/m2 at 75N. Below 400 W/m2 is not enough to melt the snow from the winter. It is more-or-less the same as the 65N measure one will have seen but this is a more physically realistic measurement in my opinion. We can be reasonably certain about these numbers for +/- 5 million years. Beyond that, there is too much uncertainty.
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/huybers2006insolation/j_75north.txt
Other latitudes at:
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/huybers2006insolation/
Bill:
You underestimate the insolation change over orbital cycles. The 65N TOA insolation change reached over 80 watts/m^2 at 65N.
Here is my favored explanation. Likely Orbital cycles began the NH cooling. This then stopped the AMO, which brings much of the heat into the Arctic. As the Arctic began to ice over, albedo increased, causing further cooling. During max glaciation, the Arctic (e.g. Greenland ice cores) chilled by a few 10s of deg-C, but the globe chilled by only several deg-C. When the NH receives low TOA insolation from the 21-kyr apsidal precession of the eccentricity cycle, the SH receives more TOA insolation. (see my earlier comment). NH glaciation was largely the consequence of decreasing all forms of energy input — insolation from orbital and possible changes, ocean currents, especially the AMO, and increased albedo. These factors complicate the effects of the orbital changes alone, and may produce irregularities in precision of the effects of orbital alone.
Further, the orbital cycles are complex. Likely cycles are predicted at ~21, ~41, ~100, ~125, and 400 kyr, which may interact with one another.
During warming from glaciation, all these effects are reversed. T
hus ice melting is driven by more than just TOA insolation from orbital cycles.
Euanmearns
About interglacial timings, this paper by Maslin and Ridgewell 2005 has an interesting take on the MPR:
http://sp.lyellcollection.org/content/247/1/19.short
In short the post-MPR ~100,000 yr spacing is not simple eccentricity forcing but a complex interaction of precession forcing with “pacing” by eccentricity. This is typical of weak nonlinear forcing by multiple impulses.
Note also that the MPR change from 41 kyr to 100 kyr periodicity is also indicative of progressively deepening glaciation. At some future time we may transition to permanent glaciation.
Euanmearns:
“The beginning of cycle 4 could be wrong since it is at the bottom of the core (maybe not beginning of cycle). But its that cycle 2/3 boundary that looks like it might be “in the wrong place”.”
Not to worry. MIS 7 was a rather atypical interglacial, appreciably colder than MIS 1, 5, 9 and 11, and consisting of three separate peaks MIS 7a, 7c and 7e (7.1, 7.3 and 7.5). In the Vostok curve 7e at c. 235 KA BP looks very dominant, but other records are much more ambiguous and the “true MIS 7” might well have been 7c at c. 215 KA BP or 7a at c. 195 KA BP instead.
It was the weakness of MIS 7 (= low sea level) that was the reason that this interglacial long remained unknown and outside the “classical” Penck-Brückner four-glacial scheme.
A very different interpretation suggests itself from Bill’s glaciation versus insolation graph. Most interglacial a peak with maximal insolation but as insolation sharply falls there is a “jagged forward projection” as temperatures unstably persist at interglacial levels despite falling insolation, rather like cartoon figures running of a cliff but staying “air-running” at the same level till they look down, notice the drop beneath them and duly fall.
This means the interglacial will likely end imminently. This will happen when the climate “looks down” and notices that insolation no longer supports interglacial conditions.
A number of commenters here are clearly better informed than I am about many of the details. But here’s a few of my hunches. Whilst accepting that insolation matters, I remain unconvinced it is the over riding driver. Heat is transported to high latitude in the Atlantic by The Gulf Stream. The rotation of the Earth then takes that warmed moist air over Europe and beyond. Where I am sitting right now, Aberdeen Scotland, was under 3 kms of ice about 12,000 years ago. At about 1000 m altitude today we enter Arctic conditions. The survival of winter snow in the mountains is determined by how much snow falls in winter and by how mach rain falls in summer. Sunshine and insolation appear to play a minor role. It seems to me that atmospheric circulation pattern and the Gulf Stream are all important.
Euan,
On your Dec-29th comment, I agree that ocean circulation and amount of snowfall are important. But something is required to BEGIN NH glaciation. A warm and possibly open Arctic Ocean and North Atlantic will furnish moisture for snow. Ocean current will furnish heat. But when that ocean heat is turned off, the northern oceans grow cold and evaporation for new snow is curtailed.
Further, for land glaciation to begin in earnest, summer temperature must fall significantly below that of today, or snow melts away. Other than Greenland (which is already glaciated) most NH land lies at low elevation (e.g. much of northern Canada and northern Euro-Asia). So, how does one get BOTH ample snowfall and lower temperatures in summer to preserve that snow and turn it to ice?
My suggestion is an orbital cycle drops summer temperature over land. But ocean currents (from the still warm tropical and southern oceans) continue for awhile into the northern oceans to keep the sea unfrozen and evaporation available. So ice accumulates on land; the sea level falls. At some point falling sea level (most sea entry into the Arctic occurs over shallow continental shelf, which becomes land with falling seas) and falling NH temperature turns off the northern flow of the warm Atlantic current and snowfall begins to be reduced.
My point is that a factor is required to lower NH land temperature to initiate NH glaciation. Once begun, other factors become partially controlling. These other factors also disrupt a simple relation between glaciation times and orbital cycles.
Comments?
“Further, for land glaciation to begin in earnest, summer temperature must fall significantly below that of today, or snow melts away”
Not really, there are at least two highland areas where a very slight lowering of summer temperatures would be sufficient to initiate large ice-caps:
1. Baffins Land (known to have been snow-covered for long periods during the LIA, fortunately not long enough to initiate glaciation)
2. Putorana Plateau in northern Siberia
Hope I have this reply in the right place.
A starting point is a popular theme of mine and that is that ordinary folks perception of climate change can be heavily influenced by where they live. Where I live in NE Scotland I really can’t see much change in the 50+ years I’ve lived here. If you live in southern California it’s different.
My main point is this. Where I live the Gulf Stream, N Atlantic Current, thermohaline circulation, whatever you want to call it is paramount in keeping us warm. The Shetland Islands, the most northerly bit of Scotland, is at the same latitude as Oslo in Norway (where I lived for 8 years enjoying the baking hot summers) and S Greenland, where I’ve never been. But Norwegians went there on vacation 1000 years ago.
I think if you live in N America you view and think about the problem from a different angle. From where i’m sitting, ocean circulation is paramount, and that is likely influenced by atmosphere circulation. And from what I’ve said else where on this thread, that may be controlled by the thermal structure of the atmosphere.
Solar forcing of winter climate variability in the Northern Hemisphere
Sarah Ineson1*, Adam A. Scaife1, Jeff R. Knight1, James C. Manners1, Nick J. Dunstone1, Lesley J. Gray2 and Joanna D. Haigh3
NATURE GEOSCIENCE | ADVANCE ONLINE PUBLICATION | http://www.nature.com/naturegeoscience
For those still reading this, I wanted to point out just how strong the Sun is in the summer at my favourite latitude of 75N (or 80N in this case). Let’s put some real numbers on it.
Eureka Nunuvut Canada radiation tower data throughout the year 2009. Eureka has a world-class climate research station.
Around the peak solar radiation date of June 21, the Sun is coming in about 500 W/m2 (give or take cloudiness). If you live in Chicago, the summer solar radiation will be something like 950 W/m2 so this is much much lower strength.
The snow still on the ground in Eureka until mid-June is reflecting back something on the order of 70% of this sunlight. So the net solar radiation that is actually influencing the surface temperature (or melting the snow) is only about 100 W/m2 rising slowly to 200 W/m2 but by mid-June the snow melts and the full 450 W/m2 (after Albedo) or so is coming in. It slowly declines to about 200 W/m2 in August and then the snow comes back by the end of August and all the solar radiation is reflected away again.
These numbers need to fall by about 25 W/m2 or so before the snow stops melting out in the summer. Then glaciers will start building up and the increased reflection of the Sunlight means a self-fullfilling ice age will start (unless the Milankovitch Cycles switches back rapidly). This is not going to happen for probably 125,000 years. There will be a small decline in this solar radiation (of less than 1.0 W/m2 really) in the next 3,000 years and then it will go back up again before falling to slightly less than today 52,000 years from now. It will then promptly go back up until the big decline happens in 125,000 years.
http://www.esrl.noaa.gov/psd/arctic/observatories/eureka/img/eureka.tower.2009.png
I suspect sea ice may have something to do with this. As Salby has shown, the major fluxes of CO2 come from absorption / desorption from the oceans, and if anything interferes with absorption of CO2 by the northern oceans, it will cause CO2 to persist in the environment. Sea ice could have just that effect.
http://www.environment.harvard.edu/docs/faculty_pubs/tziperman_sea.pdf
I have a few problems with this (excellent) post:
1. In Figure 4 CO2 lags temperature but the lag appears to increase toward the base of the core. There is no real discussion of errors / calibration issues. Is there a calibration problem with the older ice (compression, contamination etc)?
2. In Figure 6 around 110,000 years ago there is a discontinuity in the temperature curve that, if you eliminate it, makes the two curves match much more closely. So is the discontinuity real or is the departure of the two curves real?
3. The lag between T and CO2 is not as convincing in Figure 6 as it is for the whole time series in Figure 4. Again can there be a calibration problem with CO2 and time (as you go back in time CO2 time error increases)?
4. The T curve has many more data points than the CO2 curve. What happens when you display the two curves with data points representing only the same years (i.e. a sub-sampling of the T curve)?
1. The larger lag at the end of MIS 11 (fourth interglacial back) is more likely due to the unusual length of this interglacial.
2. No discontinuity. Just a very quick temperature rise at the beginning of the MIS 5c interstadial.
4. Not possible. Temperature and CO2 analysis was not usually done at the same points in the ice-core. It would be possible to use only the closest temperature points (leading or lagging). I’ve done it, and it doesn’t really make much difference.
tty,
4. It’s possible if you’re not afraid of interpolating. The “safer” way to do it is as Steve from Rockwood suggests: use the CO2 timescale as is and interpolate T. It doesn’t make much difference, but if you’re really finicky about accuracy you’ll get better results this way than by choosing only the leading or lagging T value.
Steve from Rockwood,
In general, the further back in time, the greater the time uncertainty. The Petit 1999 Vostok CO2 data show an interesting pattern; the time resolution is lower (more years btw data points) at lower CO2 levels, which sort of makes sense — need more ice to accurately detect a smaller concentration of gas. The average resolution of the entire CO2 record is 1,460 years, but the worst time resolution is within the most recent 100kyrs of the record — four of the 6 data points with > 5,000 years between them are in this interval, and the average is 2,200 years. Very oddly, the best time resolution is between 200-330ka, nothing above 3,000 years, average 960.
More recent lead/lag studies use cores from Siple Dome and/or Taylor Dome which don’t go back as far (~22ka for Siple, ~62ka for Taylor) but which have better time resolution. Shakun et al. (2012) — I think mentioned in this thread somewhere — is a multi-proxy study which gets more representative global temperatures and higher resolution CO2 from EPICA Dome C in Antarctica. They find that temperature leads CO2 in the SH, but lags in the NH. Sort of a push-me-pull-me sloshing thing going on.
Shakun’s paper is a joke, as anyone with practical experience of radiocarbon dating (and other applicable geological dating methods) can tell you. They are not nearly exact enough to correlate distant proxies with the kind of precision needed. This is particularly true during the Late Glacial when changes in the carbon cycle caused a millenium-long “radiocarbon plateu”, making all dates from the Younger Dryas interval extremely ambiguous.
The dating methods for ice cores (beyond varve-count range) are also rather inexact, but this doesn’t really matter as long as you only use CO2 and temperature measurements from the same core since the errors affect both equally.
Shakun’s goal was very simple – destroy and eliminate palaeo climate data from the climate discussion. His method was to smear together dozens of proxy datasets, some so weak that they hardly show a difference between the Holocene and preceding glacial maximum, in order to create a homogenised blended meaningless curve from which any information about prior climates was ironed flat, crushed and destroyed.
Shaking should be in prison.
Shakun. not shaking.
How do you turn off the f***ing spellchecker from iPhone?
tty, as a prestigious journal with a reputation to protect, Nature does not publish “jokes”.
Phlogiston, results which don’t fit your chosen narrative are not a priori fraud.
Brandon Gates:
For your information I originally started doubting the CAGW narrative when I found that Nature does publish “jokes”. This happened when Nature published a number of CAGW-related papers that partially involved my own field of study (Quaternary Geology) and which were so factually and methodologically bad that they should under normal circumstances have been instantly turned down by the reviewers.
By the way if you know of any evidence that radiocarbon dates from the Late Pleistocene actually have the kind of precision Shakun et al. thinks seem to think they have I would be most interested in references.
tty,
I don’t typically trust the alleged qualifications of nameless folk on the Innerwebz, but in this case I allow a small exception: as a credentialed geologist you should know that the way to more robust results is to use multiple dating methods.
Well, I’d start with reference 13 from Shakun 2012, which is: Lemieux-Dudon, B. et al. Consistent dating for Antarctic and Greenland ice cores. Quat. Sci. Rev. 29, 8–20 (2010).
I can’t find an open access .pdf of the entire paper, but the data and abstract are available from NOAA’s paleo archive: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/lemieux-dudon2010timescales.txt
ORIGINAL REFERENCE:
Lemieux-Dudon, B., E. Blayo, J.-R. Petit, C. Waelbroeck, A. Svensson,
C. Ritz, J.-M. Barnola, B.M. Narcisi, and F. Parrenin. 2010.
Consistent dating for Antarctic and Greenland ice cores.
Quaternary Science Reviews, Vol. 29, Issues 1-2, pp. 8-20, Jan. 2010.
doi:10.1016/j.quascirev.2009.11.010.
ABSTRACT:
We are hereby presenting a new dating method based on inverse techniques, which aims at calculating consistent gas and ice chronologies for several ice cores. The proposed method yields new dating scenarios simultaneously for several cores by making a compromise between the chronological information brought by glaciological modeling (i.e., ice flow model, firn densification model, accumulation rate model), and by gas and ice stratigraphic constraints. This method enables us to gather widespread chronological information and to use regional or global markers (i.e., methane, volcanic sulfate, Beryllium-10, tephra layers, etc.) to link the core chronologies stratigraphically. Confidence intervals of the new dating scenarios can be calculated thanks to the probabilistic formulation of the new method, which takes into account both modeling and data uncertainties. We apply this method simultaneously to one Greenland (NGRIP) and three Antarctic (EPICA Dome C, EPICA Dronning Maud Land, and Vostok) ice cores, and refine existent chronologies. Our results show that consistent ice and gas chronologies can be derived for depth intervals that are well-constrained by relevant glaciological data. In particular, we propose new and consistent dating of the last deglaciation for Greenland and Antarctic ice and gas records.
Soooo, good old-fashioned convergence hard at work again. What happens when one overly-focuses on their own expertise is it often becomes easy to miss miss what else has been done to address the weaknesses of the particular method in question.
Indeed, we now have several alternative dating methods (OSL, U/Th, K/Ar and AAR to mention the most common ones). Unfortunately they are all less exact than 14C, and so not much use for “tightening up” chronologies (beyond establishing that 14C accumulation has indeed been non-linear beyond the currentl range of calibration curves).
The only methods that are more precise that 14C are varve counts and treering counts. Even these have some uncertainty, but less than 14C which is why they are used for calibration of the 14C record.
Personally I prefer uncalibrated 14C dates, except for comparisons with historical records and other dating methods. This is mainly because calibration curves keep changing and “calibration” is a mathematically irreversible process, i. e. one can always recalibrate a “raw” 14C date, but there is no way to convert a calibrated date back into a “raw” date, or re-calibrate it according to a newer (and better) calibration curve. A lot of people (particularly archaeologists) are unaware of this.
I am familiar with Lemieux-Dodon et al. and the follow-up AICC 2012 time scale. The methodological descriptions sound very fancy (it is of course a Bayesian technique), but basically it is a matter of interpolation between dated tie-points. What is new is that the interpolations are (slightly) non-linear based on glaciological modelling which is certainly an improvement, and that they “wiggle” tie-points to obtain best fit between records which is rather doubtful methodologically. Furthermore AICC 2012 depends strongly on orbital tiepoints so it is not really independent of the Milankovitch curve.
Also in constructing the time-scale glaciological parameters for Greenland were “tailored” to force the resulting timescale to fit to the GICC05 timescale based on varve-counting in the NGRIP core. GICC05 is admittedly not absolutely precise, but maximum error is very well constrained. This apparently required rather unlikely glaciological assumptions for some time intervals. Without this “tailoring” the two timescales would have differed by up to 400 years. So, as so often with Bayesian statistics, it is basically a question of selecting the “correct” prior.
tty,
L-D mention in their abstract: … glaciological modeling (i.e., ice flow model, firn densification model, accumulation rate model), and by gas and ice stratigraphic constraints. This method enables us to gather widespread chronological information and to use regional or global markers (i.e., methane, volcanic sulfate, Beryllium-10, tephra layers, etc.) to link the core chronologies stratigraphically.
Stratigraphy I’m already familiar with from my lay childhood hobby of rockhounding. How that translates into glaciology may not be the same beast, and I understand chemostratigraphy, which relies on isotope ratios, is a relative newcomer. That would seem to cover U/Th and K/Ar from my naive point of view. Totally clueless about OSL and AAR. Dunno if Shakun or any references cited in his 2012 study rely on any of those.
Now that I’ve told you what I think I understand and lots more about what I don’t, it doesn’t ring true to me that a suite of dating methods is only as strong as its strongest link as you imply above. Perhaps you could expound.
I’m guessing that varve counting in ice cores is problematic because the layers get smeared. Even if not, the constraint would be that a single annual layer of ice wouldn’t yield up enough trapped gasses to get a reliable count. Am I in the ballpark?
That’s what raw data are for, yes? I do see a plethora of competing time scales in NOAA’s paleo ftp archives and I gather that the bulk of them are not ginned up from freshly gathered samples but from reworking raw data from previously done field work.
You should know that fancy stats techniques don’t much impress me in and of themselves. Much of that is due to ignorance of anything beyond basic frequentist descriptive stats and simple significance tests, so what I don’t understand implicitly translates into default skepticism. Interpolation generally is not something which falls into that default bucket for me, particularly when applied to physical systems. If I can’t believe that the first principles of physics at work here are sound enough to use as modeling constraints, I may as well give up on most scientific findings since Newton. To say nothing of Planck who did as much as say he could find no reason to conclude that physical laws won’t change tomorrow just for the heck of it.
You say that like it’s a bad thing. I see Milankovic’s work as one of the more elegant explanations set forth to explain the past million years or so of ice-age cycles. The result is a quite short list of mathematical formulae with great predictive power; a rarity in climatology. To throw out such a solidly regular timer which also embeds rate and magnitude of change over time in a field where seemingly intractable uncertainty abounds strikes me as exactly the worst possible thing for a paleochronologist to do.
Here is the point where a specific citation would be lovely so I can read and decide for myself.
I’m confused, that sounds like one of those good problems to have.
Such as? Again, citation?
Ah yes, there’s always that. One hopes that the “correct” prior is the one which best explains the bulk of observations. Probably not a good idea to arbitrarily cast aside too many observations as you and some of your compatriots would apparently have Shakun do.
B. Gates says:
Nature does not publish “jokes”.
It published MBH97/98, didn’t it?
Steve, I’m running short on time now. My quick answer to your points is to look at Figure 5 where CH4 and CO2 are determined on same samples and CH4 is a proxy for the temperature curve.
I don’t understand your point 3.
Over a shorter time period the lag between CO2 and T does not appear to be so large. Could there be an issue with CO2 in the older (deeper core) where the bubbles have somehow migrated up the ice. If you were to stretch the CO2 curve you could better match CO2 and T versus time with less lag. I guess my point is that these data sets seem to be taken as error free measurements.
In looking at all these temperature graphs, they look like sawtooth oscillator output to me from my years of looking at scopes. Is it possible they are indicators of power pulses traveling through plasma? That would provide a mechanism for periodic heating and cooling over almost any time scale. The shape of the pulse is very closely tied to the mechanics of how the pulse was made.
Brant
“The spiral structure of the Milky Way, cosmic rays, and ice age epochs on Earth
Nir J. Shaviv
Nir J. Shaviv
Racah Institute of Physics, Hebrew University, Jerusalem, 91904, Israel; Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Str., Toronto, ON M5S 3H8, Canada
New Astronomy (Impact Factor: 1.85). 01/2003; DOI: 10.1016/S1384-1076(02)00193-8
Source: arXiv
ABSTRACT The short term variability of the galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way. Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages. This picture has been recently shown to be supported by various data [PhRvL 89 (2002) 051102]. In particular, the variable CRF recorded in Iron meteorites appears to vary synchronously with the appearance ice ages.Here, we expand upon the original treatment with a more thorough analysis and more supporting evidence. In particular, we discuss the cosmic ray diffusion model which considers the motion of the galactic spiral arms. We also elaborate on the structure and dynamics of the Milky Way’s spiral arms. In particular, we bring forth new argumentation using HI observations which imply that the galactic spiral arm pattern speed appears to be that which fits the glaciation period and the cosmic-ray flux record extracted from Iron meteorites. In addition, we show that apparent peaks in the star formation rate history, as deduced by several authors, coincides with particularly icy epochs, while the long period of 1 to 2 Gyr before present, during which no glaciations are known to have occurred, coincides with a significant paucity in the past star formation rate.”
http://www.researchgate.net/publication/222828472_The_spiral_structure_of_the_Milky_Way_cosmic_rays_and_ice_age_epochs_on_Earth
More compelling evidence that the wrong tree was chosen by the barking hound.
The entire discussion here comes down to the time lag between gas sealing and ice formation. I have read before that barometric changes on the snow-ice surface cause the near surface to “breathe” for only 70 years; here the number is 2000 or more. The variation would seem to be in the speed that snow first become ice and then the ice loses all its permeability; this would probably reflect net snow retention and aspects of humidity (the interstital spaces need to be filled to seal the entire column).
I can see from the thoughts above that different ice cores would, at different times, have different lag times. Ice layers should be, like tree-rings, correlatable, but the lag times would still be individual. Adjustments would still be needed. I get the idea this has not been done.
The lag time between deposition of ice – the hydrogen isotope data – and the sealing of the ice column – methane and CO2 content in bubbles – is the critical parameter. The apparent 800-year lag that is not top-and-center of our discussions suggests to me that the lag time is THE “unsettled” scientific parameter being avoided by at least the warmist camp. I say “at least the warmist camp” because the lack of focus on this subject makes me worried that the skeptic camp of note are concerned that the lag might disappear with focused research.
I believe we are being lied to in all the CAGW discussion. The question we have to ask ourselves as skeptics, is not how much the warmists are lying (which they are) but how much we are being lied to by the people “on our side” also (not being informed is the same as being lied to when our support is on the line). There are things that don’t make sense, and not just things that come from a Gore, Hansen or Suzuki.
Doug
Here is part of a comment I may far above.
There are limited data for some ice cores (don’t know about Vostok) on N2 and Ar isotopic fractionation during diffusion from gas bubbles. These presumably give temperature contemporaneous with the time of entrapment of CO2. The lag time between temperature to CO2 is much less, but interpretation uncertainties still are too large to say they are exactly contemporaneous.
This implies that a significant part of the time difference between snow deposition and CO2 closure against diffusion in bubble is caused by the time required to actually seal CO2 in bubbles.
Euan,
Except they do discuss it:
There is a close correlation between Antarctic temperature and atmospheric concentrations of CO2 and CH4 (refs 5, 9). This discovery suggests that greenhouse gases are important as amplifiers of the initial orbital forcing and may have significantly contributed to the glacial–interglacial changes 14–16
The overall correlation between our CO2 and CH4 records and the Antarctic isotopic temperature 5,9,16 is remarkable (r^2 = 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 15,16 .
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. 44 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/iceage 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.
Our results suggest that the same sequence of climate forcings occurred during each termination: orbital forcing (possibly through local insolation changes, but this is speculative as we have poor absolute dating) followed by two strong amplifiers, with greenhouse gases acting first, and then deglaciation enhancement via ice-albedo feedback. The end of the deglaciation is then characterized by a clear CO2 maximum for terminations II, III and IV, while this feature is less marked for the Holocene.
No, they just don’t reach the conclusions you’re looking for.
Review the charts again and note that temperature generally rises much faster than it falls, what the authors call a “saw-tooth” pattern. There is proper understanding to be found by pondering the implications of the differences in slope.
Brandon, The gradient of warming at terminations is usually not to different to the gradient of cooling post-interglacial. Petit et al do discuss the general lag (600±400 years) and correctly say that this cannot be resolved within the errors of dating. The elephant in the room I’m talking about here is exclusively the 8000 year lag that occurs each time the earth is plunged back into glacial episode. This is clearly not subject to dating errors since the CH4 and CO2 are measured on same samples. Petit et al do identify this big lag but then as far as I can tell ignore it, chosing instead to focus on the general lag that Jo Nova and others discuss that is more easy to dismiss.
I got the feeling that the conclusions of the Petit paper would have been the same regardless of the data. And it is trying to prove something that drove Shakun to their data manipulation.
Euan,
Between 110 and 140 Ka, summertime insolation at 65°N rose to a peak, and then declined at a slope steeper relative to the rise. Temperature, which I find lags insolation by about 3,500 years, followed the exact opposite pattern — relatively steep rise, relatively shallow decline:
https://drive.google.com/file/d/0B1C2T0pQeiaSb3VMMWJnZGpMUVE
A similar series of events occurred between 65-90 Ka. Note throughout these data that GHG concentrations tend to persist in the atmosphere once they’ve been introduced even as temperatures are dropping sharply due to steep falloffs in insolation. The general rule is that temperature and GHG rises are steeper than the increase in insolation, and declines are shallower than the declines in insolation.
Insolation drives the timing of trend reversals and directionality, GHGs (and albedo feedbacks, etc., not shown in this plot) affect the slope and amplitude. It’s a quite clear and easy to understand relationship when one looks at the appropriate data all in one place at the same time.
Petit and friends do discuss it here:
An intriguing aspect of the deglacial CH₄ curves is that the atmospheric concentration of CH₄ rises slowly, then jumps to a maximum value during the last half of the deglacial temperature rise. For termination I, the CH₄ jump corresponds to a rapid Northern Hemisphere warming (Bölling/Allerød) and an increase in the rate of Northern Hemisphere deglaciation (meltwater pulse IA)43. We speculate that the same is true for terminations II, III and IV. Supportive evidence comes from the δ¹⁸Oₐₜₘ curves. During each termination, δ¹⁸Oₐₜₘ begins falling rapidly, signalling intense deglaciation, within 1 kyr of the CH₄ jump. The lag of deglaciation and Northern Hemisphere warming with respect to Vostok temperature warming is apparently greater during terminations II and IV (~9 kyr) than during terminations I and III (~4–6 kyr). The changes in northern summer insolation maxima are higher during terminations II and IV, whereas the preceding southern summer insolation maxima are higher during terminations I and III. We speculate that variability in phasing from one termination to the next reflects differences in insolation curves 41 or patterns of abyssal circulation during glacial maximum.
Properties change in the following sequence during each of the last four glacial terminations, as recorded in Vostok. First, the temperature and atmospheric concentrations of CO₂ and CH₄ rise steadily, whereas the dust input decreases. During the last half of the temperature rise, there is a rapid increase in CH₄. This event coincides with the start of the δ¹⁸Oₐₜₘ decrease. We believe that the rapid CH₄ rise also signifies warming in Greenland, and that the deglacial δ¹⁸Oₐₜₘ decrease records rapid melting of the Northern Hemisphere ice sheets. These results suggest that the same sequence of climate forcing operated during each termination: orbital forcing (with a possible contribution of local insolation changes) followed by two strong amplifiers, greenhouse gases acting first, then deglaciation and ice-albedo feedback. Our data suggest a significant role of the Southern Ocean in regulating the long-term changes of atmospheric CO₂.
GHGs are not sources of heat. At the surface they act as insulators which reduce the rate at which absorbed solar energy can be emitted back out to space as long-wave radiation. When incoming long-wave radiation from the Sun, the expectation is that temperatures will rise more rapidly and to higher levels than if GHGs were not present. Conversely when incoming LWR decreases, the expectation is that temperatures will not fall as quickly or to as low a level when higher levels of GHGs are present in the atmosphere.
This is not motivated thinking, it’s first principles of quite standard, long-standing, tried and tested thermodynamic physics.
It’s also entirely consistent with the data I’ve plotted.
Mods, etal,,,
Sorry to go off the subjet: But…
Just watched the TV show America Unearthed, with Scott Wolter. Show about possible Ming explorer getting to N. America prior to Columbus. Nice show some evidence this and that about rock walls, maps and stuff.
So after it went off I checked in internet on this Scott Wolter. Found this site:
scottwolteranswers.blogspot.com
http://www.scottwolteranswes.com
hope one othose is correct
Any how there is a back and forth between Scott Wolter and a guy from “In Search of Giants” TV show.
James Colavito , today around noon shows Dec. 27, 2014 at 11:12 and it started on 26th.
Scott is saying the ones of China got here first.
The back and forth there is very much like here. Sort of of intrest seems.
Sorry to go off the subject.
.
The “academic trivia” is in “Who got to the Americas first”?
Rather, the real question is “Who made a difference discovering the Americas?”
Did it matter if the Vikings landed first? No – They did nothing with their landing.
Did the “native Siberians” get here first? Absolutely! They had several wide-ranging (and very destructive!) civilizations and cultures all over from the Arctic to the Strait of Magellan. But did nothing else.
Did the Chinese get here? Maybe. Maybe. So what? They did nothing with their possible landing.
Did Columbus’ discovery in 1492 matter? Yes! Everything worldwide changed. Immediately.
http://www.jasoncolavito.com/blog/review-of-america-unearthed-s03e07-marco-polo-discovers-america
oops
http://www.scottwolteranswers.com
A cursory glance at your first chart shows that a drop of 2to3k puts us in an ice age. The fools in the alarmist camp are worried about a bit of warming, makes one wonder if they have all their marbles. Thanks for your good work.
Wayne, Proxy data indicate that global temperature was only several degrees lower than today’s, but Arctic zone temperature was lower by a few tens of degrees, according to Greenland ice cores. And orbital data predict that the southern hemisphere during NH max glaciation was receiving higher solar energy. An ice age is not the same globally.
“An ice age is not the same globally.”
Prehaps not the same, but it is global. Glaciations and interglacials in the Southern Hemisphere occurr at the same times as in the Northern. Yes, there are leads and lags, but that is true on a smaller geographic scale as well. The latest ice-age started about 5,000 years earlier in Northern Europe, sompared to Southern Europe.
Actually there is strong reasons to believe that the scale of glaciation in Antarctica is directly tied to NH glaciation, since it seems to be regulated more by sea-level change than temperature,
To tty comment below:
I agree. When TOA insolation is low in the NH the world glaciates. When TOA is low in the SH little occurs. That is why I think ocean currents play a significant role in moving heat. See my reply above to Bill posted several minutes ago.
instead of thinking in terms of arctic perafrost, think in terms of a swamp.
When heated, it rapidly rots giving off methane and CO2.
When cooled, rot slows and so does photosynthesis.
It’s that photosynthesis that’s the issue on the downside.
A fast growing tree can suck down all the CO2 above it in just a few years. Cold and dead trees don’t do that. Warm ones do. So in cold and cooling world, less plant life absorbs the CO2.
EM
As I suggested upstream, at glacial inception I can think of one more process that would have similar effect in decreasing CO2 uptake and increasing supply. Sea levels would fall rapidly so that the shallow seas with high primary plankton productivity would be drained and become exposed mud. They would rot and stink for a while before eventually becoming covered in terrestrial vegetation.