A detailed analysis of temperature, CO2 and methane variations from the Vostok ice core is presented for the time interval 137,383 to 102,052 years ago. This captures the termination of the glaciation that preceded the Eemian interglacial and the inception of the last great glaciation that succeeded the Eemian. At the termination, CO2 follows dT exactly, but at the inception CO2 does not follow temperature down for 14,218 years. Full glacial conditions came into being without falling CO2 providing any of the climate forcing. This falsifies the traditional narrative that dCO2 amplified weak orbital forcing effects. It is quite clear from the data that CO2 follows temperature with highly variable time lags depending upon whether the climate is warming or cooling.

Methane on the other hand lags temperature by about 2,000 years at the termination but follows temperature down exactly at the inception. It therefore follows that methane and CO2 are not coupled. Each responds in their own time to changing climate. The absence of coupling may be explained by the different bio-geochemical pathways these gasses have in the biosphere – ocean – atmosphere system.

Introduction

The Vostok Ice core is one of the finest geochemical data sets ever assembled. I first visited this topic in December 2014 in a post called The Vostok Ice Core: Temperature, CO2 and CH4 [1]. For background information on Vostok, readers are directed to that post.

One of the key observations I made was that at the inceptions of the last 4 glaciations, CO2 lagged temperature by several thousand years:

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 post has now had over 8000 reads and is probably one of the most read texts on this subject. And yet the Climate Science community continues to ignore the fairly profound implications of what the data actually shows. Since the clout and reach of this blog has grown tremendously since 2014, the time seemed ripe to have another go.

Figure 1 Temperature and CO2-co-variance in the Vostok ice core [1]. The general picture is one of quite strong-co-variance, but in detail there are some highly significant departures where temperature and CO2 are clearly de-coupled. This is the focus of this post. The grey band is the part of the ice core record examined here. Note that in this chart and all others time is passing from right to left, counter to the normal geological convention, which is a restriction imposed by XL charts that have two primary y-axes. An alternative image showing time passing from left to right is provided in the Appendix at the end of this post.

Figure 1 shows one of the summary charts from my earlier post [1]. What we see are large cyclical swings in temperature of over 10˚C and by adjusting the scale appropriately, we see similar cyclical swings in CO2 concentration. But what is the cause and what is the effect? Does change in temperature and ice cover cause CO2 to change or does changing CO2 cause temperature to change? The climate science community has adopted the latter into their narrative, where very weak orbital factors trigger the cycles that are then amplified by changing CO2 and methane. This post will demonstrate beyond reasonable doubt that this part of the climate science narrative is untenable and should be dropped.

A note on terminology: The glacial episodes both begin and end very rapidly. The end of a glacial episode is called the “glacial termination” while the beginning of a new glacial episode is called the “glacial inception”. In the text below this may be abbreviated simply to “termination” and “inception”.

Looking at the data more closely it is easy to see that dCO2 lags dT by some considerable amount, especially at the inceptions of glacial episodes (see the arrow labeled inception). The time lag has received much attention, especially from the sceptic community, who realise that this greatly weakens the warmist narrative. For example, Jo Nova had a post called The 800 year lag in CO2 after temperature – graphed [2], where she recognised and graphed a general time lag of several hundred years between CO2 and temperature but missed the much larger time lags at the inceptions.

Time lags of a few hundred years can be explained by dating errors and calibrating the gas ages to the ice ages (see my earlier post). This has caught the attention of the climate science community and for example Parrenin et al (2013) [3] revised the gas ages in Vostok over the time interval 10,000 to 22,000 years ago that spans the termination that preceded the Holocene interglacial where the established chronology already showed good alignment between CO2 and T (Figure 1). Parrenin et al conveniently forgot to examine the relationship at the inception where the time lag of several thousand years is so large, it is not possible to explain it by a calibration error.

The subject of this post, therefore, is to look closely into the relationship between T, CO2 and CH4 in a narrow time band that spans the pre-Eemian termination and post-Eemian inception.

Data

In order to make my points, the data are presented in stages via a series of charts that hopefully makes my argument easier to follow.

Figure 2 Vostok dT and dCO2 over the post-Eemian glacial inception.

Let me begin with temperature and CO2 over the post-Eemian inception (see the grey band in Figure 1). Time is passing from right to left. The data series begins at 128,300 years, that is standing right on the pinnacle of the Eemian temperature maximum and things were about to get really cold while CO2 does virtually nothing but trend sideways for thousands of years. The next chart is annotated and puts numbers on the story.

Figure 3 An annotated version of Figure 2.

The right hand box marks 128,300 years ago that is closest to the T peak. CO2 had been a little higher a short while before, but on the temperature peak a value of 274.1 ppm is recorded at a time when dT registered +2.78˚K. The lefthand box marks 114,082 years ago, chosen because this is the end of the sideways CO2 trend. In the 14,218 years that passed, CO2 changed not at all while temperatures plunged 7.23˚K and full on glacial conditions were established.

The onset of the last glaciation is one of the most profound climate events in human history and this data demonstrates that CO2 played no part in it. The Climate science narrative of weak orbital triggers being amplified by CO2 is proven to be false.

The Milankovitch orbital forcing, while almost universally accepted to play a part, is far too weak to explain the glacial cycles it describes. If it is not orbital forcing and it is not CO2 forcing then there must be some other process to explain the data and Earth’s recent climate history. I will get to that later in the post.

Figure 4 Vostok dT and dCH4 over the post-Eemian glacial inception.

At this point it is convenient to shift attention to methane (CH4). Figure 4 shows the same time interval and dT series as Figure 3, but this time plots CH4 instead of CO2. We see a remarkable coupling of CH4 and temperature at the post-Eemian inception. The main point here is that climate scientists cannot fix the disagreeable data in Figure 2 by adjusting timescales without completely destroying the beautiful coherency of dT and CH4.

Did a fall in CH4 of 200 parts per billion cause the last Glaciation? Of course not! What happened is that the high latitude bogs in the N hemisphere froze over shutting off the main source of atmospheric CH4. More on this later.

Figure 5 Expanding the timescale by 12,253 years reveals the true complexity of the relationship between temperature and CO2. See text for details.

Before moving on to look at the termination, I want to extend the CO2 inception story by expanding the time scale by 12,253 years to 101,829 years ago (Figure 5). The temperature – CO2 story can now be divided into three segments. Segment 1 shows the data from Figure 2 and covers the interval from Eemian T max to where CO2 stopped moving sideways. Segment 2 is defined by an interim T low of -7˚K, 108,000 years ago. In the time interval 114,082 to 108,000 years ago CO2 did fall as a complex interaction between the freezing / cooling biosphere and the oceans eventually pumped CO2 down. But then in segment 3 something remarkable happens. Temperature rebounds a little while once again CO2 tracks sideways. It should by now be abundantly clear to all that CO2 has little to do with modulating temperature during glacial cycles.

Figure 6 This chart extends the picture shown in Figure 2 back in time to include the glacial termination starting at 137,383 years ago.

Finally I want to take a look at the relationships at the termination, when the glaciation ends, and the large N Hemisphere ice sheets collapse and melt. We find that temperature and CO2 are very closely aligned (Figure 6). As the oceans warm, CO2 is exhaled immediately. Whilst as already described at the inception, CO2 is not pumped down by the cooling oceans until over 14,000 years have passed.

At the termination, methane on the other hand is not so closely linked to temperature, but it does rise as a consequence of warming with a time lag of a few thousand years (Figure 7). More on that later.

Figure 7 Same as Figure 6 but showing CH4 instead of CO2.

Figure 8 A plot of CO2 and CH4 over the same time interval as shown in Figures 6 and 7 illustrates how these two gasses are loosely coupled at the termination and are decoupled at the inception.

And finally, if we compare CO2 and CH4 we find that they are not coupled (Figure 8). Both do rise in response to warming but not at the same speed and as we have already seen, CH4 falls at the inception in line with temperature while CO2 does not. When one considers the different bio-geochemical processes that moderate atmospheric CO2 and CH4, the lack of coupling between the two is not surprising.

Discussion

In attempting to combine these various bits of information into a coherent model, the following factors need to be taken into account:

CO2 and temperature are closely coupled at the glacial termination, both rising together CH4 and temperature are less well coupled at the glacial termination, CH4 rising up to 2000 years after temperature CO2 is decoupled from temperature at the glacial inception remaining constant for over 14,000 years while temperatures plunge over 7˚K CH4 is closely coupled with temperature at the glacial inception, both falling together At the onset of the glacial termination 137,341 years ago, albedo is high owing to extensive ice sheets but the next thing to happen is that temperatures rise At the onset of the glacial inception 128,357 years ago, on the peak of the Eemian interglacial, albedo is low but the next thing to happen is that temperatures fall Variations in CO2 and CH4 need to be explained by bio-geochemical processes combined with temperature variations and changing land and sea ice cover CO2 and CH4 are responding in different ways to events and therefore have different sources and sinks The overall pattern of glacial cycles are controlled by Milankovitch orbital cycles, but these alone are too weak to account for the large temperature fluctuations

The following interpretation is speculative. The main source of atmospheric methane today are high latitude wetlands where bacteria produce methane in large quantities [4]. At the peak of the glacial episodes, these wetlands would either be frozen or under ice. Much of these wetlands will have been incorporated into a vast belt of permafrost along the margins of the ice sheets.

I am going to speculate that the main source of methane at the termination is derived from melting permafrost and that the time lag reflects the different kinetics of melting a collapsing ice sheet and melting permafrost that we know can linger for many thousands of years after a glaciation has ended as evidenced by the widespread existence of permafrost today.

Figure 9 Natural sources of atmospheric CH4 today in million tonnes per annum. Wetlands dominate while ocean sources are relatively minor [4].

Figure 10 Map of global wetlands [5].

Melting permafrost would also be a source of CO2. Why then do CO2 and CH4 not rise together at the glacial termination. Here we must recognise that CO2 has many different sources and sinks and the data suggest the existence of a much larger source that swamps the permafrost signal. At the termination, there is a vast upheaval in the global biosphere as temperatures climb and climate and vegetation zones march northwards, this could give rise to a complex pattern of CO2 production and sequestration. Overall, one might expect that the mass of the terrestrial biosphere would rise during the interglacial and that this would tend to lower CO2, the opposite of observations.

I am going to speculate that the main source of CO2 at the termination is the oceans and that this is so large it overprints CO2 emitted from melting permafrost and CO2 sequestered by the biosphere. It is well-established that the ability of water to hold CO2 is linked to temperature, where cold water can hold significantly more. The rise in temperature of the upper layers of the oceans was several degrees as recorded by d18O in benthic foraminifera (Figure 11). Thus, warming oceans will exhale a large quantity of CO2 causing CO2 to rise in close lock step with temperature.

Moving on to the glacial inception, as the planet cooled down, the high latitude wetlands that will have formed during the Eemian combined with on-going melting permafrost will freeze over quickly closing off the main source of CH4 that falls in close lock step with temperature as the frozen area progressively expands. But why then does CO2 not follow temperature and CH4 down?

Here we need to call on a combination of processes. The first is that it is easier for oceans to exhale CO2 than it is for it to inhale. Absorbing CO2 occurs only at the surface layer and requires convective ocean currents to remove it from the surface and sequester it in deep water. Exhaling CO2 on the other hand can occur throughout the whole volume of ocean water with CO2 transported to surface by diffusion. Think about opening a bottle of Champagne. It is much easier to release the gas than it is to put it back in the bottle. An argument can be made for asymmetric time scales where the rate of production at the termination is far greater than the rate of sequestration at the inception. But this still does not explain why CO2 stays exactly constant for over 14,000 years. Here we need to consider what is going on in the terrestrial biosphere. A vast Boreal forest will have sprung up during the Eemian. This will now be progressively dying back releasing CO2 to the atmosphere while glaciers advance eroding soils adding more CO2. The speculative interpretation, therefore, at the inception is that slow removal of CO2 by the oceans is balanced by slow addition of CO2 from dying vegetation and soil erosion. Eventually the oceans win as the sources become exhausted and following 114,082 years ago atmospheric CO2 is eventually pumped down.

The most significant aspect of this narrative is that the Ice Age begins without any help from CO2. Low albedo and high CO2 does nothing to prevent the Ice Ages from beginning.This tells us that there is some other mighty force that is responsible for plummeting temperatures at the inception and having established that some other mighty force exists, it seems likely that this same force is responsible for the terminations too, and all the upheaval in between. And we know that this force is linked to orbital cycles but that these cycles do not directly cause the glacial episodes.

I can think of only two mighty forces that could be implicated and that is the Sun and ocean currents, specifically thermohaline circulation. A number of studies show that variations in solar geomagnetic activity are correlated with a 1200 y climatic cyclicity in the northern hemisphere. These cycles persist during the glacial and inter-glacial episodes. During the glaciations they are recognised as Dansgaard Oeschger evenst in Greenland ice cores [6] and during the inter-glacial as Bond cycles in N Atlantic ocean sediments [7]. We know some of the Bond cycles as the Little Ice Age, Medieval warm Period, Dark Ages cold period and the Roman Warm Period. However, there is no evidence from the cosmogenic isotope record that large-scale changes to the Sun causes the glacial episodes. That leaves ocean currents as the prime candidate. This should not be a controversial suggestion since the climate science community is always warning that Man’s activity may cause the North Atlantic current to close down bringing us an Ice Age instead of global melt down.

How can ocean currents link to orbital cycles? At this point I want to introduce our analysis of the orbital cycles as recorded by the LR04 d18O benthic foraminifera stack that we published in the 2016 edition of The Alpine Journal [8]. The traditional view of the orbital cycles is that they were controlled by the 41,000 year obliquity cycle before switching to the 100,000 year eccentricity cycle about 1.2 million years ago. No one understands how or why this works. Physicists do their analysis by using statistics while geologists tend to look at logs and introduce their experience in how they should be interpreted. We marked peaks and troughs in the d18O profiles and there is certainly a degree of subjectivity in this exercise. And then we measured the time intervals between the peaks and troughs.

Figure 11 Glacial cycles as recorded by fluctuations in global ocean temperature as recorded by d18O variations in benthic foraminifera. [8, 9]. Click image to get a very large readable format. Note that time passes from left to right on this chart as it should do.

Figure 12 A summary of the duration of glacial episodes from LR04 as logged in Figure 11 [8].

The results of this exercise are illustrated in Figure 12. We find no evidence for the existence of the 100,000 year cycle. Instead we see dominance of the 41,000 year obliquity cycle and multiples thereof. 82,000 year cycles are recognised throughout but these come to dominate about 1.2 million years ago – 82,000 years and not 100,000 years. And then most recently we have a 123,000 year cycle. But we also have a problem since glaciations are sometimes in phase with obliquity and sometimes out of phase [8]. Finding the holy grail of understanding the glaciations completely has eluded us. The glaciations beat to a 41,000 year tempo while evidently not being controlled by it.

At this point I want to conclude by presenting a simple hypothesis that I cannot as yet fully explain. Thermohaline circulation of the modern era is somewhat a miracle of the natural world and depends upon a delicate balance of moving ocean water from tropics towards the poles, evaporation that increases salinity, the formation of sea ice that increases salinity even more causing cold saline water to sink and flow along the ocean floor. This is the engine that drives thermohaline circulation. The evidence suggests that changes in obliquity somehow upsets this delicate balance causing the system to either shut down or to begin. For the last 1.2 million years, there has been greater resistance to circulation being triggered and the glaciations have become substantially longer in duration.

The change to ocean currents has profound effect on the pattern of atmospheric circulation where greater convection rates and increased cloud cover may both contribute to rapid cooling or vice versa. During the glacial episodes we would not recognise the distribution of pressure systems as belonging to the Earth we know today. CO2 in the past played a negligible role. It simply responded to bio-geochemical process caused by changing temperature and ice cover.

References:

[1] The Vostok Ice Core: Temperature, CO2 and CH4 Energy Matters

[2] The 800 year lag in CO2 after temperature – graphed Jo Nova

[3] Synchronous change of Atmospheric CO2 and Antractic temperature during the Last Deglacial Warming Parrenin et al 2013, Science

[4] Climate Science of Methane: Oxford

[5] Wetlands map: McGill

[6] Solar influence on glaciation in Greenland Energy Matters, and references therein.

[7] Bond Cycles and the Role of The Sun in Shaping Climate Energy Matters, and references therein.

[8] Alpine Journal 2016: The Shrinking Glacier Conundrum by Mearns E. and Milne A.

[9] Lorraine E. Lisiecki and Maureen E. Raymo 2005. A Pliocene-Pleistocene stack of 57 globally distributed benthic D18O records. PALEOCEANOGRAPHY, VOL. 20

Appendix

Figure 1a Roger Andrews who is a geologist like I am was confused by my Figure 1 that shows time passing from right to left while the geological convention is from left to right. I explained to Roger that this is imposed by XL where you cannot change the sense of the X-axis scale using the two primary Y-axis scale chart format. Roger somehow managed to change this manipulating the image, not XL.