Inconvenient: New paper finds the last interglacial was warmer than today – not simulated by climate models

[Reposted from the Hockey Schtick]

A new paper published in Climate of the Past compares temperature reconstructions of the last interglacial period [131,000-114,000 years ago] to climate model simulations and finds climate models significantly underestimated global temperatures of the last interglacial by ~0.67C on an annual basis and by ~1.1C during the warmest month.

This implies that climate models are unable to fully simulate natural global warming, and the error of the underestimation is about the same as the 0.7C global warming since the end of the Little Ice Age in ~1850. Thus, the possibility that present-day temperatures could be entirely the result of natural processes cannot be ruled out in comparison to the last interglacial period.

Further, during the last interglacial, Greenland temperatures were naturally up to 8C higher and sea levels up to 43 feet higher than today. And, during another interglacial, all of Greenland and West Antarctica melted & sea levels were 79 feet higher. Since this low-CO2 global warming occurred entirely naturally, there is no evidence that global warming during the present interglacial is unnatural or man-made.


Temperatures during the last interglacial period ~120,000 years ago were higher than during the present interglacial period.

Table_last IG

First column is the warmest single period simulated by climate models, second column is the warmest period from a compilation of temperature reconstructions.

Clim. Past, 10, 1633-1644, 2014


Last interglacial model–data mismatch of thermal maximum temperatures partially explained

P. Bakker and H. Renssen


The timing of the last interglacial (LIG) thermal maximum across the globe remains to be precisely assessed. Because of difficulties in establishing a common temporal framework between records from different palaeoclimatic archives retrieved from various places around the globe, it has not yet been possible to reconstruct spatio-temporal variations in the occurrence of the maximum warmth across the globe. Instead, snapshot reconstructions of warmest LIG conditions have been presented, which have an underlying assumption that maximum warmth occurred synchronously everywhere.

Although known to be an oversimplification, the impact of this assumption on temperature estimates has yet to be assessed. We use the LIG temperature evolutions simulated by nine different climate models to investigate whether the assumption of synchronicity results in a sizeable overestimation of the LIG thermal maximum. We find that for annual temperatures, the overestimation is small, strongly model-dependent (global mean 0.4 ± 0.3 °C) and cannot explain the recently published 0.67 °C difference between simulated and reconstructed annual mean temperatures during the LIG thermal maximum.

However, if one takes into consideration that temperature proxies are possibly biased towards summer, the overestimation of the LIG thermal maximum based on warmest month temperatures is non-negligible with a global mean of 1.1 ± 0.4 °C.

The full paper is available here:


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‘This implies that climate models are unable to fully simulate natural global warming,’ although to be fair their always able to simulate some global warming even if none has happend in reality .


It’s looking like the models, like the algorithms for working with the surface temperature data, are working as designed…cool the past, warm the present.


Thanks, downloaded. This is not news to a geologist but might spread the news.

Leo Smith

Well it is all getting a bit awkward to maintain the orthodoxy isn’t it?
Worse, it looks like human activity in the holocene has, if anything, prevented global warming!
Oh dear oh dear.

We can’t tell if the broad optimum of 400,000 years ago is simply due to lower resolution available from the older ice, but the decrease in temperature since the Holocene optimum is more gradual than since the three previous optima. Given that humans have changed much of the earth’s surface since the Holocene optimum, and don’t like to freeze, I conclude that we have prevented some global cooling.


Anthropic Principle. If temps had plunged after the Optimum, civilization wouldn’t have developed and you wouldn’t be reading this board.


One of the misleading aspects of discussing the periodicity of the major glacial epochs is the fact that we tend to think of them as “the same” – a cycle repeating. None of the major interstadials are the same in structure, though some are more like another than others. Although Milankovic cycles are the most accepted current explanation of the major ice ages, there are also some serious questions that are not explained, most importantly variability. I keep hoping to see an analysis that applies Edward Lorenz’s work to the question.

September 2, 2014 at 3:02 pm
Kevin Trenberth was a doctoral student of Lorenz, which shows how much use chaos theory is.
Milankovitch Cycles explain variability adequately, IMO. The parameters haven’t yet all aligned the same, so variability is inherent in the system. However, the most important variables do roughly repeat every ~400,000 years, so many researchers consider that the Holocene should most closely resemble the interglacials of MIS 11 and MIS 19.
I assume you mean interglacials rather than interstadials.

Are these temperature estimates reasonable?
Talk of 0.01C detail information from proxies?
An error range of?
+/- 0.4C?
Temperature reconstructions versus model simulations?
Can we actually define a temperature change of 12C from 100 000 years ago?
+3 t0 -6C about which zero?
To me this is more illusion, the average global temperature pretence.
The claimed range and accuracy defy the data so far presented.
Or did I miss a key piece of information?


This is nothing new. It has been well known for decades that the Eemian interglacial period was globally, 3 C warmer that our present day Holocene, and that sea levels were much higher. I am very disappointed in this new generation of scientists who are either terrible researchers, or are just recycling the already known.

more soylent green!

You’re not saying it’s settled science, are you? /smile
Confirmation never hurts. What if they did the study and found otherwise?


I am saying that this is an established part of climate history, and established through many different sources. The AGW crowd has tended to ignore such history in the past, and has taken to climate history revisionism, e.g., the elimination of the Medieval Warm Period in Mann’s hockey stick graph.

Steve Keohane

I thought this was known for at least two decades. Here is a 15 year old graph:

Every paleoclimatologist knows that the Eemian was warmer and so far longer than the Holocene, and most also know that MIS 11 and 19 were warmer and longer than the Eemian. During the latter two interglacials, the southern dome of the GIS melted away. The Holocene might be another long-lasting interglacial, like those two, since they were at about 400,000 year intervals and the Milankovitch Cycles have again lined up in about the same configuration as then. However the Holocene’s peak warmth was not as hot as during those two or the Eemian.
The point of this paper isn’t that the Eemian was warmer than the Holocene, but that GCMs cannot reproduce the temperature regimes of that interglacial or those of MIS 11 and 19. This should come as no surprise. They also fail even more miserably to reproduce the hot, equable climate of the Cretaceous Period.


Thanks for elaborating.


About the amplitude modulation of eccentricity – yes at the low nodes such as now and 400 kya the interglacial seems to be wider. Its also noticeable that at the high amplitude nodes e.g. 200 and 600 kya instead of a clean sharp interglacial that you might expect you get an unstable double headed pair of warm intervals.
The current interglacial being of lower amplitude may be linked to the kong term trend of deepening glaciation which presumably continues. For the lasy 3 my of glaciation, for the first 2my interglacial spacing was 41 ky following obliquity, then for the last million yrs interglacials have become less frequent only every 100 ky following eccentricity. Also the glacial intervals are becoming deeper with the last one being the deepest. The trend is down.

Brian p

Human activities preventing global warming what an interesting idea

M Courtney

Although this sounds like a killer bullet for the “we hare living in unprecedented warming” script., I have my concerns.
This still seems like it has models at its heart. And at first glance I don’t see how the models are validated by the proxies. How reliable are the proxies from that long ago, anyway?
However, I am an ignorant layman and am willing to be convinced that my concerns are just unfounded, prejudiced scepticism.

Here are some mega-proxies showing the reality of greater warmth and higher sea level during the Eemian:
1) Scandinavia was an island (which is why Lakes Saimaa and Ladoga have ringed seal populations).
2) Hippos swam in the Thames at the site of London.
3) Raised beaches in Alaska.

M Courtney

Ok. It was hotter back then.

Steve R

Studies in Florida indicate Eemian sea level stood between 18 and 30 feet above modern sea level. These are by no means new revelations.

David B

I’ll give you the hippos, but are you sure the higher sea levels in Scandinavia and Alaska weren’t just due to incomplete rebound of the land from glaciation?

David B:
Yes, I’m sure.
Higher sea level was because of warmer seas and partial melting of GIS & WAIS relative to the Holocene.
Not just on those continents with ice sheets but on unglaciated continents and oceanic islands sea level was higher than now. I considered adding Bermuda to my list. Guess I should have done so.


M Courtney, here is an example of a hardcore proxy.
“A new record of Pleistocene hippopotamus from River Severn terrace deposits, Gloucester, UK—palaeoenvironmental setting and stratigraphical significance
A new Pleistocene vertebrate assemblage from fluvial deposits of the River Severn in Gloucester, England, has yielded the remains of hippopotamus (Hippopotamus amphibius), a new record for this terrace system, ”
……….”Hippopotamus is also present in the German Rhine during the Eemian Interglacial”……..


Here’s another.

Abstract – 23 June 2006
…From applications of both correspondence analysis regression and best modern analogue methodologies, we infer July air temperatures of the last interglacial to have been 4 to 5 °C warmer than present on eastern Baffin Island, which was warmer than any interval within the Holocene. On these grounds, we ascribe the lower lacustrine unit in these lakes to the climatic optimum of the last interglacial, ca. 117 to 130 ka BP (Marine Isotopic Stage 5e)….

Oh the heat was so destructive.


Models are not per se the enemy. Poor models, bad models, and models based upon mistaken assumptions are. All knowledge effectively consists of “models.” We tend to think of facts as “real” and what we know, but in reality, what we think we know derives from interpreted experience, either our own or someone else’s. The word “fact” itself derives from the same route as “manufactured.” It refers to experience converted to (made into) an interpretation – a model in essence. Evidence is empirical, facts are not. It is empirically evident that pushing an object off a table, a ladder, or a cliff will result in it falling. Galileo established that “something” acts similarly on all masses in a vacuum. Newton published a theory of gravity which attempted to systematize and generalize what we “knew” from experience – ad hoc and systematic – to universal scales. Newton’s law of gravity is simply a model. Unlike a climate model however, it only starts to deviate from reality at very large scales of time over great spans of time – see Modified Newtonian Dynamics just for fun.


The findings of this paper mean nothing. Any sentient human long ago realized that the AGW thesis is a VERY well funded, organized , left wing / neo-communist POLITICAL movement .
The polar ice caps could tomorrow increase in areal extent by 100% and all we would hear from the AGW zealots would be how human generated CO2 caused it.
By the way, do not be surprised in the slightest if we learn that Putin’s Russia is a major funding source and propaganda supporter of the AGW thesis. What better way for this thug to guarantee a good market and prices for HIS oil and gas, as Western Europe systematically commits energy suicide and becomes ever more reliant on Russian oil and gas.


If Putin follows the findings of his Russian scientists, he would be leaning more towards the projected global cooling side than that of the AGW crowd. His annexing of Crimea, which contains large ice free natural harbours, was not a random move, in my opinion.

If you understand that the world is likely to cool, you disrupt your enemies by getting them to believe that it will warm.

more soylent green!

The Soviet Union funded several dissident and radical organizations in Europe and the USA during the Cold War, so this would have precedent.

Mike Maguire

Though this is interesting, I find these studies that go way back in time, suggest having unveiled more significant information, with more precise measurements, than the reality of the science that exists to obtain it.
Climate models in real time the past several decades have already provided overwhelming evidence that they are lacking in skill. Going back over 100,000 years to rate their skill, whether it confirms or shows the opposite gets very little weight in my assessment of global climate models.
There could have been numerous other unknown factors present in the distant past that makes the explanations to account for this data speculative.
We can be extremely confident that the earth was much warmer/colder and oceans much higher/lower and have a good idea on “general” time frames. However, I think mechanisms to explain why or how are very speculative and could have been completely different than current conditions, which would negate usefulness as examples to compare with today.


Mike Maguire writes:

We can be extremely confident that the earth was much warmer/colder and oceans much higher/lower and have a good idea on “general” time frames. However, I think mechanisms to explain why or how are very speculative and could have been completely different than current conditions, which would negate usefulness as examples to compare with today.

If you don’t know the mechanisms that caused the earth to be warmer/colder and oceans higher/lower, how would you know if they are properly account for in current climate modeling? The finding does not negate the usefulness of these findings, but emphasizes today’s lack of knowledge about such findings that may be relevant for today.

Mike Maguire

“The finding does not negate the usefulness of these findings, but emphasizes today’s lack of knowledge about such findings that may be relevant for today”
Let me rephrase a prior statement to be more clear(my fault earlier).
The results/conclusion with regards to specific explanations and precise values stated are, in reality, often highly speculative but stated in terms of confidence levels that greatly exceed their true value.
This makes them potentially misleading. A number of unknown factors, introduce uncertainty that grows with time. There is certainly great value in these studies and I did not mean to suggest no usefulness. However, that usefulness is sometimes overstated because it’s expressed with more certainty implied than should be expressed when viewing particular elements of the results.

Tim in Florida

Mike, how is that pretzel contortion working out for you. You have definitely come up with a new way to justify the continued gravy train.


My bad.
I have read – somewhere – that ‘The Science I S settled’.
And, here, perhaps, there is a known unknown. Or two – ish.
Even a swarm of unknown unknowns.
Well, Michael M.; Al G.; who would have thought it?
[Good Moderator – the excessive use of question marks and exclamation marks is not needed here, I believe, whether on stylistic or other grounds.]
Not sure if this needs a /Sarc. tag. But mentioned . . . . . . .


Excuse me? Were they asserting that they can reconstruct monthly average temperatures 100,000 years ago from proxy data?
I want some of what they’re smoking.
This sounds like a classic high frequency vs low frequency data error, turned into a paper. I wouldn’t expect that 100,000 year data to be accurate to the year, let alone the month. I would further have to question the error bars — how, exactly were these computed?
Finally, when one refers to “the models” what models are they talking about? To the best of my recollection, we don’t have any models that can reconstruct even the approximate pattern of warming and cooling over the Pleistocene ice age including the shifts from 22-26 ky cycles to 41 ky cycles to 90-100 ky cycles and the associated significant deepening of the glacial trough:
let alone the last 65 million years (scroll down a bit to see). Milankovich is the usual assumption, but it has a very hard time functioning as a sufficient explanation, especially given:

Constructions of this kind are common. However, they assume that ice volume is driven by changes in insolation, and such data therefore cannot be used to establish the existence of such a relationship.

For once in the Wikipedia page, this is stated up front. A model is required to transform the proxy data obtained into an estimate of global temperature such as this graph, or the graph(s) shown above (which just reprint the usual Vostok ice core data). That model makes assumptions about synchronicity, how e.g. ice volume can be related to sedimentation rates, how ice core bubbles trap gases, how much diffusion occurs between adjacent layers over 100,000 year plus time intervals (note well the smoothing of the Vostok curves as they go into the more distant past!) and above all, the causes of the glacial cycle, e.g. Milankovich periodicities that can be fit to the data.
One cannot, then, use the data to prove that Milankovich cycles are the proximate cause of the Pleistocene glaciation. If I have noisy data and fit it to a quadratic model, I cannot use the quadratic model curve to prove that the noisy data was quadratic. It’s then a self-fulfilling prophecy.
So I’m not certain what the top article is really trying to accomplish with its comparison. Is it asserting that the models for geological time climate change are inadequate to explain the data? Of course they are — everybody knows that. Are they asserting that such already inadequate models as exist “might be” sufficiently accurate that we can resolve late-20th-century-possible-CO_2-driven warming from garden variety natural climate evolution? Don’t make me laugh. We can’t even reconstruct or explain the last 20,000 years with a believable ab initio physical model, let alone the last 100,000, 600,000, 3.5 million, 5 million, 25 million. We have little more than fond hopes of ever doing so, as the time resolution of the 25 million year data might be no better than the time frame of the entire Holocene — radiometric dating gets increasingly imprecise as one goes back in time, good to centuries, thousands of years, even tens of thousands of years when one gets way back there.
All we can say is that it is reasonably probable that the last interglacial was both on average and in marginally resolvable bursts warmer than this interglacial, in particular the present. Even in this interglacial:
it is highly improbable that the present is the warmest period in the Holocene — again the figure caption quite honestly indicates that the black curve and the various colored curves have highly limited temporal resolution — smoothed to 300 years! — and the wide range of the different proxies strongly suggests that the probable standard error in even the 300 year smoothing is often/usually at least 0.5 C. This means that the actual high resolution inferred temperature excursions are at least the square root of the autocorrelation time divided into 300 times larger. If we assume a dominant/shortest autocorrelation time of perhaps 10 years, the actual warmest decades were probably as much as 2-3C warmer than the black curve, although there were equally probably decades that were this much colder — the underlying data does not look terribly synchronous. Again, one has to be careful to completely ignore the high resolution data spliced onto the ends as “the present” as those single year data points or decadal trends cannot meaningfully be compared to any part of 300 year windowed data (which, I will point out, is twice as long as the entire thermometric record).
The only useful information in the article above is that in previous interglacials, sea levels were 10 to 20 meters higher than they are now. That is data that is a) difficult to argue with, as it is direct observational data that can be confounded only by profound changes in ground level that one can relatively easily determine independently and correct for (and which are accompanied by commensurate swings in the ice sheet, which are also quite soundly recorded by proxy data, and of course by the radiometric data). In a sense, this renders the issue concerning models moot, if they weren’t already. As the top article notes, one way or another sea levels can go up 10 to 20 meters above their current level in an interglacial, without carbon dioxide, and, since we have no functional models that can explain the timing or severity or detailed evolution of the glacial/interglacial cycle in the first place, with or without CO_2, it is pointless to assert that there is some sort of “cap” on the currently observed climate state that cannot or would not be exceeded without increased CO_2.
This does, in a Bayesian sense, reduce the probability that the current warmth is strictly due to increased CO_2. I could formulate a theory such as “prayer works to cure cancer”. I could have a very serious physical model for an all-powerful God who could, if they wished, cure cancer in any individual or prevent cancers from ever occuring, but who chooses to actually refrain from doing so unless petitioned by prayer. I could then easily go out and find a dozen people who had cancer and who prayed and who were cured. Indeed, I might well find that nearly all of the people whose cancer went into remission or who survived for 10 years after surgery or other therapies prayed for a cure at one time or another. I could present this as powerful evidence that prayer works to cure cancer!
Except that it isn’t. One can count so very many flaws in this (common enough) religious argument. But the biggest difficulty is that there is no control group, and no double blind experiment, and no effort to even do proper epidemiological work on broad data to determine how prayer alters a baseline non-prayer-based survival rate. The existence of a large group of humans who did not pray (but whose cancer was cured anyway) is, in fact, evidence against the hypothesis. The demonstration that a suitable non-praying population that has a survival rate indistinguishable from an equally suitable praying population within their mutual standard errors would actually be strong evidence of the exact opposite — that whether or not God does or does not exist (Bayesian prior number one), whether or not God can or cannot cure cancer (Bayesian prior number two), it is actually extremely unlikely that God uses “I was prayed to for a cure” as the criterion for acting to cure cancer, if indeed God ever acts to cure cancer at all.
So the good thing about the geological record of the climate is that functions, or rather should function, as a sort of control group to confound assertions that greatly exceed the range of reasonable inferences supported by the data. When the daily high temperature outside in Durham, NC on any given calendar day of the year can fluctuate by an easy 20 or 30 C (depending on the time of year) according to the historical record, it isn’t really fair to state that just because the weather has been nice and comparatively cool for two weeks (or, in the current case, an entire summer) that a sudden warming is evidence for anything at all. “Random chance” (or if you prefer, entropy in the system associated with our lack of its precise state or time evolution) can easily explain it without any need or possibility of asserting a specific proximate cause.
This is why Mann’s work was so important to the IPCC, so important that it became cover art. Humans actually are pretty good at doing Bayesian statistics in their heads. If today’s temperatures are within spitting distance of MWP, RWP, or Holocene Optimum temperatures, if previous interglacials were even warmer than this one for reasons utterly beyond human control since humans had not, properly speaking, evolved yet, certainly not in any significant numbers, it becomes significantly less likely that the present requires some special explanation because it is in some sense “unusual”. That doesn’t mean that there might not be some special explanation, only that its logical or mathematical necessity becomes easy to doubt, and the predictions made on the basis of that special explanation are substantially “weaker” (less likely to be correct) than they would be if there was a fluctuation that is actually far out of the range of those observed in the past temporally synchronized with the special explanation. Mann — as apparently suggested by some of his peers — managed to find a data model that erased the MWP and LIA, rendering the past behavior smooth enough to fool a gullible public, including a gullible public of scientists who should have known, and done, better once it became clear which way climate funding cookie was crumbling.

Milankovitch Cycles didn’t cause the Pleistocene glaciations. Plate tectonics are largely responsible for that, chiefly the closure of the former Strait of Panama into the Isthmus thereof. Milankovitch Cycles do however control the waxing and waning of the NH ice sheets, once the Pleistocene got started.
The Cenozoic glaciations, of which the Pleistocene NH ice sheets are a part, were also initiated in the Oligocene by plate tectonics, mainly the opening of deep oceanic channels between Australia and South America on the north and Antarctica on the south. Some also see a role for the collision of India with Asia, raising Tibet and the Himalayas.


This is all plausible, sure, but can you direct me to a model that quantitatively reproduces any significant portion of this curve without being pure Fourier numerology? I don’t doubt that closing the Strait was a proximate cause, but why was it a proximate cause. Also, why did it proceed so slowly, with shifting periodicities? Why did it convert to ~100 ky cycles some million years ago, with a very substantial deepening of the low temperature troughs? How can one explain why the Eemian is warmer than the Holocene, but other interglacials are cooler, including some that didn’t really quite get out of glaciation? How can one predict the “expected temperature” of the planet given its orbital data upon which to even start building a detailed model of the actual process after adding on the other factors — prior state (a huge one!), atmospheric composition, variables that we don’t even realize are important/necessary to the models because we simply lack any data or any possibility of ever getting data to explicate them, or even reveal to us their importance — 100,000 years ago, or at the start of the Younger Dryas.
This isn’t to criticize work on this subject — only to point out that paleoclimatology models don’t really “work” without a lot of a posteriori glue and bandaids, better for explaining the past, sort of, kind of, mostly qualitatively, than at predicting (hindcasting) the past or predicting the future or making any sort of quantitatively plausible statement about the present.
It is a hard problem, one made more difficult still by virtue of the fact that entropy increases with time and that after 10,000 or 100,000 years, a lot of information that might be used to accurately infer things about climate state is simply gone, erased, or blurred out to where it is not really useful. That’s why looking at individual proxies is so helpful. It lets one see how very inconsistent they often are, how the story they tell (when “suitably selected and averaged”) is at the very least quite vulnerable to error, if not quite an open invitation to cherrypicking etc.
The problem is no different today. Part of the world warms, part cools, all the time, every day. Record high temperatures are set. So are record lows. Record rainfalls. Record snows. We can all see how a single lousy category 1 hurricane in the Atlantic basin — almost the only hurricane to cause any damage at all in the last five or six years — is transformed into the harbinger of doom and offered up as an example of “climate change” by people who should no better. The only real climate change I can see is that the Atlantic is unusually quiet, hurricane-wise, and has been for quite some time now, and I say that after having literally passed through the eye of Arthur earlier this summer (which did almost no damage and was never more than a category 1 storm however it was “promoted” on the basis of a couple of transient gusts). Knock on wood, this is a good thing, but people never trumpet a lack of storms as evidence of global warming, even though it probably is! Not catastrophic enough, you see… and besides, the Pacific has been pretty active. With satellites the contemporary “climate” is difficult to measure or assess. What prayer do we have, really, of getting anything better than 100 year or 1000 year averages from the really remote past?

“Milankovitch Cycles do however control the waxing and waning of the NH ice sheets, once the Pleistocene got started.”
Not quite so simple. There is the major “100,000 year problem” of Milankovitch theory that despite many attempts, really has not been solved.
IMHO this ‘forgotten’ paper may offer a better explanation based upon cosmogenic isotope data: Solar activity
Paper finds solar activity explains climate change over past 200,000 years

Hockey Schtick
September 2, 2014 at 12:48 pm
Naturally, I don’t rule out changes in solar activity as contributory factors in glacial cycles. Activity (irradiance and magnetic flux) is not mutually exclusive with orbital mechanical modulation.
However, IMO evidence is lacking for a purely solar activity-based explanation for the switch from the 40,000 to 100,000 year Pleistocene periodicity around a million years ago. I’d be happy to entertain that possibility, but I haven’t seen it.


I think if you dig in to it in more detail, the “ice age” starts in the Tertiary, perhaps by the beginning of the Pliocene. When the Panama straits close, the Pleistocene pattern emerges with longer, deeper glacials and a lowered global average maximum temperature, possibly minimum as well.


Very nice post. Thanks for that.


This (rgbatduke) deserves a post of its own, it should have a wider audience than just us thread-divers.

Many of his posts deserve article status. I appreciate his calm, well reasoned insight.


I have no idea why the figures I tried to include didn’t make it into the previous post, but here they are again:
The last five million years (basically, the Pleistocene from roughly 2.5 mya to the present, although for some reason they don’t count the Holocene as being part of it even though the named glacial era is almost certainly not over).
Plus then, the Holocene:
In both cases one needs to take the issue of smoothing and high vs low frequency noisy asynchronous data quite seriously. Even in the thermometric era, you can easily see the effect of reduced sampling in a glance at e.g. HADCRUT4 over only 164 or so years. As usual, the graphs don’t provide one with much insight as to probable error in either abscissa or ordinate, although the Holocene is presented as a spaghetti graph that lets one at least make a visual seat of the pants estimate.


I just cut and pasted from my browser, but even the text describing the link was deleted. I’m guessing an anti-spam filter of some sort. Let me try this:
The URL in my browser:
The URL in my browser, in quotes: “”
The URL in my browser, in an anchored link:
Interestingly, your second link (which has exactly the same URL as mine) posts and works fine. Maybe you included it in an anchor?


Hummph, now they all work. Maybe it doesn’t work on a line by itself?
Either way, I’ll stop now.


No; look closely. You’re connecting to the wiki/file: link. That’s not what you want.

As you note, the Holocene is really just another interglacial in a long series of cycles dating back 2.6 million years. It got to be its own epoch basically because humans practicing science live in it. Also, it wasn’t well known in the 19th century how long the current interglacial had lasted compared to glaciations, which at that time were thought to be only four in North America, at least.
The term “Holocene” was first proposed at the third International Geological Congress in 1885. However, many geologists also used the terms “Recent” or “Postglacial” for this epoch until 1967, when the USGS formally adopted the term “Holocene” and discontinued use of “Recent”.


If you asked Michael Mann nicely he would show you how to smooth the whole pleistocene into a horizontal straight line – until the 20th century of course.

don’t be misled by the .PNG at the end of that URL – that’s a webpage not an image – to get the correct URL – right click on the image – and select “copy image address” – or the equivalent in your browser – that will usually save the image path and name to the clipboard


You left out the Pliocene, which precedes the Pleistocene and takes in the earliest 3 MY in your chart. The “Ice Age” actually started in the late Tertiary and carries on through the Quaternary. The Holocene isn’t included largely from custom. When originally defined it was the age of modern man and thus “special.” These days there is a push to insert the “Anthropocene,” which is silly.


OK, obviously a problem for Mr. Moderator. Does WUWT no longer permit embedded links to figures? That’s gonna suck…


I’m like Steve….I swear, I thought we already knew this


Since this low-CO2 global warming occurred entirely naturally, there is no evidence that global warming during the present interglacial is unnatural or man-made.

No, you can’t really say it this way. You can say that the current warming is within the range of naturally occurring conditions, based on historical data. Absence of human influence in the past doesn’t remove the possibility of it happening now.

The article is correct to say

Since this low-CO2 global warming occurred entirely naturally, there is no evidence that global warming during the present interglacial is unnatural or man-made.

Lack of evidence for something does not remove the possibility of that something: it says there is no reason to suppose the possibility is a reality.


“absence of proof is not proof of absence”
is the old saying .

Ian W

It is actually more than that. The IPCC argument is “as we cannot see any other reason for the increase in temperatures except for human emissions of CO2, those emissions caused the warming.” They assume a Kelvinesque or La Place Daemon’s knowledge of all variables.
As soon as it is shown that natural variance – from whatever cause – is equivalent in all respects, or worse still, as in this case it shows warming in low CO2 conditions; then the IPCC argument is falsified as something else does exist outside their knowledge that can provide reason for the increase. As their knowledge is demonstrably incomplete, they are now bereft of supporting logical argument.

J, yes
Ian W, I agree. Well said.
It would be helpful to assuaging the global warming scare if your points were more widely disseminated.

Snip. Sockpuppet. ~mod.
Clearly, you don’t understand logic.
The mentioned evidence says nothing about Bigfoot.
Absence of evidence is not evidence of absence and not evidence of presence. This applies to anything including Bigfoot. Do you have evidence that Bigfoot exists because in the absence of evidence there is no reason to suppose that possibility is a reality?
I repeat that the article is correct when it says

Since this low-CO2 global warming occurred entirely naturally, there is no evidence that global warming during the present interglacial is unnatural or man-made.

because as I said

Lack of evidence for something does not remove the possibility of that something: it says there is no reason to suppose the possibility is a reality.


Snip. Sockpuppet. ~mod.

Snip. Sockpuppet. ~ mod.

lemiere jacques

and each time you look at temperature reconstruction of ice ages, you can think to your self, anything that could warm the worl a bit would be welcome

Dr. Brown:
Milankovitch Cycles reproduce well the strength and duration of each interglacial at least since the switch in periodicity which you cite. The weak interglacials, like those of MIS 7 and 9, are reflected in orbital and rotational mechanics.
Please see Figure 1 in this link:
However, predicting the duration of the Holocene is complicated by the pronounced cooling trend of the past ~3300 years, which if extrapolated would get us back to glacial conditions in a few more thousand years. Based upon Milankovitch Cycles, however, the Holocene could be another multi-precession-cycle interglacial, like those of MIS 11 and 19, which would be good news for humanity, even if it meant some melting of the Greenland Ice Sheet. The southern dome is unlikely to melt completely, as in those prior two interglacials, because the Holocene has been quite a bit cooler.
Every interglacial is unique, so the lesser warmth of the Holocene may mean it ends sooner than the eccentricity cycle would suggest.
The onset of NH glaciation has indeed been modeled, and the results accord well with observations and proposed explanations. To take but one example:
Final closure of Panama and the onset of northern hemisphere glaciation
The Greenland ice sheet is accepted as a key factor controlling the Quaternary “glacial scenario“. However, the origin and mechanisms of major Arctic glaciation starting at 3.15 Ma and culminating at 2.74 Ma are still controversial. For this phase of intense cooling Ravelo et al. [1] [A.C. Ravelo, D.H. Andreasen, M. Lyle, A.O. Lyle, M.W. Wara, Regional climate shifts caused by gradual global cooling in the Pliocene epoch. Nature 429 (2004) 263–267.] proposed a complex gradual forcing mechanism. In contrast, our new submillennial-scale paleoceanographic records from the Pliocene North Atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation (NHG), since it was linked to a 2–3 °C surface water warming during warm stages from 2.95 to 2.82 Ma. These records support previous models [G.H. Haug, R. Tiedemann, Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation, Nature 393 (1998) 673–676. [2]] claiming that the final closure of the Panama Isthmus (3.0– ∼2.5 Ma [J. Groeneveld S. Steph, R. Tiedemann, D. Nürnberg, D. Garbe-Schönberg, The final closure of the Central American Seaway, Geology, in prep. [3]]) induced an increased poleward salt and heat transport. Associated strengthening of North Atlantic Thermohaline Circulation and in turn, an intensified moisture supply to northern high latitudes resulted in the build-up of NHG, finally culminating in the great, irreversible “climate crash” at marine isotope stage G6 (2.74 Ma). In summary, there was a two-step threshold mechanism that marked the onset of NHG with glacial-to-interglacial cycles quasi-persistent until today.

Part of a calibration of models is their ability to track the past. This does not bode well for the models, irrespective of what they want it to do for the future.

jim hogg

The sea level rise clinches it. And there is simply no way of knowing how non-intervention by us would have played out anyway . Therefore any deduction to the effect that an unexpected (why?) temp rise must be due to our contribution just doesn’t do it conclusively . RGB – brilliant as always. Cogent, incisive and eloquent.

Doug Proctor

Although I am skeptical of CAGW, the previous warm periods unrelated to CO2 are not evidence that the current warming is CO2 related, but evidence that other factors can cause warming. If A, then B, (if CO2 then warming) but also if B not necessaarily A (if warming not necessarily due to CO2).
The currrent situation is considered by all warmists as “special”: all “ordinary” factors are minor or neutral in their impact. Only CO2 increaases count, and the CO2 of 1850 was 280 and the CO2 of 2014 is 400. If A then B, that is the basis of the CAGW narrative. Since the IPCC was organized to determine the outcome of warming induced by manmade CO2, the founding assumption or basis is if A then B. Studies such as these are irrelevant to the position taken by the warmists,
Prior heating reasons, if they are determined, could be applied in a “model” to the last 150 years. So far the warmist group have not determined what such reasons could be, and so they cannot fit them into the current analysis. What they have done is determine, mathematically, that the variations of what they do recognize doesn’t do enough to explain much of the recent warming. So they use a perversion of the Sherlock Holmes concept, that once the impossible is eliminated, whatever is left, however improbable it is, must be the answer. Of course this is bad science and bad human reasoning, based on the faulty and arrogant concept that we know enough of everything to reach the correct answer given enough brain power. The conclusion that witchcraft was wild in the countryside was rooted in just the same idea. We haven’t come that much distance from the madness of crowds in 400 years.
At any rate, papers such as this are not, in themselves, proof of anything that diminishes the CAGW position. The cause of prior heating and its relationship to the recent past would be proof that CO2 is not the devil it has been painted to be. That step is where we could hand over material to the warmists and make some headway.

John West

”At any rate, papers such as this are not, in themselves, proof of anything that diminishes the CAGW position.”
Yes it does (sort of). The late 20th century divergence of GAST from models absent of CO2 “forcing” is central to the CAGW narrative and touted as evidence (even though it isn’t) that the late 20th century warming is attributable to anthropogenic CO2 emissions. The claim is being made here that since GAST is underestimated by “the models” from natural warming during the last interglacial it is likely to be underestimating current GAST from natural influences, therefore the much touted divergence is nothing more than their continued lack of understanding of how the climate works rather than CO2 forcing being the only possible reason (lol) GAST is as high as it is.
Although, I have to agree with RGB, this paper doesn’t pass the sniff test any more than alarmist papers.

Reblogged this on Public Secrets and commented:
If this research holds up, it’s utterly devastating to the theory of catastrophic man-caused global warming.


We just couldn’t stand the heat.

The great arc of dispersal of modern humans: Africa to Australia
During the Late Pleistocene, anatomically modern humans (AMH) dispersed out of Africa across the continents. Their routes obeyed the limitations placed on any large terrestrial mammal dependent on daily drinking water, following certain climate-permissive corridors. AMH first spread north, with game, across the Sahara to the Levant during the Eemian interglacial (c.125 ka), but failed to continue to Europe, then occupied by Neanderthals. The savannah ecosystem in North Africa and the Middle East then dried up, and AMH vanished from the Levantine fossil record, being replaced there by Neanderthals. Later, AMH successfully left Africa as a single group by the southern route to India. The added ability to make short but deliberate open water crossings allowed them first to cross the mouth of the Red Sea from Eritrea, and subsequently Wallace’s Line to reach the isolated Sahul continent at least by 48,000 years ago and possibly by 60–50,000 years ago. They only finally arrived in Europe from South Asia around 45–50,000 years ago, probably linked to climatic amelioration during OIS-3.


I guess it’s okay to make stuff up as long as you believe it has to be true. Does Mary Mapes have anything to do with climate modeling?


These very high sea-levels during MIS 11 are essentially fantasies.
This latest paper interprets an absence of IRD (Ice-rafted Debris) as proof of complete deglaciation, while it really only shows that there were no tidewater glaciers, but says nothing about glaciation away from the coast.
Earlier papers which have reported very high sea-levels during MIS 11 have failed to take into account that MIS 11 was much longer (>30,000 years) than any other interglacial and that isostatic rebound had time to go much further than during other interglacials. All sites where such very high sea-levels have been reported are either tectonically unstable or within the “forebulge” zone of the Laurentide ice-sheet.
By the way Hockey Schtick has (as is unfortunately often the case) misunderstood the papers, they don’t refer to the last interglacial but to the fourth-back interglacial (MIS 11)

There is good evidence for the melting of the southern dome of the GIS during MIS 11, which, as you note, was not only warmer than the Holocene, but lasted much longer than our current IG has to date. Also for MIS 19. Both are considered simulacra for the Holocene, based upon orbital mechanics.

“By the way Hockey Schtick has (as is unfortunately often the case) misunderstood the papers, they don’t refer to the last interglacial but to the fourth-back interglacial (MIS 11)”
LOL the post
doesn’t say “the last interglacial” – it says “during a past interglacial” and “sea levels during a “super interglacial” around 400,000 years ago “potentially had a global mean sea level 6 to 13 metres [20-43 feet] above the present level” and the South Greenland ice sheet “was drastically smaller during MIS 11 than it is now, with only a small residual ice dome over southernmost Greenland.”
I meant to link to this post, which found sea levels 29 feet higher than the present during the LAST IG:
BTW links for Greenland 8C warming during the last IG:
All the points made in the post still stand and the HS did not misunderstand the papers contrary to your claims.

So is there any expectation that we haven’t reached the IG maximum?
Any guesstimates on how long this IG is going to last?

I’ll venture this reply, which is just my opinion based upon present state of the evidence.
1) IMO peak Holocene warmth is long past, yet
2) There is a good chance that the current IG will limp along for another 10,000 years or more.
That is, its duration might be similar to MIS 11 and 19, but it hasn’t been and thus probably won’t be, as hot as those IGs, separated by ~400,000 years, as the Holocene is from MIS 11.
If so, this is good news for humanity.


The reconstruction-model discrepancy has already been identified. The authors of this paper are trying to find justifications for altering the reconstructions to match the models.

Steve Oregon

Santer demands extraordinary proof.
“When people come up with extraordinary claims — like the troposphere is cooling — then you demand extraordinary proof,” Santer said. “What’s happening now is that people around the world are subjecting these data sets to the scrutiny they need.”
Funny stuff from 2005:


All they needed to do was send up a balloon with two separate thermometers during the day – one with a sun shield and a 70’s style one without a shield then note the amount of difference between them. I wonder if they ever did anything as straight forward as that?

Find some EE guys, and a few others with degrees and put up the facts on wind and solar electrical production. Show via real transmission and distribution methods how much if any of wind or solar power gets to the normal home in a city or to a bussiness. How much wind or solar elecrictty gets to electric meters after it travles through the transmission and distribution power lines.
For sure make the test run for this with the gas, nuke, oil, water, aka other power sources turned off.
The ones working for the likes of Duke Power or TXU, Chicago Edison , Souther Cal Ed. ect can not and will not tell the truth, as many of the power generation companies are in on the fraud.

William McClenney

Sorry. I saw the word model in the title on ClimPast and moved on. Although it is vaguely interesting, and I do mean vaguely, I am attracted to actual field studies and results from around the world on the Eemian. Heck, we still cannot agree if the last termination (which brought us into the Eemian) was a single or two-step affair. Some say it was stable throughout most of its length and others provide evidence that this was decidedly not the case. I fail to see how models can resolve reality that we still have not fully unraveled in the “real” world.

Reblogged this on Norah4you's Weblog and commented:
More that Swedish “Green” politians (and other politians) had better read before Election Day September 14th……


There were more mammoths and mammoth farts in the last interglacial, as humans hadn’t yet arrived in places like Canada and the US for McMammoth Mcsteakburger.


The 150 000 year graph puts things into perspective, when climate scietivists are talking about the temperature ‘anomaly’ they’re saying the next to last pixel on the right hand side of that graph is ‘normal’.and anything else is abnormal – man made catastrophic climate change. They’re just ridiculous.


Sorry – I mean the 450 000 year graph – doh


On the timing of the interglacials and the MPR (mid pleistocene rerevolution) there is an interesting paper by Maslin and Ridgewell 2005:
They question the orthodoxy that the post-MPR timing is eccentricity driven. They are not however questioning Milankovich forcing in general – they suggest that post MPR timing is actually with precession – every 4 or 5 cycles, but “paced” or entrained by eccentricity.
For me this would seem to point to weak forcing of a nonlinear oscillator where the relation between frequency of periodic forcing(s) and the emergent frequency is complex. It is possible in fact that the MPR could just represent a transition between strong (obliquity) and weak (precession plus eccentricity) periodic nonlinear forcing.
This would make srnse in the context of the gradually deepening glaciation and increasing “difficulty” in the starting of interglacials. Note yhat our current one – the Holocene – had a false start, the YD.
If the trend in deepening glaciation continues then interglacials would stop at some point. The Holocene could even be the last one. Thiscpuld be just the start of a deep glaciation aapproaching “snowball earth” such as the Saharan-Andean (end Ordovician) or the earlier preCambrian Cryogenian glaciations (e.g. Sturtian, Marinoan-Varanger).
It would be interesting to find out whether these earlier major glaciations were also preceded by an initial phase punctuated by interglacials – does anyone have any information about this?


I have a couple of problems with this. Forced harmonic oscillators have several essential components: A restoring force (approximately linear, at least for small perturbations). A driving/forcing force — usually harmonic, if only because we have to do nasty convolutions if it is not. A damping force to represent dissipation, (usually approximately linear in the velocity). And a mass.
I realize that you are expressing a metaphor, not asserting a model, but I’m not sure that a metaphor justifies extended conclusions as if it were a model. In particular, I can see nothing in a climate system that performs the same role as a mass (or inductance, if you prefer electric circuit oscillators). Yes, there is an internal storage or buffering of energy in e.g. the deep oceans, but that energy has no momentum equivalent and cannot carry the system through even a single undamped, unforced oscillation if it is perturbed.
I should qualify this statement, of course. The weather involves secular motion of actual mass on the Earth’s surface — atmospheric flow, thermohaline circulation — that have actual momentum and which are forced by a complex mix of Coriolis pseudoforces and real variable buoyancy forces as it is differentially heated and cooled, and some of those motions have natural rotational periods and a very few — e.g. the evolution of the diurnal tidal bulge — could have something like an actual restoring force coupled to a periodic forcing. However, the frequency spectrum of the mass/momentum oscillations of this sort is highly compact compared to even the smallest frequencies relevant to climate evolution on geological time scales — they are simply irrelevant, or at least, it is very difficult to see how they could be relevant.
On the longer timescales, I think you have to think of everything changing very, very slowly — slowly enough that the system for the most part merely tracks a local “quasi-equilbrium” dictated by things like the orbital dynamics, which at least have a very definite and computable effect on insolation as eccentricity changes. It is much more difficult — for me, at least — to understand the effects of changes in obliquity and precession, as they involve the projection of varying insolation onto the also slowly varying geographical arrangement of continents and oceans. This is further complicated by a secondary but extremely significant variation in planetary albedo with the distributed fraction of planetary surface covered with snow and ice, which is also effectively projected onto the slowly varying geographical arrangement of continents, sea bottoms, mountain location and height, and coupled to things like thermohaline circulation in nontrivial ways, and the fact that the dynamics themselves are highly non-Markovian with a time kernel or “memory” of previous climate with timescales that can be very long indeed — hundreds of thousands of years in the case of Antarctic and Greenland ice pack and (perhaps) the deep ocean.
The closing of Panama and subsequent rearrangement of thermohaline circulation, if indeed this was the proximate cause of the Pleistocene’s gradually deepening descent into glaciation, is then very “odd”. If this “flipped a (million year long) switch” as of maybe 1.9-2 mya, with a gradually increasing effect up to that point, one would expect to see some sort of disjunction in the global temperature, but in fact it smoothly continues the 41 ky cycle that was already established. Again, the interesting thing isn’t the 41 ky cycle — that is understandable — it is the continuing gradual deepening of the cold. The cycles, on average, keep getting colder and colder.
This is enormously odd. The average temperature of the planet is systematically changing, but by “average”, I mean in a running window maybe 200,000 years long to start to smooth out the cycle! The character of the oscillations is distinct — warm and cold phase temperatures differ by only 2-3 C, often less, and the Earth spends almost as much time a bit warmer than the mean as a bit colder. This behavior actually extends almost linearly back to an inflection point roughly 3.5 mya, but with what looks like chaos for the first 800,000 years — chaos with features tens to hundreds of thousands of years wide — before the 41 ky cycle asserts itself.
At 1.5 mya, the character of the oscillation changes again, but still within the 41 ky pattern — the oscillation remains roughly symmetric and if anything, it levels off for a half million years, but the amplitude of the oscillation roughly doubles to maybe 4 C with rare cycles as large as 6 C. At ~1 mya, it changes again, this time the most profound change seen anywhere in the last 5 million years. The cycle mean temperature substantially drops, by close to 2 C. The period converts to ~100 ky, but with lots of beats and stretches where the oscillation again looks more like chaos than a “simple” oscillator with a handful of relevant periods (it would be very interesting to do a fourier analysis here if one could actually include enough cycles to make it particularly meaningful, but really one can’t, I don’t think). The cycle peak to trough amplitude increases to as much as 8 or 9 C. And finally, the cycles become highly asymmetric, spending easily 90% of the time “cold or changing” compared to the time they spend warm. And finally, even though the warm cycles are comparatively short, even though the cold cycles are deep and long (long enough to build up 2-3 km thick ice pack on the continents!) the warmest part of the warm cycles warms up well past the peak temperatures seen in almost 3 my!
Oh my! How in the world can one understand this? Sure, it looks like orbital resonance and eccentricity became important but why only 1 mya? What was changing to (comparatively suddenly!) “switch” the system between the regimes discussed above? And what of the paradoxes inherent in the eccentricity even now, where perihelion occurs at the coldest, not the warmest time of the year. This is usually “explained” in terms of the differential albedo of land and sea and a north polar ocean vs a south polar continental ice cap, but all this explanation really teaches us — if true — is that the projection of the eccentricity, obliquity, and particular angle of season in the precession onto the exact shape of the continental land masses, smeared and modulated over thousand to ten thousand year periods by latent heat of any icepack and by the deep ocean temperature in places where thermohaline upwelling carries up deep water and by who knows how many other possible things? — is an extremely sensitive causal factor in progress towards or away from glaciation!
Literally, sweeping the precise angle of the equinox as projected onto eccentricity and the climate even a small amount can make a huge difference. It is very difficult to understand these changes in the pattern of glaciation in terms of the closing of Panama, as one would have expected that to have nearly been “equilibrated by hundreds of thermohaline turnovers even by the time it closed, or at least within 100 ky or so after.
This still ignores many factors that could be important. The annual variation of peak normal TOA insolation is roughly 91 W/m^2 (compared to the order unity W/m^2 forcing expected from doubling CO_2). A clear modulation of the climate occurs with what appears to be the period of an important decadal oscillation (the PDO). The state of the sun is fairly well known over the last 200 (instrumental) years, but is increasingly difficult to precisely infer or date from proxy data from earlier times. We are staggeringly ignorant about possible cosmological or solar modulators of climate, but there is substantial evidence that the climate system is amazingly sensitive to some small variations in forcing while perfectly happy to blithely ignore or even go counterphase to others, even when larger (e.g. the 91 W/m^2 variation). We do not even have a good feeling for the sign of the feedbacks for local short time climate dynamics and are cosmically clueless about longer time scales, e.g. the proximate cause of the Little Ice Age or Medieval Warm Period — none of this sort of century time scale variation seems connectable to Milankovich type long time scale dynamics, and yet the LIA “could” have been a trigger back into glaciation — as far as we can tell — or not — ditto. We don’t know why it happened in the first place, so we cannot say how important that cause is in the grand scheme of things over longer times.
Underlying this is the — IMO obvious — fact that the Earth’s climate system is fundamentally multistable, or at least has been for the last 3.5 my. Before that, there was a slight warming and cooling with fourier components that match up somewhat with obliquity and precession, but no discernible effect from eccentricity in spite of the fact that it should have been modulating as much then as it does now — presumably onto a world with the wrong continental shape and thermohaline circulation to support much oscillation from either that or obliquity and precession. (Even then, the climate appeared to be slowly cooling, but the effect is barely resolvable over millions of years.) Now, multistable with hysteresis, not with mass. It doesn’t seem to switch like an oscillator, it switches more (indeed, very much) like optical bistability in an open resonance fluorescence system, or (less) like a ferromagnet can be switched.
Multistable — lets stick with bistable for simplicity with just warm phase interglacial and cold phase glacial — systems have, for a wide range of their driving parameters, the possibility of being in either phase, with an imprecise boundary in parameter space within which they are locally stable. That is precisely what the data seem to suggest (for a value of multi greater than bi, possibly even for some sort of fractal distribution of possible attractors/stable points in the climate system). Once the Earth is glaciated, it is not at all easy to warm it up. Just the right conditions have to persist for a very long time to melt all of the ice, alter the albedo, restabilize in a warm phase interglacial. Once those conditions cease to hold, though, the system may well remain interglacial for a long time, even though if the earth were glaciated, it would remain so. This negative (cooling) feedback from ice is very likely to be why the 41 ky cycle is almost completely suppressed for the last my. Every four precessions (or so) obliquity, precession angle, the continents, and eccentricity all conspire to create conditions that can flip the switch, and once the switch is flipped they persist long enough to make the warm phase stable, but after a comparatively short time, precession makes it only locally stable — if it were cold, it would remain cold. The system then awaits a fluctuation like the LIA sufficiently long to “tip” it into the stable cold phase.
It might not need to be very long. If glaciers grow every year, you gain a tiny bit of albedo every year, as well as gain the ability to absorb a bit more insolation into latent heat (remelting of ice, evaporating of water) instead of reheating the air and ground to maintain the average. The same is likely true of icecap/sea ice modulation. Even things like mere “normal” climate variability can, in its drunkard’s walk, sometimes by pure chance create persistent heating or cooling because the system is so very nonlinear and multivariate.
The system is very likely crazy nonlinear chaotic enough that increasing atmospheric CO_2, which will very definitely tweak one of many climate forcings in a particular way, could very well cause a transition into the cold phase if the range of parametric stability of the warm phase has narrowed enough due to e.g. orbital precession from the warm phase initiator state of 12,000 years ago. If you study limit cycles of nonlinear systems at all you learn very quickly that as poincare trajectories are being followed around stable points in the dynamical evolution, perturbing the parameters away from stability in any direction will, in time, produce extreme-r behavior in the opposite direction as one shifts to a “larger orbit”. If there are multiple attractors, one can easily be pushed over the boundary and into the well of another attractor.
We don’t — I argue — know anywhere nearly enough to predict the effect of increasing CO_2 on the climate. One of many possibilities is to stabilize the warm phase and put an end to the glacial cycle for the time being, possibly even for geological time (as we don’t really know things like how far the continents have to move before the system stabilizes or destabilizes even more, possibly “suddenly” as in new modes appear). One theory for the Younger Dryas is a bolus of freshwater glacial melt suddenly dumped into the ocean interrupting thermohaline circulation long enough for glaciation to recur for a thousand year before orbital dynamics forced the system back into warming, but that’s only one of several possibilities. Assuming that the seas rise, we don’t know the feedback from sea level rise — does a greater sea surface area actually inhibit warming, so that it is self-limiting? Or does it increase warming, so that it tends to rise faster? Or both, plus other nonlinear effects from ice/albedo/latent heat modulation? Can we even say which one is likely to be dominant, let alone “certain” to be dominant? I doubt it.
I also doubt that we understand the even more subtle feedbacks of water vapor/cloud dynamics well enough to answer the question. There is a very good reason to think that the normal state of the climate equilibrium is the fixed point where water vapor feedback turns negative. That is, less (average) water vapor in the atmosphere causes warming to restore it, more (average) water vapor in the atmosphere causes cooling to restore it. That’s what stable equilibrium is — a point where small perturbations cause the system to return to equilibrium, not be forced further away. But if this assertion is true, warming from increased CO_2 should cause strictly negative feedback from water vapor and the water cycle to reduce the warming. If it is not true, one has to appeal to some subtle and complex things to explain why the climate doesn’t run away from positive feedback from water vapor alone.
Finally, “anthropogenic” contributions to climate variation are not limited to increased atmospheric CO_2 from human operated power plants. Every time an old growth tree in the rainforest is felled, we alter the biodynamic carbon cycle. It is further modulated by the rate that various nutrients are released into the ocean. The ocean itself has optical thermal properties that may well depend on things like pollution and silt from human farming and fouling of waterways. I’ve been in an extended discussion with somebody who thought that a lipid near-monolayer resulting from oil and gasoline dropped into the ocean by human boats and human garbage dumped in the ocean and oil leaking into the ocean etc is a major modulator of the ocean’s climate contribution — affecting things like evaporation rates and surface absorption of energy. I doubt he is correct, but I’d have a difficult time proving it from known data or previously done experiments. Farmland has a different albedo and very different climate impact in lots of ways than forest it replaces, and farmland in much of the world is at far greater risk of desertification, which has hysteresis associated with it — once a desert is formed, it takes a long time and just the right conditions to turn it back into non-desert land.
All things being equal, it would be lovely not to rock the Planet Earth boat too much as we struggle to build an equitable global civilization where the world’s 1/3 poorest people might as well be living in the 19th century or even earlier for all of the fruits of civilization that they can afford or enjoy. OTOH, it is unthinkable that we should — given our enormous ignorance of the effect of any given human activity — condemn millions if not billions of humans to perpetual poverty and misery and famine while we ourselves remain energy-wealthy, just because some models that appear to be actively failing predict a possible, but far, far from proven catastrophe. We simply don’t know enough to predict much of anything at all. If we could afford to leave things unchanged it would be great, but we can’t, and we don’t even know how to predict the future outcome of leaving things unchanged — it might be even more negative.
To conclude, I have to say that I doubt that we have an understanding of climate evolution sufficient, even with Milankovich and help from things he ignored, to take the Earth’s climate system in the Miocene and evolve it through the Pleistocene and into and through the Holocene right up to the human-forced present in the last century, at most, of the Holocene. Until we can, I would argue that we don’t really fully understand the climate, not to the extent required to make quantitative predictions or even to be able to resolve something very simple, like “the measured temperature distribution of Earth” vs “what the temperature distribution of Earth would have been if CO_2 remained flat at 290 ppm”. We don’t even know how to compute a statistical expectation for the delta in any way that is at all convincing, unless one is willing to conclude that our current climate is extremely unlikely because it isn’t doing what the climate models say it (probably) should, rather inverting the general course of science relative to model building.


Reading your comments has been more informative and thought provoking then reading the study that inspired this thread. How do manage to write so much, so well, and so fast?



After the initiation of extensive Antarctic glaciation at the Eocene/Oligocene boundary, with the formation of deep oceanic channels between South America and Australia on the north and Antarctica on the south, the Miocene showed major fluctuations in ice sheet extent there.
The Pleistocene can be viewed as the extension of the Cenozoic Ice House to the Northern Hemisphere. What the future holds, no one can say, but IMO the development of permanent continental ice sheets in the NH over millions of years cannot be ruled out. They might already exist if the North Pole weren’t at sea level instead of high elevation over land, like the South Pole.

Ah shucks…If we would get off our butts and start settling other worlds…This argument will be as dead as “T” REX….Would solve a lot of other problems too! Russia could go north into the UNIVERSE, and we could go south into the UNIVERSE…MUSLIM killers EAST into the same and Christians West into the same…Praying that all shall never meet again…MAYBE..But I F%$&^@G doubt it….HOMO SAPIENS just aren’t that smart…They rather kill all of us…Than live in peace and solve the worlds and our own problems as a species…..But at least there are still those who strive for the TRUTH…and for that….I GIVE all of you (with a minority of exceptions)…HUGE “A” for trying …I just hope there will be another “GRAPH” to read in another 50,000 or 100,000 years…Hope your listening God….


Wow – stunning, illuminating reply, thanks. I’ll try to digest it in due course, a few comments in response.
It has indeed been commented e.g. by Maslin and Ridgewell that it is odd how a forcing as weak and with such smooth oscillations as eccentricity can pace the interglacials. Not only that, but it seems that eccentricity forces interglacials MORE effectively at its low amplitude nodes (hardly any variation) e.g. now, 400 kya, 800 kya, than at the high amplitude eccentricity nodes (200 kya, 600 kya) at which the interglacials seem unstable and double-headed.
This huge sensitivity to small variations makes me suspect we will have to look to the physics / maths of weakly forced nonlinear oscillators. I take your point about “mass” or intertia. Maybe something like sea-level and its slow geological response to glacial-interglacial transitions could supply this.
Something maybe a bit like this:
About the glacial meltwater pulse and the YD – I commented on a recent YD thread that this seems to have happened at the Antarctic, a big collapse about 14000 ya dumped a lot of meltwater into the ocean system that kickstarted the Atlantic Meridional Overturning Circulation and caused the Bolling-Allerod warming. The paper I looked at was:
However to emphasis the daunting complexity of the system, ongoing deep ocean circulation effects of this Antarctic collapse also caused the end of the BA and the start of the YD a couple of thousand years later. This is in the context of – as you point out – the increasing amplitude of the glacial to interglacial oscillations.
What indeed does this mean? Something similar is happening with the Arctic annual ice extent in the last decade – bigger swings in extent from summer to winter – although this is associated with warming, not cooling. But being a believer in fractals, what you see on one scale can be also seen on another.


September 3, 2014 at 10:23 am
September 3, 2014 at 12:59 pm
The above was a reply to your long comment, sorry I posted it as a new entry rather than reply, need to get used to the new WordPress system.


Wow, that’s very interesting. I hadn’t noticed the similarity between sea ice extent and the 5 million year temperature record, but the resemblance is striking.
I still take issue with the “mass” issue. I see no way for any sort of thermal process to provide the analogue of “momentum”, certainly not on long time scales. To pursue the metaphor in the context of circuits, where “capacity” of charge is in some ways similar to “capacity” for heat/internal energy retention, the energy supply to the system may well have substantial variation, some of it highly periodic and functionally organized. The system itself is not a single reservoir/capacitor, it is doubtless multiple capacitors. These analogs are pretty faithful. The notion of resistance is straightforward — the climate system is dissipative — gain comes in from the Sun, is delivered (subject to noise and various internal feedbacks that regulate it in various ways) to the different reservoirs, and bleeds out to “ground” (the 3K Universe) from the various reservoirs through variable resistive pathways through one another but ultimately to ground. Average temperature is what happens as ins roughly balance outs, within the lifetime(s) of secular variations on the ins.
Nowhere in this dissipative circuit is there any analog of inductance, something that will cause the Earth to actually keep warming when its input is diminished, or cool when it is augmented, especially on a very long timescale, except nonlinear feedbacks in the system.
Systems with nonlinear, amplified, lagged feedback are perfectly capable of oscillating, but their oscillation isn’t that of a driven oscillator either mechanical or electrical. It’s more like the repetitive pattern of eddies that can occur in a rising stream of smoke from a piece of incense, or the turnover time of convective rolls in a bottom-heated pan of water. Fourier components can appear in a time spectral decomposition of a nonlinear system without that system really being in any way like a harmonic oscillator, damped, driven, whatever. The venerable “fox rabbit” (predator/prey, Lotka-Volterra) equations are a perfect example of nonlinear feedback leading to oscillation without either a mass term or a proper restoring force. I’d argue that predator-prey is a much better metaphor for the climate system than any sort of linear or nonlinear oscillator.


I don’t know if it qualifies as mass or momentum but the two hemispheres often juggle heat between them in a process called the bipolar seesaw. For instance events in the Antarctic – particularly an ice sheey collapse, initiated in the NH the BA and the YD at the inception of the Holcene.
Another ingredient for nonlinear oscillation is positive feedback, sometimes referred to as a “reactive medium” as in the case of the Belousov-Zhabotinsky chemical oscillator. The Bjerknes positive feedback between trade winds and Peruvian upwelling is the motor of ENSO. On a longer timescale there is a positive feedback in the Atlantic Meridional Overturning Circulation, whereby the North Atlantic drift brings highly saline water to the Arctic increasing the density of the cooled water so that sinks to form bottom water, in turn impelling the North Atlantic drift further.
This is why when you compare temperature history of NH and SH the latter changes smoothly while the NH switches abruptly between warmer and cooler periods – which become fiscreet and are given names such as the YD. Due to this salinity-downwelling feedback the AMOC becomes a nonlinear oscillator like the BZ reaction or ENSO.


When I say “nonlinear oscillator” I dont really mean like a spring or pendulum, but a system which intermittently becomes oscillatory or briefly takes on a life of its own. Not very precise terminology I admit.


There is a very good reason to think that the normal state of the climate equilibrium is the fixed point where water vapor feedback turns negative. That is, less (average) water vapor in the atmosphere causes warming to restore it, more (average) water vapor in the atmosphere causes cooling to restore it. That’s what stable equilibrium is — a point where small perturbations cause the system to return to equilibrium, not be forced further away. But if this assertion is true, warming from increased CO_2 should cause strictly negative feedback from water vapor and the water cycle to reduce the warming. If it is not true, one has to appeal to some subtle and complex things to explain why the climate doesn’t run away from positive feedback from water vapor alone.
I just had time to read the whole of your first comment (unlike you I’m quite slow at reading and writing with a touch of dyxlexia in my early years – probably still). For me this is the best general overview of our knowledge of climate that I have read since it comes at it from the right angle – involving nonlinear dynamics at the core, not just giving lip service to the same. What a refreshing contrast for instance to the sterile linear approach of – for instance – Gavin Schmidt – for whom climate is a static system at equilibrium with the ocean a passive puddle, the whole system only forceable from the outside. (Gavin is a very bright guy but locked in a dysfunctional paradigm like all the great mathematicians who worked for centuries on orbital epicycles.)
The above quote about climate equilibrium (intermittently changing equilibrium in the Lorenz sense, not permanent equilibrium in the Schmidt sense) may – if I am not wrong – represent also the Ferenz Miskolczi theorem. For all that we know and – more importantly – don’t know, there is a strong likelihood of the whole CAGW story being entirely wrong or even opposite of reality.
You should consider writing a text book with a title like “The cloud of unknowing – the nonlinear-chaotic dynamics of climate”. It could for instance follow the concept of Dawkins’ “Ancestors’ Tale” in having a chronological sequence, not from present to past or vice versa, but from long to short timescales. One could start from billion year to multi-million year timescales, then down to the recent glacial period (hundreds of thousands of years) and eventually to the subannual scale of weather. The unifying theme would be nonlinear dynamics where the same recognizable patterns would keep on showing up, illustrating fractality.
I cant think of a better person to write such a book than yourself (flattery gets you everywhere!). Such a book would be an essential starting point for study of climate to restrain the hubris on the subject which pervades current climate narrative. Your above post would be a significant fraction of one of the chapters.
I agree BTW with your comments about human affects on climate beyond CO2. Here at WUWT we should not convey the impression that we are complacent about any deleterious effects of human activity on the earth’s climate and ecosystem, your comments in this regard will I’m sure find agreement from many here.


Write (another) book? Perhaps if any of my companies make a gazillion dollars for me. In the meantime, I must work for my meat and at the moment taking on ONE MORE PROJECT would be enough to put me right over the edge. The other problem with writing such a book is the same problem that plagues science in general. Nobody wants to read about null results. Showing that oatmeal is no better for you than steak as far as end-stage morbidity and mortality (if true) is not a popular conclusion with those that wish to believe otherwise. Margarine vs butter. Eggs vs an egg-free diet. Alcohol is bad vs alcohol in moderation is good vs no whoops it’s bad after all — nobody will admit that a) in many cases the marginal risk is tiny, and strongly controlled by other variables such as personal genetics and life-style so that even if it is true in one sub-population it is false or irrelevant in another; b) that small margins in highly multivariate problems do not lead one to a great deal of certainty, that in many, perhaps most cases in situations like this we don’t really know is the “right” answer.
It’s not just climate science, in other words. It is everywhere in science. Research physicians and biologists who can’t get funding and tenure for null results in medical science. Climate scientists who can’t get funding and tenure for null, non-catastrophic results in climate science. Physicists who probably won’t get funding and tenure if they elect to join the tiny number of physicists who are already pursuing the elusive chimerae of the field, e.g. magnetic monopoles. A few funded monopole traps is plenty — there just isn’t any point in running any more, which makes it a dead end for graduate students unless they come out able to work on something else, somewhere else. Or, of course, unless they find a reproducible monopole signature at 5 sigma in the 4 to 6 years they are likely to have running the apparatus for the PI.
The problem is rampant in the social sciences — studies have shown that it is far worse than in the hard sciences. If one is funded to do a study to see if being raised in a poor neighborhood makes it more likely that you will grow up with a twitch in your left eye, you’ll find some way to dredge the data to make it so rather than work for three years, get a completely null result on N=400 samples, and come back to request three more support to rule out a twitch in the right eye (and hope that you get tenure in the meantime).
The problem is reflected in the number of papers published that check other people’s work. The small number. Many papers are published, unchallenged, and the essential step of validation by an independent researcher (possibly working with independent methodology) is skipped, so that the unchallenged results move directly into the compendium of supposedly revealed truth in the field until, years later, somebody notices that they make no sense and finally get around to (maybe) falsifying them, if they can get the support to do so. And whenever real money is on the line — for example when considering the virtue of drugs that cost a half-billion dollars to develop and patent and gear up to manufacture on a large scale — companies are really crossing fingers that if anything does turn up to refute the carefully selected results from the original trials, it does so after the company has recovered most of this investment if not made a profit.
That’s why Briggs’ site is so very, very amazingly amazing and useful. If I had to pin down a major flaw in modern education, it is that most of the introductory statistics courses — usually the only course on stats that science majors take if they take any at all (in many majors, they aren’t required to take even one) they have time to — at most — crudely cover things like linear regression, p-tests, t-tests, the central limit theorem, chi-squared, and maybe R-squared. By crudely I don’t mean to imply that the presentation isn’t correct and accurate — only that they are strongly limited by the mathematical competence of the students taking these courses (who are the same students I teach physics too — after and while teaching them what amounts to remedial math including algebra, calculus, geometry — pretty much everything). They exit with a handful of hammers in search of nails and very, very little conceptual understanding or common sense understanding of physics.
Briggs addresses this with simple minilectures and rants that reduce a lot of the concepts to stuff simple enough for anybody to understand so that they can understand why fitting linear trends to e.g. timeseries data is a process that will lead to far less reliable knowledge of the timeseries than you think it will if you just apply the stuff you learned fitting normally distributed data around an actual underlying linear process in stats class, and that is before you fall into the trap of picking end points that maximally bolster your desired argument, a.k.a. cherrypick the data because of your rampant case of confirmation bias or a desire/desperate need to get funded and hence continue to be able to eat and buy your children shoes and orthodontics instead of working as a Wal-Mart greeter.

johann wundersamer

@tty – referring to
rebound had time to go much
further than during other
interglacials. All sites where
such very high sea-levels have
been reported are either
tectonically unstable or within
the “forebulge” zone of the
Laurentide ice-sheet.’
yields to: some watermarks going up, others going down.
so – is there evidence of lower sealevels on discrete shores?
/didnt read that thread all way down yet; maybe this argument’s already done/
Regards -Hans