Ice Ages, Feedback Diagrams, and Climate Triggers

Kevin Kilty

Recently I got around to reading my May 2020 (yes, I am that far behind) issue of Physics Today. It contained what promised to be an engaging article on tying celestial mechanics to Earth’s ice ages.[1] Indeed, the article provides many interesting points between and among celestial mechanics, climate changes, and impacts on human populations and evolution. There were some concerns in my mind about some details the article presented, which I will discuss presently, but one statement the author made caught my attention specifically.

“Changes in GHGs always precede variations in global temperatures and are therefore a clear driving force of climate change, not a response to it.”[2]

This appears to fly completely in the face of what seems to me a general opinion expressed on WUWT – that CO2 in particular changes in response to changing global temperature, with CO2 rising with a 800 to many thousand year lag behind rising temperature.[3] There was but a single reference provided for support of Maslin’s claim, and I immediately obtained this article.[4]  Let’s examine this claim about relative timing of CO2 and temperature changes before moving on to the principal topics of this essay.

Does CO2 lag or lead temperature?

There are several things about this cited research that weaken its support for Maslin’s seemingly strong claim about timing between ice ages and CO2 fall or rise.

First, the supporting article title contains the phrase “during the last deglaciation” which restricts its findings to a period of time since the last glacial period and to smaller temperature and ice volume excursions. The physics of these processes could be quite different from the longer-term, and larger amplitude process of periodic global stadia and interstadials.

Second, the analysis in this supporting article focuses on Antarctic ice cores to the exclusion of Greenland ice core results. This exclusion is defended on the basis that the Atlantic Meridional overturning (AMOC) causes a seesawing of heat balance between the hemispheres, and thus the Greenland ice core results make a poor representation of global conditions.

Third, the premise of the article, that CO2 is the principal driver of climate change within the time period chosen for study is supported through a comparison of temperature proxies to CO2 concentrations against  EPICA dome C ice core. Yet, the authors spend much effort bolstering their claim through global climate modeling. I am always skeptical about modeling.  A careful inspection of the plot showing correlation between CO2 and the global temperature stack from proxies, shows only one sigma error bars (uncertainties) and leads to a better impression of CO2 leading temperature than what one might conclude for a 95% (nearly 2 sigma) confidence plot. The modeling support, which comes from 1000 Monte Carlo runs, suggests a global lag of temperature behind CO2 of 460 ± 340 years with a coverage factor of only one (1 sigma). Thus a 95% confidence interval would be consistent with zero lag or even a small negative lag.

Fourth, the temperature proxy data are biased well away from polar regions and the edge of the ice sheet where Maslin’s discussion mainly focuses on feedbacks involved. Moreover, many potential global influences on the climate system are poorly constrained (dust for example). The author admits that the changes in CO2, which levels off a millennium or more before temperature does, cannot be the sole driver of climate change. Temperature must be driven by “other aspects of the climate system”.[5] Liu, et al, come to  this same conclusion.[6]

I would say the claim put forth by Maslin has some support but is still weaker than he implies..  

A theory of growth of ice sheets

Let’s now leave the critiquing of Maslin’s claims regarding the relationship of CO2 variations to temperature, to examine more specifically his discussion about what causes ice ages to wax and wane. First, to initiate an ice age there is a pronounced decline of insolation at 65 degrees north latitude. This, he claims, must be the result of orbital variations. This reduced insolation allows snow from the previous cold season to remain over to the next, with an attendant accumulation of thicker snow year by year. This, in turn allows a foothold for an ice-albedo feedback to provide additional cooling of the climate and the accumulation of thicker ice sheets. Meanwhile the cooling climate results in declining levels of CO2 and water vapor in the global atmosphere which cools the climate further in a positive feedback loop.

Once ice sheets have grown to substantial thickness another feedback appears which is the ice sheets themselves pushing circum-global atmospheric circulation toward the tropics. This starves polar regions of precipitation. This negative feedback loop prevents a continually growing thickness of ice sheets and further drying of the atmosphere. It acts as a hard limit of sorts to the growth of ice sheets, and if one can compare the sum total of these processes as acting as a feedback regulator, this hard limit behaves like a relay in a refrigeration cycle — it opens to halt further cooling processes.

Over the past million years or so this process of insolation triggering a cascade of positive and negative feedback results in ice sheets growing to maximum thickness in about 80,000 years. Increasing isolation then triggers an escape from an ice age in about 20,000 years with growing greenhouse contributions from rising concentrations of CO2 and water vapor, and a greening of regions formerly covered with ice. Except for being more rapid, deglaciation appears the reverse process to falling into an ice age.

A different view of feedback

One way of supposedly clarifying climate change is to explain it using a feedback diagram. While not really providing any clarification, these diagrams are often exceptionally simple. Just to make sure I wasn’t misstating the peer-reviewed research, I tried to find such an original diagram in the two most often cited papers, Hansen et al 1984 and Schlesinger and Mitchell 1987.[8] Neither appears to contain such a diagram. Thus I created one from an equation provided in the 1987 paper, ΔTs = ΔRTG0/(1 – f). Figure 1 nearby shows exactly the diagram this equation describes.

Figure 1 Caption. A feedback diagram equivalent to Schlesinger and Mitchell’s 1987 feedback equation. To see this easily, start at the summation node and note that the summed signal is (ΔR + FΔT) which is multiplied by G0 to produce ΔT. Thus, G0(ΔR+FΔT)=ΔT. Let f=FG0 and then solve for ΔT. The result is ΔT = ΔRG0/(1 – f). It is also possible to make this diagram equivalent to a differential equation, but I digress.

I have always disliked using this particular feedback diagram to explain climate change for several reasons. First, the source of energy that makes the whole loop run is implied, which is fine for electronic circuits.  Any attempt to ground it in reality with, say, energy balance, which is crucially important in discussion of climate change, is simply hopeless. Second, the feedback diagram suggests it is a matter of simple multiplication of the various blocks in the loop, when in fact the process is multiplication in the “S” domain of Laplace transforms. To transform to a time domain description requires convolution of signals against impulse response. Neither view helps clarify matters for most people. The diagram obscures time constants involved of which there are at least two within the F block. Third, this diagram contains no non-linear element, suggesting it describes a linear system which climate surely is not.

The deficiencies of this diagram are probably at the root of many disagreements over its pertinence. Possibly, though, this simplified view encourages a more fundamental problem, which is to encourage use of gain and feedback parameters observed in parts of the control domain that are inappropriate to other portions of the control domain. In other words, it suggests that the control problem is independent of amplitude, which may be at the root of the most recent criticisms Monckton, et al, level.[9]

Maslin’s article set me upon constructing a feedback diagram which addresses two of my complaints – one that applies to disturbances as great as ice ages and may have pertinence to the problem of trigger points.

Earth temperature regulation

While the effect of increasing CO2 on present and short-term Earth temperature is commonly illustrated with a feedback diagram. I cannot say I have ever seen an attempt for the larger and greatly more complex problem of pleistocene temperature regulation. Can we consider this larger problem in terms of a feedback diagram like a temperature regulator, for example?

For guidance in this regard one might first look at the record of pleistocene ice volume, which displays the following pertinent features: 1) it shows turning points at well defined limits, and 2) it displays a periodicity that is the 40,000 year cycle of obliquity modulated by the 20,000 to 29,000 year cycle of precession of perihelion. It  clearly shows a limit-cycle having perhaps two periods both of which are subharmonics of the orbital influences.

As well defined turning points in response and a limit-cycle of operation are long established characteristics of relay control systems, I submit that Earth’s climate regulation is non-linear in much the way a relay controller in a regulator is non-linear. Figure 2 shows an appropriate modification to the simple feedback diagram of Figure 1.

Figure 2 Caption. A more realistic feedback diagram contains a non-linear element (N) which is a function of both the amplitude (A), and frequency (ω) of the feedback signal. All of the complexities of climate are meant to reside in block N, including changes in greenhouse gas concentration, while the function of the gain block (G0) is simply to take solar illumination (IS), including its disturbances due to orbital variation, and produce a mean Earth temperature (T), not just a small disturbance to it.

To buttress my claim, Table 1 shows some selected climate features that serve to function like a relay controller (see Figure 3), or something similar to a relay. By “something similar” I mean a softer relay with a characteristic like that in the lower part of Figure 3, or something even softer such as an ArcTangent function.

Table 1. Sources of relay-like limiting of climate excursions

Source MechanismLimiting at high temperature or small ice volumeLimiting at low temperature or large ice volume
Hydrological cycleExponentially increasing rate of hydrological cycle 
Atmospheric compositionDeclining unit influence of a growth of atmospheric CO2 along with a limit to moistening of the atmosphere.Increasing unit influence of a growth in CO2 along with a limit to continued drying of the atmosphere.
Albedo variationSW influence of deepening cloud coverInfluence of dustiness on ice albedo
Atmospheric dynamics Deflection of storm tracks

Since a person can itemize influences that limit temperature response, our system has the potential to behave like a system with a relay in it and the idea of treating it as a relay controller must have some merit. This climate relay opens to halt the effectiveness of influences tending to increase system response when the system is near its maximum; and reduce the effectiveness of influences making the Earth colder near the temperature minimum.

None of what I claim here is beyond what one could glean from a reading of the pages of WUWT from contributors such as Weekly Climate and Energy News Roundup (especially their recent summary in #482 of Professor Happer’s remarks at the Hillsdale College leadership seminar), Roy Spencer, Richard Lindzen, Willis Eschenbach, and many others too numerous to mention.

Figure 3 Caption. The hard response of an ideal relay in an Off-On control loop in the upper portion of the diagram. A softer version I call an “Ideal Earth Climate System” is seen in the lower part. One could construct even softer versions of the Earth temperature regulator, but the observations regarding ice ages suggest that however softly it may operate, the Earth has a limiting non-linear element of some type.

In contrast to linear control systems, there are fewer tools available for analysis of non-linear regulation. One technique is to produce successive linear approximations to construct the entire control domain. Each approximation over an infinitesimal portion of the response curve can yield information about system behavior after a small disturbance. Another method of analysis is a digital computer simulation tool. One older analytical tool used to handle non-linearity is the describing function approach. This approach requires a separate treatment for each harmonic (fourier component) of the signals circulating around the feedback loop, including the harmonics or subharmonics generated by the non-linear element.

Relay dominated regulators are known for operating in a limit cycle, and the describing function analysis will show this,[11] but the relay or relays involved in limiting the growth or shrinkage of continental ice don’t behave exactly like a relay providing temperature control for a furnace. A furnace heats a building when its relay closes while the heat losses stay constant. In this case of a “climate relay”, its closure switches off the further accumulation of ice and continued drying of the atmosphere, and maintains this limiting function while awaiting the signal from orbital parameters to begin the process of glaciation or de-glaciation. There may be no triggering points intrinsic to the N block, but there are variations of insolation input to allegedly serve this purpose.

Triggering events

Maslin credits the triggering of an ice age to orbital elements or celestial mechanics which adjusts insolation to a triggering value, just as Milankovitch’s original theory supposed. The many orbital elements involved are:

  • Eccentricity of Earth’s orbit which varies from nearly zero (a near perfect circle) to a maximum value of 0.057 in a 96,000 year-long period. This leads to differences of yearly insolation of nearly 12% over this period.
  • Obliquity, the angle of Earth’s axis with respect to the plane of its orbit varies from 21.8 to 24.4 degrees over a period of 41,000 years. This modulates the variation of insolation between the hemispheres, which is made even more pronounced because of the difference in proportion of land between the two hemispheres.
  • Precession which involves both the precession of the equinoxes and precession of perihelion. Between these two motions it takes a variable length of time (20,800 to 29,000 years) for the orbit to revolve once with respect to a fixed orientation such as the Vernal equinox. But this is not to say that insolation values repeat exactly over this same period because all the elements are varying over different periods.

Yet, these factors cannot fully explain the march of ice ages. One of the more interesting references in the Physics Today article was Huybers’s investigation of orbital elements initiating an escape from an ice age.[12] The insolation anomaly required to trigger an end to an ice age is not a precise value, but rather a random variable. Insolation anomalies at 65 north which fail to start the escape from an ice age are in a few cases larger than insolation values that initiate an escape. Using observed oxygen isotope values as a proxy for ice volume, and for global temperatures in turn, provided Huybers the raw material to build two distributions of insolation values that fail and succeed, respectively, through a resampling process.[13]  These two distributions (which are actually joint distributions of obliquity and precession) overlap substantially and provide only about ⅔ of the explanation for deglaciation — leading to a need for some additional factors contributing to ice age start and end.

The trigger may not be entirely a matter of orbital elements. For example, an usually long summer season over southern oceans might release a sizable fraction of greenhouse gasses that had been removed from the atmosphere in the earlier cooling cycle; or, maximum insolation operating on the upwelling deep water over tropical surface oceans might do the same. Perhaps internal dynamics of the coupled ocean and atmosphere contribute as well.


Whatever the answer turns out to be, a person cannot look at a plot of δ18O, such as Figure 3, here, and not be struck by two things; 1) a preponderance of triggers carrying the climate out of an ice age – none seem to work oppositely during its warm phase, and 2) the smaller range of ice-volume variation prior to 2.8 million years ago. In terms of the relay-control model of climate, whatever conditions pertain to this time period the relay had smaller dead-band and the limit cycles had smaller orbit. The climate was more stable. Maslin speaks of our creating a present day super interstadial. By this he means that through altering the atmosphere by burning fossil fuels we will have delayed a start to the next ice age from near the present time to perhaps 60,000 years in the future. A more stable climate. That, my friends, sounds like awfully good news.


1-Mark Maslin, Tying Celestial Mechanics to Earth’s Ice Ages, Physics Today, p.49-53, May 2020. For those readers interested in this, the article is open access for the remainder of year 2021 for people willing to register at AIP.

2-ibid. p. 51.

3-See for example Euan Mearns,

4-Jeremy D. Shakun, et al, Global Warming preceded by rising carbon dioxide concentration during the last deglaciation, Nature, Vol. 484, p 49-55, 5 April 2012. doi:10.1038/nature10915

5-ibid. p. 51.

6-Zhengyu Liu, et al, The Holocene Temperature Conundrum, PNAS, Published Online August 11, 2014. doi:10.1073/pnas.1407229111.

7-Hansen, J., A. Lacis, D. Rind, G. Russell, P. Stone, I. Fung, R. Ruedy, and J. Lerner, 1984: Climate sensitivity: Analysis of feedback mechanisms. In Climate Processes and Climate Sensitivity. J.E. Hansen and T. Takahashi, Eds., AGU Geophysical Monograph 29, Maurice Ewing Vol. 5. American Geophysical Union, pp. 130-163.

8-Michael E. Schlesinger,John F. B. Mitchell, Climate model simulations of the equilibrium climatic response to increased carbon dioxide. Reviews of Geophysics, 25, (4), 760-798. May 1987.



Note in particular an especially pertinent observation by Dave Fair followed by one from Beng135

11-Charles Phillips and Royce Harbor, Feedback Control Systems, 4th Ed., Prentice-Hall, 2000. Or, Otto Smith, Control Systems Engineering, McGraw-Hill, 1958.

12-P. Huybers, Combined obliquity and precession pacing of late Pleistocene deglaciations, Nature, 480, 229, (2011). doi:10.1038/nature10626

13-For those unfamiliar with resampling, a great reference complete with exercises is, “Resampling: The new statistics, Julian Simon, 1997.” The publisher appears to be Professor Simon himself. 

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John Tillman
December 8, 2021 6:27 am

I respect and have communicated with Dr. Maslin in the now distant past. However, he’s clearly wrong about CO2’s leading changes in temperature. Present academic orthodoxy might have necessitated his genuflecting in passing toward the Great God CACA.

The quickest and easiest way to falsify this hypothesis is to observe that deglaciation begins precisely when CO2 is at its lowest, as at the end of the Last Glacial Maximum.

His discussion of high latitude insolation and the feedback effects of albedo and on atmospheric circulation explain ice sheet formation and termination, without resort to CO2 increase, which results from climate change, but doesn’t cause it, except as a minor feedback itself, above the minimum required to support photosynthesis in most plants.

Reply to  John Tillman
December 8, 2021 7:43 am

Yes.Maslin is wrong. The first thing I did when I started investigating climate science was to replicate the correlation analysis on the ice cores using a different method. The Vostok data shows about an 800 year lag, but DomeC, which is a higher resolution core analyzed with more modern methods and equipment shows a delay of about 200 years and I believe this to be more correct than the 800 year delay in Vostok cores.

The 200 year value is consistent with the time it takes for forests to take over where it used to be ice and the existence of more biomass requires more CO2 to be in the system, and visa-versa.

John Tillman
Reply to  co2isnotevil
December 8, 2021 8:19 am

Dr. Maslin does believe that humans will delay onset of the next ice age:

In which case our CO2 release is a good thing.

Reply to  co2isnotevil
December 9, 2021 2:51 pm

“Meanwhile the cooling climate results in declining levels of CO2…” So, temperature leads CO2 concentration on the way down but not on the way up?

Reply to  John Tillman
December 8, 2021 8:25 am

I have recently discovered Ralph Ellis on youtube. He is a prolific author and researcher. He has a published a peer-reviewed paper on ice ages (that he proudly points out has been downloaded more than 20,000 times) which is a must read item. Also he has provided several excellent lectures on the subject in his youtube channel. The feedback loops above are partly involved but the important aspect of albedo appears to be missing.

John Tillman
Reply to  ReaderX
December 8, 2021 8:41 am

It’s not missing. Maslin includes the effect of dustiness on albedo.

IMO, Ellis overemphasizes that feedback. I also disagree that precession is the most important Milankovitch cycle. IMO, it’s obliquity (tilt), modulated by the other cycles and in the longer term by tectonics and solar output.

Ellis and Palmer, 2016:

Modulation of ice ages via precession and dust-albedo feedbacks

Gary Pearse
Reply to  John Tillman
December 8, 2021 4:31 pm

Surely, the greatly reduced atmospheric CO2 (180ppm) by the time of the glacial max
must be in equilibrium with its greater content in what was an increasingly colder ocean where it became sequestered.

As you point out John, the orbital driver of the glacial max simply reverses, solar insolation increases and the ocean then outgasses, restoring the atmosphere’s CO2. The increase of atmospheric CO2 is, in turn, buffered by absorption into new plant growth giving a three-way equilibrium among ocean, atmosphere and biosphere.

This is a simple model that climate science must have done something with.

Reply to  Gary Pearse
December 9, 2021 3:15 am

At the 180ppm levels, increasing CO2 has a significant “greenhouse” impact…and likely sets up a significant warming feedback loop that diminishes to insignificance as concentrations approach the 275ppm level…where the (CO2 concentration variable) Equilibrium Climate Sensitivity becomes an insignificant driver within the feedback loop.

Bob Weber(@coolclimateinfo)
December 8, 2021 6:27 am

The modeling support, which comes from 1000 Monte Carlo runs, suggests a global lag of temperature behind CO2 of 460 ± 340 years with a coverage factor of only one (1 sigma). Thus a 95% confidence interval would be consistent with zero lag or even a small negative lag.”

Who is teaching these idiots? It took me one run to find CO2 lags T by 400-600 years.
comment image

Reply to  Bob Weber
December 8, 2021 8:51 am

In short, Maslin is lying.

To bed B
Reply to  Graemethecat
December 8, 2021 10:29 am

Maybe just a hockey-stick stunt where data consistent with what you want to see gets weighted.

Reply to  Bob Weber
December 9, 2021 2:11 pm

Difference between reality and alleged models.

Ron Long
December 8, 2021 6:33 am

Great review by Kevin. The glacial/interglacial intervals we find ourselves in, collectively an Ice Age, seems to demand some very large scale cycles controls, hence the variations of the Milankovich theory. However, the regularity is (spectacularly) interrupted by events such as The Younger Dryas or the Little Ice Age, which possibly is the climate variations that Kevin is talking about re feedbacks and forcings. I wonder if some enterprising geologist might factor Continental Drift into the climate variations? If the atmospheric CO2 content can stall of the next Glacial Cycle I will drive my SUV around some more.

John Tillman
Reply to  Ron Long
December 8, 2021 6:58 am

Cold snaps during glacial terminations, like the YD, also show that CO2 isn’t the control knob on climate change. The YD and other such rapid coolings, occur after warm intervals (DansgaardOeschger Events), during which CO2 rises.

Likewise, Heinrich Events, sudden coolings during glaciations caused by iceberg armadas, happen after warmings, ie interstadials.

IMO there isn’t enough fossil fuel left to ward off the next glaciation.

Peter Wells
Reply to  John Tillman
December 8, 2021 7:28 am

At least additional CO2 will help plant growth, which becomes more of a problem as the growing time is reduced by the oncoming ice age.

John Tillman
Reply to  Peter Wells
December 8, 2021 8:04 am

At present rates of use and liable pricing changes as supplies become costlier to recover, a reasonable estimate for fossil fuel reserves is 600 years. The next glaciation won’t start that soon, or even by the time the extra plant food has left the air.

We might have fusion energy before economically recoverable reserves are mined. With abundant, cheap power, we could keep ice sheets from forming by melting snow still left at the end of summer in the regions in which they build up.

Reply to  John Tillman
December 8, 2021 8:48 am

Should we figure out a way of mining methane hydrates we could have thousands of years of fuel available.

John Tillman
Reply to  mkelly
December 8, 2021 10:18 am

Estimates of total reserves have dropped every decade since the discovery of CH4 clathrates. Today the range is a factor of five, with the low end about twice current economically exploitable conventional gas reserves.

So dunno if thousands of years, but at least hundreds, if feasible. Might be more lurking in Antarctic waters than now guessed, as well.

Komerade Cube
Reply to  John Tillman
December 8, 2021 9:18 pm

>>We might have fusion energy << only ten years away!

Ron Long
Reply to  John Tillman
December 8, 2021 9:24 am

John, I was just watching the History Channel “Secrets hidden in the ice”, and here’s an alert about warding off the next glaciation: Part of the DEW (Distant Early Warning, powerful radars) ended in Greenland. The stations there were built on buried frames which allow jacking up the module if needed, to avoid being buried in the snow accumulation. DEW was around 1950 to 1990, and in that 40 years the DEW module was jacked up a total of 104 feet. If this is what we get in this inter-glacial, what is a glacial event like? Quick, everyone into your SUV’s.

John Tillman
Reply to  Ron Long
December 8, 2021 10:08 am

Also structures in Antarctica have been buried by ice.

Reply to  John Tillman
December 9, 2021 9:54 am

IMO there isn’t enough fossil fuel left to ward off the next glaciation.

Agree, the 1000 yr or so expiration date for fossil fuels is a blip on the glaciation cycle timeline. Maybe we’ll have nuke-powered limestone-cookers going by that time to continue the CO2-enrichment….

Last edited 1 month ago by beng135
Kevin kilty
Reply to  Ron Long
December 8, 2021 10:10 am

Good point, Ron. If you look at the ice volume proxy from the pliocene to present you notice a constant growth in ice volume upon which there are small deviations. These small deviations then become large deviations in the pleistocene. I suspect, and I think I have even read this in the literature long ago, that the growth of tall mountain ranges recently in geological time has dried the atmosphere, making increasingly large regions where IR radiation is far more effective in cooling the planet as it is possible to nearly cool the surface directly. There is an effect of global tectonics for you perhaps.

Kevin kilty
Reply to  Ron Long
December 8, 2021 11:41 am

Ron, Have a reading of the reply John Tillman sent to me down thread a ways. It is a very good example of plate tectonics’s influence on tertiary climate.

Reply to  Ron Long
December 8, 2021 12:48 pm

It seems at best very difficult to either eliminate or quantify the possibility that elements from outside the Earth, even outside the solar system, have had significant influences on long term climate. For one example, sunspot counts are a proxy for solar output, not a measure if of it. For another, claims that variations in gravitational interactions are too small to make any difference are a belief, not an established fact.

Carlo, Monte
December 8, 2021 7:27 am

The point about Laplace transforms is absolutely correct, the equations only become simple multiplications of the nonlinear elements in the frequency domain (s domain, the complex frequency variable). In the time time domain the equations have to be solved with convolution.

One point with gain blocks that isn’t visible in feedback block diagrams: they have to operate in their linear gain region so that output = input * gain. This requires biasing networks that are not shown or hidden inside, especially operational amplifiers. When forced outside of the linear region, which can happen for many reasons, they cease being multiplier blocks and become more like relays in some cases (“hit the rails”), or oscillating wildly.

Clyde Spencer
Reply to  Carlo, Monte
December 8, 2021 12:01 pm
Carlo, Monte
Reply to  Clyde Spencer
December 8, 2021 12:54 pm

A pity some of these AGW types haven’t learned anything from Monsieurs Fourier and Laplace.

David Stone CEng
Reply to  Carlo, Monte
December 9, 2021 4:02 am

There is another important point about these alleged diagrams, and that is that the gain of the amplifier should be effectively infinite, but the gain of the system is entirely controlled by the feedback network. This is very important as using an amplifier with a low gain factor completely wrecks the operation of the alleged “feedback” network accuracy at controlling the output. It is quite wrong to draw this diagram and attempt to separate the “gain” from the feedback network, although climate people always do this. What we need to see is the bode plot of the alleged transfer function of the system, which will include the delay (phase) of the various controlling parameters. Monkton’s paper tries to do this and results in a feedback “gain” of essentially 1 using actual measured data. It also needs to be realised that any attempt at a “positive” feedback will probably result in a wildly unstable system, although this may take a long time to develop because of the feedback network time constants, which for climate may be hundreds of years. The “positive” feedback crowd have had far too much notice taken of them because their models must be theoretically unstable (in other words a change in output results in a new larger change in output, ie. very non-linear) without any attempt to define the limiting conditions or the underlying time constants. This is entirely due to using digital computer models whilst not understanding the effects of time constants in all the parameters.

Jim Gorman
Reply to  David Stone CEng
December 9, 2021 6:00 am

Great analysis!

“What we need to see is the bode plot of the alleged transfer function of the system, which will include the delay (phase) of the various controlling parameters.”

This is why time series analysis is important rather than simple linear trends and seeing what correlates. This will be complicated because of varying periods and phases amongst the various variable cycles. It is almost to be sure to meet the IPCC statement about not being able to “predict” non-linear coupled climate.

Rich Lentz(@usurbrain)
Reply to  David Stone CEng
December 9, 2021 6:33 pm

@David & @ Jim;

This seems like what I was taught some fifty years ago in my senior year of a Vacuum Tube Amplifier design course. I also seem to remember that when working with multiple feedbacks that if the feedback opposite the predominate was less than 1/10 the value of the predominate feedback you could ignore it in your design calculations. There was specific emphasis on the fact that the phase of the feedback was very important to these calculations. In other words a phase shift of the signal can actually be the Negative feedback or the phase shift could cause a positive feedback and provide an actual gain in the signal – Like the Regenerative amplifier radio aI built as a kid.

The Positive and negative feedback and Lead and Lag of these feedbacks just does not jive with what I did in designing Control Systems for coal and nuclear power plants and while tuning them to operate properly and provide the necessary feedwater flow rates to keep the steam generators at the correct level.

Isn’t the negative feedback from water vapor 20 times larger than the positive feedback of CO2? If so what is all the fuss about CO2 for?

P.S. It has been over 50 years and I may be confusing Amplifier feedbacks with Control system feedbacks. But they sure seemed the same to me at the time. At least I treated them the same. Control systems were just slower than audio systems, much slower. And when tuned improperly oscillated just like a poorly designed amplifier. Actually happened to me during start up of a newly designed system once.

December 8, 2021 7:36 am


Your ‘more realistic’ feedback diagram is also incorrect. The issue is that it fails to accommodate the preconditions for applying feedbacik analyss. First is the missing implicit power supply whose purpose is to avoid having to apply COE between the input and output of the network. Second is the requirement for strict linearity. Approximate linearity between W/m^2 and temperature is insufficient as the system MUST be linear for all possible inputs and outputs from 0 to their max in order for Bode’s feedback analysis to be applied.

The application of feedback analysis to the climate is completely wrong and in no way can the analysis be subverted to work as it has been applied. Feedback applies equally to all W/m^2 of input, not just the next one. The planet and feedback simply can not tell one W/m^2 from any other. Applying feedback incrementally has absolutely no foundation and defies COE.

Ken Irwin
Reply to  co2isnotevil
December 8, 2021 7:49 am

I think perhaps it might be enlightening to consider the analogous “feedback circuit” the other (and dare I say – proper) way around.
I if I built an electronic amplifier and it produced such chaotic results as a’la “climate” I would presume one of my components was faulty (or a bad joint – whatever).
There is no evidence to suggest that our atmosphere behaves like an electrical amplifier so the application of such formulae and principals are at best wishfully grasping at unrelated physics for some legitimacy and is perhaps only useful as a proximal in the lower range of “feedback” values.

Last edited 1 month ago by Ken Irwin
Reply to  Ken Irwin
December 8, 2021 9:22 am

Yes, my favorite analogy is if an audio amplifier behaved the way the climate feedback model suggests, the output of the amplifier would be unintelligible, much like how the IPCC describes the climate,

Kevin kilty
Reply to  co2isnotevil
December 8, 2021 9:30 am

Your ‘more realistic’ feedback diagram is also incorrect. The issue is that it fails to accommodate the preconditions for applying feedbacik analyss. First is the missing implicit power supply whose purpose is to avoid having to apply COE between the input and output of the network. Second is the requirement for strict linearity. 

The entire power supply for climate is solar irradiance, i.e. insolation, which I have made the input to my revised feedback system. My system is also not linear because it involves the non-linear feedback block (N(A,w)). I don’t understand how you missed this.

Reply to  Kevin kilty
December 8, 2021 12:07 pm

Yes, solar irradiance is the only actual forcing to the system and anything else is a change to the system and must be considered as equivalent to some amount of solar forcing while keeping the system constant. However, the forcing and the power supply can’t be the same thing because the feedback model being applied specifically doesn’t conserve energy between the input and output. When you apply COE to the input and output, then output power can be either feedback or contribute to maintaining the surface temperature, but not both as Bode’s feedback model otherwise allows by assuming output power comes from an implicit, infinite source.

In terms of ordinary amplifiers, the input impedance of Bode’s model is assumed to be infinite while the input impedance of the climate model is the same as the output impedance which is assumed by Bode’s model to be 0.

I didn’t miss your non linear feedback block. It’s non linear and as such doesn’t meet the precondition for applying linear feedback analysis that requires all components to be linear. The only proper measure of feedback is the fraction of output returned to the input which requires the input and output to have the same units. The idea that they can be different arises from Schlesinger’s incorrect conflation of the feedback fraction (Beta) with the feedback factor (Beta * mu), where mu is the open loop gain..

A better model moves the non linearity out of the loop as a transformation circuit converting a linear feedback circuit output expressed in W/m^2 to a temperature using the SB Law. However, the COE problem still exists without an implicit power supply.

Kevin kilty
Reply to  co2isnotevil
December 8, 2021 3:37 pm

Rather than bicker, here, I am just going to refer you to either of my references in [11], or to any other text in control systems.

Reply to  Kevin kilty
December 8, 2021 3:56 pm

There’s a difference between a control system, for example a thermostat controlled furnace and a linear amplifier, although linear amplifiers are often found as part of a control system. The feedback for a heating system is the output of a comparator that compares the output temperature to the desired steady state where the comparator output is 1 or 0, either turning the heater on or turning it off and is definitely non linear feedback,

The model referenced by climate science is Bode’s model of a linear feedback amplifier where positive feedback amplifies the sensitivity. It is not a control system where feedback results in a desired steady state.

Last edited 1 month ago by co2isnotevil
Tim Gorman
Reply to  co2isnotevil
December 9, 2021 5:52 pm

Linear feedback has one of three basic states. Positive feedback, no feedback, or negative feedback. A *linear* feedback system will have one or the other. You can change the between the types but, as you point out, that makes it into a non-linear system.

David Stone CEng
Reply to  Kevin kilty
December 9, 2021 4:17 am

The fact that a feedback block is non-linear does not change the analysis, and your solar isolation is not a simple “x” W/m2, it is the integral of all previous losses and gains as input to the transfer function. This is where the models have difficulty, it is this time-based integral, which makes the result so complex. It could be possible to apply the equation at a point in time, but then the input total energy cannot be different from the output energy at the same instant, thus consideration of the feedback time constants. Clearly, total energy cannot be created, it can only come from the input and any storage that is present in the system. Unfortunately, many computer models think it can!

Tim Gorman
Reply to  Kevin kilty
December 9, 2021 5:59 pm

The power supply cannot be the input also. Otherwise the feedback loop is useless. The input can’t be greater than the power supply so the only way to change the system is to increase or decrease the power supply.

Joseph Zorzin
December 8, 2021 7:47 am

“temperature proxies”

ay, there’s the rub

Ben Vorlich
December 8, 2021 7:55 am

In my mind this is more like how I imagine climate and its feedbacks, except not as simple as this (some variable resistors for example)

comment image

Curious George(@moudryj)
Reply to  Ben Vorlich
December 8, 2021 8:05 am

Simple models have their place. But, as a saying goes, “Interpolate at will. Extrapolate at your own peril”.

Kevin kilty
Reply to  Ben Vorlich
December 8, 2021 9:40 am

One problem with replacing an abstract feedback system with an idealized electronic circuit containing an operational amplifier, is that the operational amplifier 1) has a lot of complicated circuitry within to make it linear, i.e. its output is meant to be proportional to the voltage difference at the inputs, and 2) the power supply to make it all run is nowhere in the circuit. Now this works fine in electronic circuits where we aim to operate near the mid-point of the dual power supply rails, but is nowhere near correct for the climate which obviously runs to the rails every 100,000 years. This is the point I was trying to make with my non-linear diagram.

Peta of Newark
December 8, 2021 8:07 am

Nice that we have someone who appreciates what ‘non-linear’ means – in that a relay is non-linear whereas a wiggly line is linear

You know what I’m gonna say:
1/ The precessions and orbitals are far too small over far too long times scales. Maybe at times they seem to coincide with ‘something’ happening but to mark them as The Cause is Straw Clutching

2/ Yes there is a non-linearity – think of it as the classic sand-in-glass egg timer

The sand is sand after a fashion, except that is everything except sand,
Sand is what’s left after the timer has run its course. The thing that’s pouring through the timer (cliamte system) is and one of the 52 possible Liebig Limiters for plant life

Consider a high-latitude forest. As it lives, it is ever so slowly using up the nutrients it needs from the soil under it.
But at some point, one of its vital nutrients will run out and the forest will die.
This will manifest, because of the change in Albedo as the trees go from green to ‘brown’, as a ‘change of solar insolation
Also, the tress would have, as everyone knows, created their own weather (clouds on a hot sunny day) via transpiration.

But then with the trees dead, dying, diseased and burning (hello hello California) the litter under the trees will continue to oxidise (rot) causing CO2 levels to rise BUT, the trees ain’t there any more to pull it back down again so CO2 will skyrocket
There was/is your temp/solar/CO2 connection. easy wasn’t it?

But also, the litter retained vast amounts of water which would have added inertia (this is the ‘time’ element = lower-case omega in the feedback thingy) because of the vast amounts of heat stored in that water.
It would have cooled the summers and warmed the winters. But with that water gone, the winters would get colder and longer and the, as-stated, ice-albedo effect would come into play and the ice would creep to ever lower latitude.

Scary innit because what is to stop it reaching the Equator and closing the whole thing down.

IOW. Getting into Ice Ages is easy, getting out of them is the pig

But once something does crack the ice (it simply has to be volcanoes pumping out dust and acid rain) and assuming the ice never made to the Equator, the plants will be in heaven.
Because the ice sheets will have ploughed the landscape, removing the tired old soil so lacking in nutrients that it killed the forest, and leaving lots of fresh new, variously pulverised rock, for the new generations of plants to get into.
Plant life would have simply exploded and bulldozed the ice back up to the poles much faster that the ice ever advanced southwards. Thers’s the ‘shape of your interglacial graphs – a classic saw-tooth of rapid advance – slow decline

It breaks all the rules doesn’t it?
Every Last One

Because Ms Whatshername at primary school told you that deserts have no plants in them because they have a crap climate
The lack of plants creates the crap climate..

Simply turn round what Ms Whatshername told you at age 5 or 6 and EVERYTHING fits together
think the unthinkable. be crazy. learn to dance
(and don’t eat sugar)

December 8, 2021 8:17 am

Interesting! So what is the magnitude of the drop in insolation at 65 north needed to trigger a glaciation? Likewise, how much does the insolation at 65 north need to increase to lead the earth out of a glaciation? With CO2, Happer et al show that a doubling of co2 provides a forcing of 3 w/m^2. There really isn’t a lot of forcing directly from CO2 changes to drive climate change unless there are significant feedbacks. How anyone can look at the ice core temperature and CO2 data and say that CO2 is driving the calculated temperature data is beyond me. Is there any other place than the oceans that the changes in CO2 observed in the ice core record could come from? For the oceans to give up CO2, they need to warm. I find it bazaar that one can believe that CO2 just appears and disappear by magic. I’m sure Mark Maslin is a smart guy, but I fail to see how his views on CO2 leading temperature make any sense.

John Tillman
Reply to  Nelson
December 8, 2021 9:07 am

I can’t tell you the precise amount of insolation to start ice sheet melting, nor estimate the tilt angle, as the process also depends upon the other cycles. But during the Eemian Interglacial and its preceding termination, insolation at 65 degrees N varied from over 450 to about 395 W/M^2. That warm spell was hotter than has been the Holocene and so far lasted longer.

Obliquity varies between 22.1° and 24.5° every 41,000 years. Earth’s axis is currently tilted 23.5°. When tilt is less, winters are not as cold and the summers are not as warm. Warmer air can hold more water vapor and therefore, produce more snow during winter months. Because summers are not as warm, the previous winter’s snow does not melt. This promotes glacier formation.

Last edited 1 month ago by John Tillman
Kevin kilty
Reply to  Nelson
December 8, 2021 9:35 am

At their maximum the orbital elements might produce an anomaly for a brief time at 65 N of 40 W/m^2. Huybers’s paper which I reference has an interesting diagram showing the full pattern for essentially one moment in the history of orbital elements and what is interesting about that diagram is that the +40 W/m^2 anomaly is followed within a couple of months at the same location by a -20W/m^2 anomaly. The driving function in my diagram (Is) is surprisingly complex.

Reply to  Nelson
December 8, 2021 11:13 am

No one every comes up with the source of the CO2.

Maybe its warming swamp water emitting CH4 which decomposes into CO2.

Reply to  Lil-Mike
December 9, 2021 11:16 am

It was swamp gas which caused it? Wasn’t that the reason Project Blue Book gave? 🙂

Tim Gorman
December 8, 2021 8:19 am

It’s been 50 years since I used the analog computers in our electronics lab (no PC’s back then) but this would probably be better modeled by them.

Clyde Spencer
Reply to  Tim Gorman
December 8, 2021 12:19 pm

When I worked at Lockheed in the ’60s, we depended on an IBM 360(?) initially, and then later a Univac 1108 machine for most of our computing. Near the main computer room was another large room that rumor had it housed an analog computer. I never saw the lights on in the room or saw anyone working in there.

Are you going to get back to me about my draft paper?

Last edited 1 month ago by Clyde Spencer
John Tillman
Reply to  Clyde Spencer
December 8, 2021 12:39 pm

Wow! You guys are even more antique than I, which I felt scarcely possible.

Clean living or better living through chemistry and medical science?

Clyde Spencer
Reply to  John Tillman
December 8, 2021 8:59 pm

I’m not called a Renaissance Man for nothing! 🙂 Mostly clean living and good genes.

Reply to  Clyde Spencer
December 9, 2021 11:19 am

Lockheed depended on this? Oh wait, that’s Uniblab.

Last edited 1 month ago by beng135
Clyde Spencer
Reply to  beng135
December 9, 2021 11:30 am

I wouldn’t say they depended on it. It looked like it hadn’t been touched in years, although the LMSC buildings were only constructed about 1956 and I started working there about 1962.

December 8, 2021 9:45 am

Was this the entirety of Maslin’s covering letter for publication of this paper –

want to believe.jpg
Kevin kilty
Reply to  Mr.
December 8, 2021 9:54 am

That is a very entertaining poster, but I don’t want to just discount Maslin’s paper as irrelevant — it really was an interesting contribution. However, he did gloss over a real problem. Even if we accept that CO2 plays a large role, CO2 concentration doesn’t just appear or disappear spontaneously — something has to initiate it and that would be a temperature excursion resulting possibly from the orbital elements. I tend to agree with Maslin that CO2 plays an important role especially coming out of an ice age because an 80ppm increase of CO2 when ice volume is large is far more effective as a “greenhouse” influence when CO2 concentration is 180ppm, than it is where we presently are at 400ppm.

Considering this is what made me think of the relay controller in the first place. Table 1 shows a few elements that make up one part or another of the “relay” that connects or disconnects influences that make the cooling stop on the low end, and make warming stop on the other. Undoubtedly there are many other factors in my N(A,w) block.

John Tillman
Reply to  Kevin kilty
December 8, 2021 10:54 am

Also, Earth’s air is drier during glaciations, or more so over more of the planet, than in interglacials, so CO2 has a relatively greater effect.

But it’s at best a bit player, and doesn’t increase until well after deglaciation gets going, which also makes more of Earth’s air wetter.

Kevin kilty
Reply to  John Tillman
December 8, 2021 11:08 am

John, you seemed well informed enough to have perhaps done research in this subject area at one time. I might refer you to the reply I sent to Ron Long earlier. The constant evolution since Pliocene is of growing ice volume, and I read, or think I read, speculation in the literature about the growth of great mountain ranges — Himalayas, Cordillera, etc. having an effect of drying the atmosphere, which of course suggests water vapor is a major influence. Have you heard of this?

We had a “disguished lecture series” speaker come to campus ten years ago or more, who told an amazing tale of the disappearing volatiles. His research suggested that volatiles surface budgets of all sorts, CO2 and chlorine were his principal examples, can’t be closed on the basis of what we know. His conclusion was that there are unrecognized sources of return for these volatiles to maintain a steady state — I wondered at the time if this disappearance of volatiles is genuine and since volatiles also tend to be greenhouse gasses it made for an explanation of the increasingly colder and icy Earth through the teriary. Now no one recalls who this distinguished speaker was, or can even recall the talk. Maybe he wasn’t so distinguished.

John Tillman
Reply to  Kevin kilty
December 8, 2021 11:24 am

It’s not just CO2 whose sinks and sources aren’t well known.

A search for possibly relevant papers on disappearing volatiles turned up nothing.

The rise of the Himalayas has been proposed as one cause of cooling from the mid-Eocene, but IMO the separation of Australia from its Gondwanan neighbors South America and Australia was key.

By the Oligocene, deep channels had opened between the southern continents, isolating and further cooling Antarctica, leading to ice sheet formation and the beginning of the Cenozoic Ice House/Age.

The Indian Plate had previously raced across the Indian Ocean from Antarctica in the late Cretaceous and early Paleogene before colliding with Eurasia, crumpling up the Himalayas.

Ice sheets formed in the Northern Hemisphere after the Isthmus of Panama closed in the late Pliocene.

Kevin kilty
Reply to  John Tillman
December 8, 2021 11:35 am


John Tillman
Reply to  John Tillman
December 8, 2021 11:59 am

Even before the collision, India’s tectonic speed record affected climate, when it passed over the Reunion Island Hotspot, producing the Deccan Traps. Those eruptions did affect climate, but didn’t cause the end Cretaceous extinctions.

The collision raised up the Tibetan Plateau, which has been called Earth’s Third Pole. Increased crust weathering has also bee fingered in climate change by those of the carbonate persuasion.

Last edited 1 month ago by John Tillman
Reply to  John Tillman
December 9, 2021 2:33 am

Some discussions to be had about whether the end of the Cretaceous was a consequence of the Deccan traps or that pesky meteor/meterorite or both.

John Tillman
Reply to  GregK
December 9, 2021 5:28 am

Not really. It’s pretty clear that non-avian dinos would easily have survived the Deccan Traps. The impact, not so much.

Dinos survived the end-Triassic CAMP and thrived, in fact dominated the land thereafter.

Reply to  John Tillman
December 8, 2021 5:10 pm

Didn’t the Orbiting Carbon Observatory settle once and for all the issue of CO2 sinks and sources?

John Tillman
Reply to  guest
December 9, 2021 5:24 am

No. It clarified some sources.

Last edited 1 month ago by John Tillman
Reply to  Kevin kilty
December 8, 2021 5:34 pm

Regardless of the potential logic in his arguments, one still has to deal with all the evidence showing CO2 lagging temperature by a large margin. Things not accounted for, nor perhaps even imagined, are sometimes very important.

John Bell
December 8, 2021 10:15 am

There is 50x the amount of C02 in the oceans as in the air. FIFTY TIMES! If the oceans even burp it makes a big difference in the air. Oceans heat up, more C02 in the air.

Reply to  John Bell
December 8, 2021 12:27 pm

Its the CCD … The Carbonate Compensation Depth. CCD is the depth (read temperature) below which carbonate can’t precipitate. In cold water, carbonate dissolution exceeds precipitation. Hence, cold North American Pacific waters don’t precipitate Calcium Carbonate, we have bare rocks. However in the warmer East Coast, and Gulf of Mexico, we have carbonate sands which have precipitated out of the warm water.

Likewise, when the oceans cool, they have to take up their carbonate, which of course will want to outgas to the atmosphere.

Jim Gorman
December 8, 2021 10:52 am

Kevin, nice article.

it is pleasant to see someone who recognizes that the earth and temperature variations are not based on simple linear regressions between CO2 and temperature.

I have pointed out many times that there are many cycles of varying lengths from the daily rotation of the earth to orbital factors to solstices and equinoxes. They all interact in various and sundry ways with variations in frequency and phase. It would be nice if we could inject a step function and break down the output into frequency variables. But since some are obviously non-linear and phases vary, I’m not sure we can ever develop a fixed system to predict with precision what will happen at any given location at any given time.

Time series analysis is where climate science is missing a lot. No one in the field seems to have any knowledge of how it is done or its importance. Just use simple averages and linear regression. For example, Why is the GAT based on annual temperatures and not on temperatures in the northern and southern hemispheres at a similar season in the earth’s orbit around the sun. Such as NH spring/SH spring or NH summer/SH summer? Doing it based on annual average temps means winter and summer temps are split between years, let alone averages between summer in one hemisphere and winter in the other. TOBS was considered to be worthy of adjusting temps but the big picture was never looked at. This makes no sense to me. At the very least, the hemispheres should be calculated separately and then slid over each other until the seasons coincide properly. Equinoxes and solstices are well known so breaking data into the seasons should be straight forward.

December 8, 2021 11:03 am

Hi Kevin, first off I’d like to say for a better control diagram example, look up what’s called a PID controller.

Wikipedia has a good description, with a good diagram.

comment image

In a PID control circuit, there are three different feedbacks. One course grain, one medium grain, one fine grain. Of course in a control circuit, the goal is to control perhaps the speed of a motor to some desired value. So the feedbacks are the difference between the actual motor speed, and the desired motor speed. Whilst controller circuits and climate models are vastly different things, using the components of the PID controller may help clarify the properties of the different climate components.

Proportionality, the first stage of a PID controller is proportionality, feedback the proportion of the difference between the actual motor speed to the desired motor speed. Feedback the proportion, increased insolation proportionally increases temperature.

Integral, the second stage of the PID controller is the integral of the difference. This is the medium tune knob. Feedback the integral of the difference. The integral feeds back cumulative change. Such as cumulative CO2 causes cumulative forcing.

Derivative, the third stage of the PID controller is the derivative of the difference. Feedback the derivative of the slope of change. This feeds back things that will change in the future. Such as the derivative of increasing CO2 is increasing biomass, which thus is a negative feedback to CO2.

But as I think more about this, the more I realize there are many components to the climate. A better model is to treat each component with a PID controller of it’s own. Especially that there are feedbacks from each component to the other components, i.e. complex wiring. Thus, what is needed in climate science is not a formula of the climate, but a simulation model. Especially that some components will respond to feedback or inputs not immediately, but delayed. Likewise, some components will have multiple effects, such as clouds reducing insolation, but also providing insulation.

What I’m considering missing from the climate is the botanical feedback. Yes, we’re melting the permafrost, but also gaining swampland. What are the different feedback properties of swamp v.s. tundra? Granted, not all permafrost is tundra, some is forested permafrost, how do those differ in insolation, CO2 production/consumption, hydrocarbon aerosols?

Ocean heat oscillation/transport, of course this causes different effects in different continents, such as ENSO causing one thing in North America, and another thing in Australia. Also AMO, and I suppose there is an Indian Ocean component too.

But most of all, I think you need to break this whole thing down to a place. The idea of modeling or simulating the whole earth can’t happen in one stage. Each medium/small scale climate needs to be modeled independently. Cloud cover in San Francisco produces quite different effects than cloud cover in Death Valley. Daytime/nighttime clouds produce much different feedbacks in these different climates. Somewhere we need to differentiate cloud types and their effects/feedbacks. But if we view each component with it’s own PID controller, we will start to see a clearer picture.

Last edited 1 month ago by Lil-Mike
To bed B
December 8, 2021 11:23 am

I’m not sure that any feedback loop is valid. A significant area of land above 65° N was not covered in glaciers.

Norilisk in Siberia is 69°N and gets a daily average of over 14°C in July (average maximum of 18). For it to be freezing in July because of lower insolation requires a drop of 18%.

A bit of dust is not much of a change in albedo compared to a puddle of water.

The ice sheets are in areas of little precipitation, mostly snow. 1000 mm of rain per summer would be a comparable amount of heat to the insolation. A lot less would lead to lakes and a massive drop in albedo.

Any feedback would be related to weather patterns rather than global temperature.

Clyde Spencer
Reply to  To bed B
December 8, 2021 12:29 pm

A bit of dust is not much of a change in albedo compared to a puddle of water.

However, dust in or on snow is less sensitive to the angle of incidence of sunlight than a puddle of water.

To bed B
Reply to  Clyde Spencer
December 9, 2021 10:38 am

Just pointing out that it’s silly to try to explain this with a feedback dependent on anything global unless you actually know how weather patterns respond to it.

Reply to  To bed B
December 8, 2021 12:35 pm

Norilisk in Siberia is 69°N and gets a daily average of over 14°C in July (average maximum of 18). For it to be freezing in July because of lower insolation requires a drop of 18%.”

I would think this is due to the permafrost creating a heat depression (opposite of a heat island.) Proximity to a large block of ice which is pulling away radiant heat.

Steve Z
Reply to  To bed B
December 9, 2021 3:05 pm

It is generally accepted by geologists that North America was covered by glaciers up to a kilometer deep, as far south as Missouri, a few tens of thousands of years ago. Most of this area is ice-free in summer now.

The water to form this ice had to come from a large body of water nearby, either the north Pacific, North Atlantic, or possibly the Arctic or Hudson Bay. The land areas near the Arctic Ocean and Hudson Bay have low precipitation in winter now (due to their freezing in winter, and some of the summer precipitation is rain), and Pacific moisture is mostly prevented from reaching the central plains of Canada by the Cascade Mountains.

But if there was a time during which the Arctic was ice-free year-round (possibly during a time of minimum tilt of the earth’s axis, this could have created an increase in snowfall on the nearby land, and started a glaciation. The increase in albedo could have reflected away more sunlight, then a decrease in insolation could have speeded up the buildup of the glaciers, until the Arctic re-froze and “starved the glaciers for moisture”.

December 8, 2021 11:31 am

Yes, it would be good news unless you’re a climate change zealot.

Clyde Spencer
December 8, 2021 11:46 am

Insolation anomalies at 65 north which fail to start the escape from an ice age are in a few cases larger than insolation values that initiate an escape.

Might it be that these apparent variations are the result of measurement errors?

Kevin kilty
Reply to  Clyde Spencer
December 9, 2021 2:36 pm

A bit worse than measurement error — they are calculated from orbital elements, although to be fair we can calculate these elements quite accurately for a million years in the past.

Keith Rowe
December 8, 2021 11:50 am

Oceans. The greatest effect to today’s climate and every timescale. My take is with the current configuration of the continents when the deep ice age is happening, there is a stratification of heat in the oceans, a build-up of energy. There is only one way for the world to build up enough energy to melt the giant glaciers and change the dynamic of ice sheets reflective surface. Ocean currents change might be triggered by Milankovitch cycles that start the cycle of turning on the ocean conveyor pushing cold waters to the bottom of the ocean and pushing up the warm build up of waters to the poles that start melting and the cycle continues. As the ocean gets colder and the mixed layer gets thinner and thinner as the planet goes through warm and cooling cycles as the warm waters get wrung out and there isn’t enough energy to sustain and the world goes into cold deep ice age. This is noted in changes in oceans at the inflection so ocean currents at the beginning and end of the interglacials. Explains DO events when there isn’t enough energy built up to sustain. The amount of energy required to keep the warming going. Today’s warming as a part of the Atlantification of the Arctic ocean. We are going to go back into a deep ice age. Enjoy the warm weather.

December 8, 2021 12:05 pm

Maslin used to be a good geoscientist but now he’s gone alarmist Taleban and as such, is no longer a source of objective science.

Mickey Reno
December 8, 2021 12:08 pm

If Dr. Maslin had meant WATER VAPOR when he says ‘greenhouse gasses’ he’d be closer to being correct. But even then, he’d still most likely be wrong, because it’s not the IR interception of water vapor that’s most important, but the amount of water being pushed around the atmosphere by convection and winds. We know he does not mean water vapor in either sense.

If the approximately 800 year lag in CO2 increases is real (and our best scientific understanding of the ice cores says it is real), then Dr. Maslin must successfully explain a hypothesis as to why the ends of Inter-Stadials (the warm parts between glaciations) occur when CO2 is at its maximum. If the hypothesis is that CO2 CAUSED the warming, then the ends of those Inter-stadials would not have happened. THEY DID HAPPEN. THE HYPOTHESIS is FALSIFIED. I feel this point is completely dispositive, and shows that CO2 is a bit player in glaciation/de-glaciation cycles.

I agree with the Author, Kevin Kilty when he says the feedback models are far too simplistic, but I say they miss thee boat completely, in that they try to pin these big changes on atmospheric chemistry in the first place. No such fact is in evidence. Glaciations caused by orbital mechanics change the lengths and nature of summer and winter in the N. Hemisphere. Summers become shorter and cooler, winters become longer and warmer. The only chemistry that matters is, how much heavy wet cloud is being pushed onto the land area during the longer, warmer winter seasons, how much precipitates out as snow, and how much (OR HOW LITTLE) snow melt is occurring during the shorter, cooler summers. Convection, cloud, precipitation as snow cause the beginnings of all the glaciation periods, and those climate features appear to be oblivious to minor differences in CO2. concentrations (between 180-300 ppm). Feedback loops certainly exist, no doubt. Less sunlight penetrates the heavy wet cloud layer. Maybe this helps solidify ice during clear winter days and nights. Albedo goes up when sunshine hits white snow and ice. But the feedbacks must be incidental, too. The ice eventually melts in spite of the feedback, because the orbital mechanics slowly warms and lengthens NH summers and shortens and cools NH winters, making for less precipitation as snow.

December 8, 2021 12:18 pm

In alarmist groupthink, a single tortuous, fudged, bizzaro-logic, model-mangled pal-published “finding” is brandished as the final word on a topic, and an entire scientific discipline and literature that hitherto contradicted the “finding”, simply cease to exist.

Grotesque stunts like Maslin’s only make it clearer – if such were needed – the foundation of pure dishonesty on which climate alarmism slips and slides, bobs and weaves.

December 8, 2021 12:45 pm

Abstract of Willie Soon’s review of the subject in 2007:

A review of the recent refereed literature fails to confirm quantitatively that carbon dioxide (CO2) radiative forcing was the prime mover in the changes in temperature, ice-sheet volume, and related climatic variables in the glacial and interglacial episodes of the past 650,000 years, even under the “fast-response” framework where the convenient if artificial distinction between forcing and feedback is assumed. Atmospheric CO2 variations generally follow changes in temperature and other climatic variables rather than preceding them. Likewise, there is no confirmation of the often-posited significant supporting role of methane (CH4) forcing, which—despite its faster atmospheric response time—is simply too small, amounting to less than 0.2 W/m2 from a change of 400 ppb. We cannot quantitatively validate the numerous qualitative suggestions that the CO2 and CH4forcings that occurred in response to Milankovic orbital cycles accounted for more than half of the amplitude of the changes in the glacial/interglacial cycles of global temperature, sea level, and ice volume. Consequently, we infer that natural climatic variability—notably the persistence of insolation forcing at key seasons and geographical locations, taken with closely related thermal, hydrological, and cryospheric changes (such as the water vapor, cloud, and ice albedo feedbacks)— suffices in se to explain the proxy-derived, global and regional climatic and environmental phase-transitions in the paleoclimate. If so, it may be appropriate to place anthropogenic greenhouse gas emissions in context by separating their medium-term climatic impacts from those of a host of natural forcings and feedbacks that may, as in paleoclimatological times, prove equally significant.

December 8, 2021 12:46 pm

If you don’t want glaciation in the northern hemisphere, reopen the isthmus of Panama.

Reply to  Agamemnon
December 8, 2021 4:49 pm

There will still be glaciation but it will only occur with each precession cycle.

December 8, 2021 12:49 pm

Excellent at first read, Kevin. A lot of useful thought, will have to re-read carefully.

Glad to see a criticism of the use of the op-amp cartoon too frequently used by critics of AGW. As a retired EE I shudder whenever I see it used by writers unfamiliar with the real thing… even by my Lord Christopher Monckton of Brenchley, apparently endorsed by the irrepressible Willie Soon.

It is sheer nonsense, although at first glance it appears to be an reasonable analogue representation of the (always simplistic) feedback relationships (in climatology), as
y = x G/(1+Gf) where x is the system input, y the system output, f the feedback fraction and G the system gain. There are several things wrong with this representation as applied:

(1) Where is the power source for the amplifier?
The engineering assumption is that the power source is essentially of zero impedance and quasi-infinite, so that any drain by the amplifier can be neglected. What is being controlled is potential, not power. 
In climatology the only power source is Old Sol. While only small variations of the order of 0.3% are observed, this source is limited at the TOA to a total average value ~ 1350 w/sq m, 24/7, but varying locally from zero (night) to a higher value within the tropics at noon.
And what is being controlled? Well, the ground effect of Old Sol on temperature by some system parameters embodied in the amplifier diagram. Sounds a bit like an Escher engraving, doesn’t it? Hoist by its own petard.   

(2) The amplifier is shown as having a gain G. What process, in nature, ever has a gain more than unity? Name one. Don’t give me catalysis or enzyme activity – these are physical processes that overcome a potential barrier that allows an unstable equilibrium to exist.
Think California, 21% oxygen in the atmosphere and a lot of summer dried dead vegetation co-existing on the ground. Catalysis – a spark from an auto, a careless camper or smoker, a lightning strike and you have its annual forest fires – oh, I forgot, add poor forestry and, of course, the political stupidity that abounds there.

Explosive nuclear fission & fusion? Same arguments.
I don’t advise trying it, but fill a flask (indoors & carefully!) with equal volumes of H2 & Cl2 gas. Nothing happens – if you keep it in a dark closet. Take it out in sunlight and bang! a chain reaction initiated by photons causes extremely rapid chemical fusion to HCl. A barrier has to be overcome to release the latent energy.

The argument contra G>1 can be logically overcome by forcing G==1 or very close by showing the fuller op-amp cartoon as having both + and – inputs (and please add the positive and negative supply lines required as vertical lines. per (1) above). Just strap output directly to the negative input. You can then use a summing device on the plus input for the feedback.

(3) No process is instantaneous. G has a time delay, the feedback network has a time delay. No amplifier is perfectly linear, and few feedback networks are either. Many processes are inherently non-linear. An example of delay is the ~ 7 week delay between solstices and maximum temperature; of nonlinearity, the exponential absorption of radiation through a medium. &c.

(4) If you need any significant power to drive the load – what use is a controller otherwise? The idealized op-amp has zero output impedance and hence infinite potential power output but if you believe any real device has these properties, I have a bridge to nowhere for sale… Whatever this load is (it is rarely shown) you need to add a power amplifier – and what is the power source for this? – Old Sol again.

There is more but enough said! Thanks, Mr. Kilty, for airing this on WUWT.

Reply to  R.T.Dee
December 8, 2021 7:47 pm

Error, mea culpa! Equinoxes not solstices.

December 8, 2021 12:55 pm

Our 34-million-year Ice Age started with glaciation of Antarctica, and in last couple million years, we got the “permanent” glacial icesheet of Greenland and arrived at coldest time period of the 34 million year Ice Age, which is called, Late Cenozoic Ice Age though also called,  Antarctic Glaciation:Late Cenozoic Ice Age – Wikipedia

It’s commonly accepted that our global will not warm Antarctic and melting of Greenland is
more likely. Whatever reasons given, it makes sense as the Greenland was the last frozen in the 34 million years of global icehouse climate. So, expecting Greenland to first thaw, seems reasonable. The idea the Greenland could melt is delirium, but if our frozen world were to get a lot warmer {which it hasn’t} Greenland is likely to melt first.

But Holocene has pasted its peak warm period over 5000 years ago, and peak Holocene was when Earth had ice free polar sea ice in the Arctic with presently frozen tree stumps being living trees. And most Sahara Desert was grassland {with forests and rivers and lakes] which dry wasteland presently.
This warm period called, Holocene Climate Optimum:
Holocene climatic optimum – Wikipedia
In my opinion, was warmer because Earth’s ocean was a lot warmer.
But the question I would give is, if Sahara was Green like it was green for thousands of
years, and thousands of years ago, would Earth with green Sahara be a warmer Earth.
And if were we to have ice free polar sea ice in arctic and the biggest forest in world {this northern forest] was growing a lot more. Would that be a warmer world?
Or a similar question, would that mean, that Earth’s global water vapor, had to increase significantly from our current global water vapor.
And of course CO2 levels were much lower back then. And the main thing CO2 is suppose to do is increase global water vapor {because CO2 is a weak greenhouse gas compared to water vapor, but higher CO2 are suppose to “force” higher water vapor].
Though having our cold ocean get warmer, would seem to force higher global water vapor, yes?

Reply to  gbaikie
December 8, 2021 1:13 pm

Btw, our cold ocean which averages about 3.5 C, was colder in the Little Ice Age which is said to have ended at around 1850 AD.
If the ocean becomes colder, does that reduce the global water vapor?

{the correct answer is, yes}

Reply to  gbaikie
December 8, 2021 1:19 pm

If you dump a trillion cubic meter within one year on to the Sahara Desert, does that
increase global water vapor.
US uses .6 trillion cubic meter of water per year. China and India each use about 1 trillion cubic meter of water per year.
A trillion ton of water is not a lot of water, in terms of Earth the water planet, which dumps a billion ton of rain in any rainy day.

Reply to  gbaikie
December 8, 2021 3:41 pm

The turnover of atmospheric water each year is estimated at 522,000Gt. The actual mass of water in the atmosphere varies a little but is typically 11,000Gt. Thus, on average, the atmospheric water has a residence time of a week.

Atmospheric water is at its minimum when the ocean radiated energy uptake is at its maximum and the land radiated energy loss is also at its maximum. The energy goes into evaporating water that gets rapidly transferred to land where it precipitates to effectively warm the land. The global land mass always has a radiated energy deficiency and the oceans always a net gain. The Earth would be warmer if it was all water covered.

The idea of CO2 causing a positive feedback loop with atmospheric water is laughably naive.

The ocean surface is coolest when ocean energy uptake is a maximum. The water cycle, ocean to land, reaches its maximum in December or January and that is when the oceans are coldest. Oceans are warming because the water cycle (ocean to land and return) is slowing down:
The consequence of insolation over oceans declining as the precession cycle progresses.

December 8, 2021 1:39 pm

I can reproduce sea level changes for the last 400k years using orbital mechanics, upper and lower limit conditions and an ice albedo change once the lower limit is reached:!Aq1iAj8Yo7jNhEUPzdLmLlSCh3_I

This correlates well with the nuances observed in reproduced sea level changes. The precession cycle is clearly visible but eccentricity dominates the cycle now.

Since the Panama isthmus emerged, glaciation occurs over multiple precession cycles but going back 2Mya, glaciation followed the precession cycle.

The longer glaciation cycles now observed are linked to both eccentricity and precession. Glaciation requires the eccentricity to be reducing. Recovery from glaciation requires eccentricity to be increasing.

I could not get recovery from glaciation without changing the ice albedo. There is solid evidence for dust build up at the depths of glaciation. Much of the CO2 available before glaciation gets sequestered under the ice. The low CO2 levels reduce vegetation.

Earth is currently into the next cycle of glaciation – reducing eccentricity and perihelion moving toward the boreal summer solstice or, more importantly, aphelion occurring during the northern winter resulting in increased boreal winter snowfall.

Not many people know that the peak daily insolation occurs at the South Pole at the present time; just under 600W/sq.m averaged over the day. However the net uptake of that insolation is close to zero due to the ice reflectivity. Once snow starts to fall in large volumes, it takes a lot of sunlight to get it to melt. So it is the deposition of the snow that is important. That will increase in northern latitudes as the current precession cycle advances over the next 10,000 years.

Kevin kilty
Reply to  RickWill
December 9, 2021 2:40 pm

I downloaded a copy to have a careful reading. Looks interesting.

Joe Born(@jhborn)
December 8, 2021 3:28 pm

This comment doesn’t really go to the point of your post, but for what it’s worth I’ll mention that Fig. 2 of my “electronic analog” piece provides another example of nonlinear feedback. 

In that case, though, there was no frequency dependence, because the Christopher Monckton theory debunked in my post deals only with equilibrium behavior.

Kevin kilty
Reply to  Joe Born
December 9, 2021 1:49 pm

That was a good essay, Joe, Anthony’s caveat notwithstanding, and the voltage controlled current source in the feedback circuit is just the sort of non-linear element required for a “soft relay”. I like using a relay because people can identify with on/off control if they are familiar at all with their heating system.

There are long periods in which I am absent from WUWT because I get busy on something else, and I often miss good essays during these periods.
Thanks for pointing this out.

Gary Pearse
December 8, 2021 11:05 pm

I cant understand why chemists and chemical engineers haven’t been all over the climate models with big boots on. The Le Châtelier Principle in Chemistry states that in a system of multiple interacting components – chemical compounds, pressures, temperatures etc., any attempted changes to the system is resisted by the system such that the final equilibrium is only modestly changed.

The system accomplishes this by each of its components making small changes, such as precipitating some dissolved compounds, dissolving others causing endothermic or exothermic reactions to procede, expanding or compressing gasses. This principle is wellknown to chemical production engineers who manipulate a system to increase production and quality of products at lower cost so it’s not pie in the sky stuff. It is used to predict the directions chemical reactions will take under different physico-chemical conditions.

Also, you can be assured that it acts in the climate system as advertised, unlike electronic feedback analogies because the climate system is such a chemical system! It includes the biosphere’s interactions with the atmosphere and the soil and seawater, enthalpy changes, cloud formations, photosynthesis of plants (their growth is an endothermic reaction BTW, so sequestering increasing C02 is a cooling event!), driving meteorology and ocean currents.

Intuition suggests that the more components in a system, the greater the resistance to change is marshalled by the system. The climate is a huge multi component ‘tuned’ one.

How to apply it? Let us grant that the 300% overestimate of warming that was made over 30yrs ago was an honest effort and no fault could be found with the physics. This would mean that they should have multiplied their equation by a Le Châtelier coefficient of of 0.33!

Finally, I have to ask. Do physicists know of this principle? Climate modelers definitely don’t.

Jim Gorman
Reply to  Gary Pearse
December 9, 2021 6:12 am

Great comment.

Clyde Spencer
Reply to  Jim Gorman
December 9, 2021 11:43 am

I agree!

Kevin kilty
Reply to  Gary Pearse
December 9, 2021 1:54 pm

Yes. Physicists and engineers, not all of course, but some do know this principal. It seems to be related to a principal that Prigogine annuciated — that linear constitutive which hold best near equilibrium led to minimum entropy generation rate. In contrast the climate research community often think that entropy generation rate is maximized. This comes I think from Lorenz, who seemed to think that energy must be dissipated at fastest possible rate.

Kevin kilty
Reply to  Kevin kilty
December 9, 2021 2:43 pm

 linear constitutive which hold best near equilibrium led to minimum entropy generation rate

correction: linear constitutive laws which hold best near equilibrium lead to minimum entropy generation rate

December 9, 2021 6:44 am

Meanwhile the cooling climate results in declining levels of CO2 and water vapor in the global atmosphere which cools the climate further in a positive feedback loop.”

The sentence above refutes the concept that CO₂ levels precede temperature changes.
The same happens in reverse when climate warms resulting in increasing CO₂ in response to that warming.

Nor are models trustworthy.
Models are hardcoded programs written by people following their own and their program designer’s System design.

As discussed many times here, models, that is, programs have limitations, inconsistencies and gaps that prevent them from demonstrating any thing but imitations of climate, not accurate representations.

December 9, 2021 1:26 pm

What part of “weakly periodically forced nonlinear oscillations in a dissipative bistable excitable medium” does Maslin not understand??

Just can’t get the staff.

Ian MacCulloch
December 9, 2021 8:49 pm

Interesting. Blue ice dating back to 3.2 million ice has been mapped and dated at high altitudes in Antarctica. Vostok 3 had it reached basement would have a date at the at the interface of about 1 million years. Using the recently released information (A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century ( on Camp Century ice corehole in Greenland that did go to basement along with GISP 2 point to a temperate climate. about 1 million years ago and preceding that time. From the moment on both Greenland show constant ice accumulation unaffected by the many ice ages during that period. The constant ice accumulation is at odds, as represented by these deep core holes at either ends of the earth’s surface, with the behaviour of the ice sheets over the same period.
It would seem that there is no clear cut explanation for this contradictory behaviour.

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