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Predictable and unpredictable behaviour

Filed under: — rasmus @ 13 March 2017

Terms such as “gas skeptics” and “climate skeptics” aren’t really very descriptive, but they refer to sentiments that have something in common: unpredictable behaviour.

Statistics is remarkably predictable
The individual gas molecules are highly unpredictable, but the bulk properties of the gases are nevertheless very predictable thanks to physics. More specifically the laws of thermodynamics and the ideal gas law.

The bulk aspects of the gases are a result of the statistical properties of a vast number of particles. Statistics is surprisingly predictable even if the individual cases are not.

Just look at Las Vegas and the insurance industry which make a living on the fact that probabilities (statistics) are predictable. Even economists pin their hope on statistics, and the medical sciences would never be where they are now without the predictive power of statistics.

A “gas skeptic” would say that you cannot predict the state of the gas because the molecules are unpredictable. This is analogous to saying that climatic states cannot be predicted because the weather is unpredictable (a “climate skeptic”).

Climate is weather statistics
Climate can be viewed as weather statistics. Early climatological work was dedicated to survey of how the weather statistics varied from place to place and over the seasons.

There are clear effects of physical factors (latitude, mountains, distance to the coast) on the statistical character of the weather and the weather statistics (climate).

In other words, the statistical properties are a result of the physical processes and conditions present and are readily predicted from e.g. geographical factors, seasonal variations in the solar inclination, the atmospheric composition and the planet’s distance to the Sun.

The weather statistics (eg probabilities) are predictable in spite of the chaotic and nonlinear character of weather itself.

Common misconceptions
There are some examples where the question about predicting the exact state is mixed up with the question of predicting the statistical properties of the system, even by people with some experience in climate research.

Some of them are useful for further learning, and there is a number of them in a ‘report’ (“Climate models for the layman”) that Judith Curry has written for a British interest group that calls itself “GWPF”.

Curry’s report has also been used to back Norwegian contrarians who support the effort of a populist politician to get a seat in the parliament.

The analogy to a “gas skeptic” above illustrates why Curry’s claim is misconceived because it is false that the climate models are unfit to make predictions about the future climate just because the atmosphere behaves in a nonlinear fashion due to the Navier-Stokes equations.

The Navier-Stokes equations describe the atmospheric flow (winds), but the key equations for climate change involve the laws of thermodynamics and the way the different gases absorb different frequencies in the electromagnetic spectrum.

The most important nonlinear component in this respect include scattering processes, phase transitions, and cloud formation.

A potential feedback paradox
Curry also introduces a potential paradox in her report when she emphasises natural variations. The magnitude of natural temperature variation are regulated by feedback processes and have physical causes. The climate sensitivity also involve such feedback processes.

Any feedback process based on temperature will act on both natural and forced changes in the temperature. If such feedbacks result in pronounced natural temperature variations, they also imply that the climate sensitivity is high.

Examples of such feedbacks include increased atmospheric humidity and reduced snow/ice cover. Processes involving clouds are more uncertain, but they too are likely to be affected by temperature (convection) and act to modify the climatic response.

Natural variations may arise from both variations in the climatic state (eg ENSO, NAO, and PDO) or from external causes, such as changes in the sun and volcanic eruptions.

There are also feedbacks relevant to forced variation as well as internal variability which don’t always mean that higher amplitude natural variability necessarily indicates greater climate sensitivity.

For example, the fact that there is enhanced variability in the 3-7 year ENSO band is a result of climate dynamics (Bjerkenes feedbacks) resonating with wave propagation timescales.

Other examples include distinct oscillatory models of variability with decadal and longer timescales, related also to oceanic Rossby wave propagation and gyre spinup processes, or timescales associated with the AMOC.

It is possible to get enhanced variability on those timescales as a result of dynamical mechanisms without needing to appeal to higher climate sensitivity.

Nevertheless, the bottom line is that Curry must prove that the feedbacks involved in the natural variations are different to those affecting the climate sensitivity before she can conclude that natural variability dominates over a warming due to increasing greenhouse gases.

It’s not the sun
When Curry believes that the changes in earth’s temperature are due changes in the sun, it is important to keep in mind that the variations in the sun only affect as a small fraction of earth’s energy input. Amplifying feedback processes are needed to explain the magnitude of the observed changes.

Curry makes a point of the temperature increase before the 1940s, and that the CO2 concentrations were low then. But she seems to have forgotten that the forcing is proportional to the logarithm of the concentration: the effect of an increase is initially higher with lower concentrations.

The changes in the climate before 1940 were a result a combination of factors when there was an increase in the number of sunspots that coincided with increasing CO2-concentrations.

It is well-known that the sunspot record suggests an increase up to the 1950, but various solar indicators indicate no long-term trend in the sun since the 1950.

Only the increase in the greenhouse gases can explain a forced warming since the 1950s because no other physical forcings exhibit long-term trends since then.

Problematic statistics
Another issue is that early temperature record does not give as complete global data coverage as more recent measurements. The global temperature analysis is based on smaller sample in the early part, for which we expect to see stronger random sampling fluctuations.

This is consistent with what Figure 4 in Curry’s report shows. However, she misinterpreted this as being strong natural variability in the early part of the record.

Curry also makes the same mistake as John Christy by using the ensemble mean as a yardstick for the models (here): model evaluations must be based on the individual simulations taking into account the spread of the ensemble run.

It’s not just the temperature
The climate sensitivity is one indicator for the consequences of a global warming which only accounts for the change in temperature, but it is important not to ignore that changes in the global hydrological cycle may also have a severe impact on society.

It is possible that a weaker temperature increase is associated with a larger shift in the convective activity and more pronounced changes in the rainfall patterns (Benestad, 2016).

The comprehensive picture and consistency
I often find it useful to look at the comprehensive picture in science and look for consistencies, both when it comes to physics and the logic.

A curious twist in Curry’s report is (a) her claim that climate models have exaggerated climate sensitivity because they did not reproduce the observed warming over the 2000-2015 period and then (b) her emphasis on natural variations having scales of “weeks, years, decades, centuries and millennia”.

If the claims hypothetically were correct, then how would she know that the temperature variations over brief intervals are not just a result of the natural variations that she emphasised?

We should expect some brief periods with both rapid as well as slow warming (Easterling and Wehner, 2009), and some of the model simulations have indicated a weak warming over the same period. This is explained in the IPCC AR5 (Box 9.2).

Another question is whether the warming rate reported by the AR5 was correct, and more recent studies suggest artificially weak warming connected to changing observational networks (Karl et al, 2015). This has been discussed here. Hence, Curry’s claim about slower warming rates has lost substance.

There is a curious remark in Curry’s report about the climate models’ inability to match the phase and timing of the natural variations. Yes, it is true, but it is also a well-known fact.

The way it is stated in the report makes me think that Curry has not understood what the climate modelling community is trying to do, however. My suspicion is strengthened when she makes a point about the model simulations not including future changes in the sun and volcanic eruptions.

The elementary misconceptions revealed by Curry’s “Climate Models for the layman” surprise me. Does she really not understand the flaws presented here or is she trying to sow confusion?


  1. R.E. Benestad, "A mental picture of the greenhouse effect", Theoretical and Applied Climatology, 2016.
  2. D.R. Easterling, and M.F. Wehner, "Is the climate warming or cooling?", Geophysical Research Letters, vol. 36, 2009.
  3. T.R. Karl, A. Arguez, B. Huang, J.H. Lawrimore, J.R. McMahon, M.J. Menne, T.C. Peterson, R.S. Vose, and H. Zhang, "Possible artifacts of data biases in the recent global surface warming hiatus", Science, vol. 348, pp. 1469-1472, 2015.

218 Responses to “Predictable and unpredictable behaviour”

  1. 201
    Mike Flynn says:

    Mal Adapted,

    Neither you, nor anyone else, has ever managed to make a thermometer hotter by raising the concentration of CO2 between the thermometer and a heat source,

    Tyndall’s experiments showed precisely the opposite. That is, reducing the amount of CO2 or other supposed GHG between a thermometer and a heat source, causes the temperature to rise.

    None of the others you mentioned performed experiments demonstrating the existence of the GHE.

    Climate is defined as the average of weather which has already occurred. Nobody can even define what the climate of California is, let alone the climate of the world.


  2. 202
    MA Rodger says:

    Mike Flynn @194,
    Rather than see your unconstrained trolling in this comment thread, can we see what happens when we try a sensible approach to your commenting?

    You ask us “Do you think I am being unreasonable in wishing to see some experimental support for the supposed GHE?” From past experience, the answer is probably “Yes. It is evident that you are ‘being unreasonable’.”
    But let us ignore the past and turn a new leaf.

    You continue ” Nobody can even say why the effect doesn’t seem to work in the dark, indoors, when it’s very cold, or very hot (as in the hottest places on Earth – characterised by a lack of the supposed GHG H2O), or inside a CO2 cylinder, and so on.” (My bold)
    Is what you say correct? Taking the first part of this statement first, why do you say the greenhouse effect “doesn’t seem to work in the dark”?

  3. 203

    Mike, you haven’t answered my question. Why is the Earth’s surface not frozen over?

    Do you understand why I’m asking this?

  4. 204
    Hank Roberts says:

    ignoramus ignorabimus

  5. 205
    Ray Ladbury says:

    MF: “Neither you, nor anyone else, has ever managed to make a thermometer hotter by raising the concentration of CO2 between the thermometer and a heat source.”

    Mike, you need to consider the flow of energy, not just the ultimate source of the energy. Energy flows from the Sun to Earth. Most of that energy is in the form of visible light. CO2 doesn’t affect that flow, as it doesn’t absorb in the visible. With me?

    The sunlight warms Earth. Earth radiates in the IR with a spectrum characteristic of its temperature. It is LOSING energy. In vacuum,it would radiate roughly as much energy as it takes in from the Sun and maintain an equilibrium temperature. If energy in decreased, Earth’s temperature would decrease, and energy out would decrease in compensation. And vice versa. Still with me.

    Now, let’s surround Earth with a magic gas that lets in visible and absorbs IR. Energy from the Sun still gets in, but IR energy radiated by Earth is blocked. It cannot escape from Earth to the inky blackness of space. What will happen to Earth?

  6. 206
    Mal Adapted says:


    None of the others you mentioned performed experiments demonstrating the existence of the GHE.

    Perhaps (again, pigs might fly) our co-opted culture warrior MF is able to tell us, in his own words, just what all the 19th-century scientists I cited in my previous comment did contribute to the world’s understanding of climate. I’m curious to see what he’ll come up with.

    Failing that, we may assume he is informed solely by his cultural identity.

  7. 207
    Mack says:

    @203 BPLevenson
    “Mike, you haven’t answered my question. Why is the Earth’s surface not frozen over?
    Do you understand why I’m asking this?”
    I will answer your question on Mike’s behalf.
    I understand why you are “asking this”….it is because you believe that there’s a “greenhouse” effect in the atmosphere which prevents the oceans becoming completely frozen solid. The atmosphere “surrounds the Earth like a blanket and stops it from totally freezing up.”
    This is what was drummed into you at primary school and reinforced with actual calculations and numbers in 1st year University physics class.
    On a previous comment to me you indicated that the earth was too far away from the sun…ie there’s not sufficient solar radiation to keep us at our liveable temperatures.
    Well, you would be lead to believe this if you subscribe to the IPCC Earth Energy Budget diagrams which show only about 168w/sq.m of solar radiation arriving at the surface of the Earth….certainly insufficient solar radiation…only enough, so the calculations say, to bring the global average up to about -18deg C…= oceans frozen solid.
    The thing that bothers me, BPL…is that the last time I looked at the wasn’t frozen solid…but don’t worry, I’m assured by you and all the scientific experts that the ATMOSPHERE is preventing this from happening. Forgive me for making a stupid suggestion…but could it be the SUN that melts all the ice ??

  8. 208
    Mack says:

    @203 BPL
    The Earth’s surface is not frozen over because it’s the sun, stupid.

  9. 209

    “Tyndall’s experiments showed precisely the opposite. That is, reducing the amount of CO2 or other supposed GHG between a thermometer and a heat source, causes the temperature to rise.”

    Mike, glad to see that you have taken note of Tyndall’s experiment, as I mentioned.

    However, you appear to have neglected what I said next. Why was the experiment evidence for the greenhouse effect? It was, and remains so.

    If you figure that reason out, you will have done more than just provide amusement for RC readers–you will have actually learned something.

    I already gave you a hint, with my remarks about transparency in the visible wavelengths, etc.

  10. 210

    Mack 207: Forgive me for making a stupid suggestion…but could it be the SUN that melts all the ice ??

    BPL: No, it couldn’t, Mack, and that’s what the math is all about.

    Forget what gets through to the surface. Let’s find ALL the solar energy falling on Earth and see if it’s enough.

    The Solar constant is about 1362 watts per square meter. But because Earth is a sphere, its surface area is 4 π R^2, while its cross-sectional area–which intercepts the sunlight–is only π R^2. So Earth only gets 340.5 watts per square meter of surface area.

    But not all that gets absorbed. Some gets reflected away–about 30%. The climate system absorbs 70%, which is 238 watts per square meter.

    Now, take the “Stefan-Boltzmann law,” which relates flux density (watts per square meter) to temperature (kelvins, which are the same as degrees Celsius). The flux density follows the fourth power of temperature–something twice as hot radiates sixteen times as much energy!

    Invert it to find the temperature from the flux density:

    T = (F / σ) ^ 1/4

    The Stefan-Boltzmann constant, σ is 5.670367 x 10^-8 watts per square meter per kelvin. The temperature sunlight can bring the Earth to is therefore 255 K.

    Water freezes at 273 K.

    So if all the sunlight absorbed by Earth’s climate system were concentrated at the surface, it STILL would not be enough to melt Earth’s oceans.

    Do you see the problem?

  11. 211

    Mack 208: The Earth’s surface is not frozen over because it’s the sun, stupid.

    BPL: No, that’s not the reason. See my previous post. Do the math.

    You can do math, right?

  12. 212
  13. 213
    Marco says:

    Barton, I am afraid Mack is a flat-earther. To quote from him elsewhere on the Net:
    “Secondly…Andrew Lacis, ( like all the rest) ,says “This puts the global-mean incident solar energy at 340.2 w/sq,m.” No it doesn’t cloudpoint.
    The 1360w/sq.m is a yearly global average, and is a bulk load which cannot be buggerised round with and divided down. You can’t just pick one instant in time and say the Earth casts a shadow , therefore this and that are calculated. The sun shines over your head also at nightime when you deal with this average. Reality is , the 1360w/sq.m IS the incident solar radiation. It should be regarded as non-directional, covering the whole globe at the TOA.”

  14. 214
    Mal Adapted says:


    Heh. Saw that, z, thanks. Of course you and know the difference between a stereotype and an actual person, but still…

  15. 215

    You know, I think I saw him posting for a while on Tamino’s blog, before Tamino wisely banned him. That was years ago. If he STILL doesn’t get the fact that Earth is not fully illuminated by the TSI on every square meter, you’re right–he’s almost LITERALLY a flat-Earther. Although a decent flat-Earther would concede that the night side, at least, was dark!

  16. 216
    Astringent says:

    Mack 208: If you are so sure that the atmosphere plays no role in warming the earth, can you explain why the moon, exposed to essentially the same solar heat flux as the earth, has an average temperature (averaged between night and day) of -77 degrees C?

  17. 217
    Hank Roberts says:

    Is Mack the same person formerly known as “Jacob Mack” here?
    The resemblance is startling.

  18. 218
    Keith Woollard says:

    I am not defending Mack, and I know there is a GHE, but Astringent @216 – there is a difference between the GHE and an atmosphere!!!

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