Reposted from Dr. Roy Spencer’s website
October 25th, 2019 by Roy W. Spencer, Ph. D.
NOTE: I have written on this subject before, but it is important enough that we need to keep thinking about it. It is also related to the forcing-feedback paradigm of climate change, which I usually defend — but which I will here take a skeptical view toward in the context of long-term climate change.
The UN IPCC scientists who write the reports which guide international energy policy on fossil fuel use operate under the assumption that the climate system has a preferred, natural and constant average state which is only deviated from through the meddling of humans. They construct their climate models so that the models do not produce any warming or cooling unless they are forced to through increasing anthropogenic greenhouse gases, aerosols, or volcanic eruptions.
This imposed behavior of their “control runs” is admittedly necessary because various physical processes in the models are not known well enough from observations and first principles, and so the models must be tinkered with until they produce what might be considered to be the “null hypothesis” behavior, which in their worldview means no long-term warming or cooling.
What I’d like to discuss here is NOT whether there are other ‘external’ forcing agents of climate change, such as the sun. That is a valuable discussion, but not what I’m going to address. I’d like to address the question of whether there really is an average state that the climate system is constantly re-adjusting itself toward, even if it is constantly nudged in different directions by the sun.
If there is such a preferred average state, then the forcing-feedback paradigm of climate change is valid. In that system of thought, any departure of the global average temperature from the Nature-preferred state is resisted by radiative “feedback”, that is, changes in the radiative energy balance of the Earth in response to the too-warm or too-cool conditions. Those radiative changes would constantly be pushing the system back to its preferred temperature state.
But what if there isn’t only one preferred state?
I am of the opinion that the F-F paradigm does indeed apply for at least year-to-year fluctuations, because phase space diagrams of the co-variations between temperature and radiative flux look just like what we would expect from a F-F perspective. I touched on this in yesterday’s post.
Where the F-F paradigm might be inapplicable is in the context of long-term climate changes which are the result of internal fluctuations.
Chaos in the Climate System
Everyone agrees that the ocean-atmosphere fluid flows represent a non-linear dynamical system. Such systems, although deterministic (that is, can be described with known physical equations) are difficult to predict the future behavior of because of their sensitive dependence on the current state. This is called “sensitive dependence on initial conditions”, and it is why weather cannot be forecast more than a week or so in advance.
The reason why most climate researchers do not think this is important for climate forecasting is that they are dealing with how the future climate might differ from today’s climate in a time-averaged sense... due not to changes in initial conditions, but in the “boundary conditions”, that is, increasing CO2 in the atmosphere. Humans are slightly changing the rules by which the climate system operates — that is, the estimated ~1-2% change in the rate of cooling of the climate system to outer space as a result of increasing CO2.
There are still chaotic variations in the climate system, which is why any given climate model forced with the same amount of increasing CO2 but initialized with different initial conditions in 1760 will produce a different globally-averaged temperature in, say, 2050 or 2060.
But what if the climate system undergoes its own, substantial chaotic changes on long time scales, say 100 to 1,000 years? The IPCC assumes this does not happen. But the ocean has inherently long time scales — decades to millennia. An unusually large amount of cold bottom water formed at the surface in the Arctic in one century might take hundreds or even thousands of years before it re-emerges at the surface, say in the tropics. This time lag can introduce a wide range of complex behaviors in the climate system, and is capable of producing climate change all by itself.
Even the sun, which we view as a constantly burning ball of gas, produces an 11-year cycle in sunspot activity, and even that cycle changes in strength over hundreds of years. It would seem that every process in nature organizes itself on preferred time scales, with some amount of cyclic behavior.
This chaotic climate change behavior would impact the validity of the forcing-feedback paradigm as well as our ability to determine future climate states and the sensitivity of the climate system to increasing CO2. If the climate system has different, but stable and energy-balanced, states, it could mean that climate change is too complex to predict with any useful level of accuracy.
El Nino / La Nina as an Example of a Chaotic Cycle
Most climate researchers view the warm El Nino and cool La Nina episodes conceptually as departures from an average climate state. But I believe that they are more accurately viewed as a bifurcation in the chaotic climate system. In other words, during Northern Hemisphere winter, there are two different climate states (El Nino or La Nina) that the climate system tends toward. Each has its own relatively stable configuration of Pacific trade winds, sea surface temperature patterns, cloudiness, and global-average temperature.
So, in a sense, El Nino and La Nina are different climate states which Earth has difficulty choosing between each year. One is a globally warm state, the other globally cool. This chaotic “bifurcation” behavior has been described in the context of even extremely simple systems of nonlinear equations, vastly simpler than the equations describing the time-evolving real climate system.
The Medieval Warm Period and Little Ice Age
Most historical records and temperature proxy evidence point to the Medieval Warm Period and Little Ice Age as real, historical events. I know that most people try to explain these events as the response to some sort of external forcing agent, say indirect solar effects from long-term changes in sunspot activity. This is a natural human tendency… we see a change, and we assume there must be a cause external to the change.
But a nonlinear dynamical system needs no external forcing to experience change. I’m not saying that the MWP and LIA were not externally forced, only that their explanation does not necessarily require external forcing.
There could be internal modes of chaotic fluctuations in the ocean circulation which produce their own stable climate states which differ in global-average temperature by, say, 1 deg. C. One possibility is that they would have slightly different sea surface temperature patterns or oceanic wind speeds, which can cause slightly different average cloud amounts, thus altering the planetary albedo and so the amount of sunlight the climate system has to work with. Or, the precipitation systems produced by the different climate states could have slightly different precipitation efficiencies, which then would affect the average amount of the atmosphere’s main greenhouse gas, water vapor.
Chaotic Climate Change and the Forcing-Feedback Paradigm
If the climate system has multiple, stable climate states, each with its own set of slightly different energy flows that still produce global energy balance and relatively constant temperatures (whether warmer or cooler), then the “forcing-feedback framework” (FFF, as my Australian friend Christopher Game likes to call it) would not apply to these climate variations, because there is no normal, average climate state to which ‘feedback’ is constantly nudging the system back toward.
Part of the reason for this post is the ongoing discussion I have had over the years with Christopher on this issue, and I want him to know that I am not totally deaf to his concerns about the FFF. As I described yesterday, we do see forcing-feedback type behavior in short-term climate fluctuations, but I agree that the FFF might not be applicable to longer-term fluctuations. In this sense, I believe Christopher Game is correct.
The UN IPCC Will Not Address This Issue
It is clear that the UN IPCC, by its very charter, is primarily focused on human-caused climate change. As a result of political influence (related to the desire of governmental regulation over the private sector) it will never seriously address the possibility that long-term climate change might be part of nature. Only those scientists who are supportive of this anthropocentric climate view are allowed to play in the IPCC sandbox.
Substantial chaos in the climate system injects a large component of uncertainty into all predictions of future climate change, including our ability to determine climate sensitivity. It reduces the practical value of climate modelling efforts, which cost billions of dollars and support the careers of thousands of researchers. While I am generally supportive of climate modeling, I am appropriately skeptical of the ability of current climate models to provide enough confidence to make high-cost energy policy decisions.
a few minutes of research shows that Roy is wrong.
the first mistake he makes is leaving TSI out of the things that drive changes in GCM.
Here is the thing. Chaos, in an of itself cannot cause long term climate change. If you do not change the energy
IN to the system, then the change will be limited to what is known as UNFORCED INTERNAL VARIABILITY.
you cannot, over the long run, create more energy in the system out of nothing.
unforced internal variability will sum to zero over time, or basic laws of physics are violated.
To get a picture of unforced variability you do control runs. you hold all forcings constant
( the sun, ghgs, aerosols) and you let the model run. YOU STILL GET CHANGES ( because) chaos
But over time those changes sum to zero.
What kind of changes? things like El nino
https://link.springer.com/article/10.1007/s00382-019-04660-0
https://atmos.washington.edu/~david/Atwood_ENSO_etal_2016.pdf
https://www.nature.com/articles/s41612-018-0043-7
Steven Mosher,
You say,
“you cannot, over the long run, create more energy in the system out of nothing.”
True, but so what?
1.
You can change both the Earth’s average surface temperature and its average radiative temperature by redistributing that heat, and the oceans move much heat.
2.
Stores of energy in the system (notably, ice) can add energy to the system behaviour or remove it from the system behaviour by melting or freezing.
etc.
Richard
Mosher writes
That is an assertion, not a fact. The earth is big and not a bathtub where change is readily reflected throughout. Regional climate change over the long term is possible. We know this to be true because of archaeological evidence of Vikings in Greenland. I’m pretty sure they weren’t driving SUVs.
Please clarify this energy /mass thing. When a fossil fuel is used to create energy is produced from the mass of the fuel in the classic e=mc^2? So was the mass being converted into energy created by photosynthesis or some other natural process or are the chemical bonds mass less and in fact overall there is a mass loss?
When a fossil fuel is used to create energy is produced from the mass of the fuel in the classic e=mc^2?
No. E=MC^2 applies to splitting or fusion of atoms (nuclear bombs & reactors do this).
Burning fossil fuels breaks up molecules, not atoms. The energy released by breaking up molecules and attaching them to different molecules (CH4 => CO2 + 2x H2O) releases energy, but doesn’t change mass.
Steven
With an ocean system that can store and release massive amounts energy on times scale of thousands of years you don’t need a change in input to have long term global variations in temperature that are in fact relatively small in comparison to the mean energy state of the system. What you see as Global Climatic change is a rounding error.
Mosher,
Roy’s full comment was
“The UN IPCC scientists who write the reports which guide international energy policy on fossil fuel use operate under the assumption that the climate system has a preferred, natural and constant average state which is only deviated from through the meddling of humans. They construct their climate models so that the models do not produce any warming or cooling unless they are forced to through increasing anthropogenic greenhouse gases, aerosols, or volcanic eruptions.”
I.e not changing the TSI
“what happens when you hold everything constant? YOU STILL GET SOME CHANGE.”
To run a computer programme you need to introduce changing elements, one is called time.
You can only get the possibility of change when you allow a change in some variable to occur.
I’m Hans Brinker (of the silver skates, you know, that guy!). Please bring back the “little ice age”, it’s hard to skate on canals that aren’t frozen.
Thank you. Hans
Mosher
The AR5 IPCC Forcings bar graph for the period 1750 to 2011 shows an increase in Anthropogenic Forcings of 2.29 W/M2 (1.13 to 3.33) and all natural Forcings, in this case identified as solar, are said to have added only 0.05 W/M2 in this period.
Internal variability is then said to explain all other temperature change.
It is not hard to remove the Anthropogenic Forcings from our best temperature series and see what is left.
I have done this exercise out of interest. The result shows internal variability adding significantly to global temperature for 50 years followed by a precipitous drop after about 1990.
The result looks unlikely to me.
Dr. Spencer mentions chaotic system and feedback mechanisms, which some may use to try to explain what’s going on.
Which reminded of in the 1980s, when Chaos Theory became the buzz. “Fractals” and chaos stuff was applied to most anything. Within this was the “Butterfly Effect”, whereby a butterfly flapping its wings in the tropics would eventually set off a storm in the Atlantic.
Fascinated readers may chose their area, but the theory made headlines and employed writers.
“Chaos” and “Fractals” were even applied to the financial markets. As in stocks, bonds, currencies and commodities.
Serious financial researchers were trying to forecast trend and trend changes using Chaos Theory.
At the time, the only concept that seemed worthwhile was “Constrained Randomness”.
And, it is a good explanation for the history of financial markets and climate.
On the latter, there has been very long-term trends, such as the current interglacial.
Within this there has been some weather extremes.
Like Vancouver suffering its first frost on October 5th, when the typical is a month later.
“Like Vancouver suffering its first frost on October 5th”
We haven’t had frost yet this fall in the Vancouver region. We did have record lows however( +1C ). My weather app is predicting freezing overnight temperatures for tuesday, October 29. I will finally have to bring some of my plants indoors for the winter).
Our lawn sprinkling restrictions don’t end until the end of the month. The restrictions keep getting extended for pure propagandist reasons.
Roy, consider for a moment that any equilibrium is a balance of at least two forces. Call them X2 and Y2 ( my phone is not doing powers) Mathematically that is X2 + Y2 = 0. The solution to that equation is a U shaped graph (or upside down U shaped) with either a single minimum or a single maximum. I’m sure you know this
A third order equation – X3 – solves with a maximum and minimum. Stability could be seen as oscillation between them.
Radiation is a fourth order equation, X4, and those graphs have a curvy W shape, with either two minimums and a maximum or two maximums and a minimum ( for the upside down version)..
The implications should be obvious- stability oscillates around those maximums and minimums
There is more than one solution, stability point.
Does the Earth system have any concept of what climate is, what a climate state is, what an preferred average is? I would guess the Earth system hasn’t a clue what they are and just exists.
Dr Spencer’s comment about the IPCC charter being written around anthropogenic causes is perhaps key to understanding why this whole, mad CAGW thing keeps running.
It is not so much that non-anthropogenic mechanisms are or are not in evidence it is just that only anthropogenic explanations get rewarded with IPCC recognition and therefore indirectly, funding.
The great green blob is not interested in the science per see, it is ony interested in a scientific basis to blame some human entity, be that western capitalism or whoever.
Average state?
Indeed there is.
An average global mean temperature of 16.7138163421 degrees of Celsius +/- 0.00000000000000000000000000000000000000000000000001 degrees of Celsius.
Percentage atmospheric nitrogen of 77.826361616362616263748882153% +/- 0.00000000000000000000000000000000001%
Zero carbons of course.
Oxygen? We should get rid of that entirely. The stuff’s far too reactive.
I’m sure and act of parliament (or a UN diktat) will sort all that out no prob.
More taxes! That always works…….
On how nature works. Take river/stream drainage systems:
The drainage system architecture evolves to carry the seasonal variation of water flow and sediments with near maximum efficiency. Within natural waterways there are some fascinating mathematical relationships:
– On a given gradient and topography the length ratio between rapids and pools will remain similar
– The banks will overflow on average once/year
– Short of being on a fault-line or confined by a rock mass the channel will never be straight
But
The stream bed will migrate laterally over time or change its channel through erosion and deposition at the banks.
My belief is that climate is an evolved system involving all components within ecology with the purpose of moderating temperature variation with efficiency in spite of forcing variation. It will take a heck of lot more than a blip in atmospheric CO2 levels to make it even sneeze.
If my theory is right there should be a decade-scale down-trend in temperatures sometime within the next (say) 30 years. These are the cycles within a trend. There is no such thing as a straight trend. There is always a lag period while negative feedback components (e.g. plankton/vegetation) within the system build their response. I am convinced that we have little understanding yet as to what the complete negative feedback system entails.
I recall driving for several hundred KM through a flood basalt landscape in Ethiopia. Outcrops displayed up to 12 different events of up to 4 m thickness. This is just one of several traps around the world each of which probably had a activity duration of centuries. What was the impact of these throughout the globe? Hell on earth I imagine. Yet, here we are arguing about a storm in a tea cup.
The climate system has evolved. Without its inherent resilience we would not be here.
M
”If my theory is right there should be a decade-scale down-trend in temperatures sometime within the next (say) 30 years.”
”Yet, here we are arguing about a storm in a tea cup.”
Yes I agree. And therefore long term climate modelling is at present a complete joke. So much so that any discussion of them should be banned for wasting everyone’s time.
“But the ocean has inherently long time scales — decades to millennia. An unusually large amount of cold bottom water formed at the surface in the Arctic in one century might take hundreds or even thousands of years before it re-emerges at the surface, say in the tropics. This time lag can introduce a wide range of complex behaviors in the climate system, and is capable of producing climate change all by itself.”
I think Mosher missed that part of Spencer’s article, or he simply does not understand the concept.
I think Mosh has had too much EtOH tonight.
Roy Spencer – I’m not sure that this statement of yours is correct:
“If there is such a preferred average state, then the forcing-feedback paradigm of climate change is valid. In that system of thought, any departure of the global average temperature from the Nature-preferred state is resisted by radiative “feedback”, that is, changes in the radiative energy balance of the Earth in response to the too-warm or too-cool conditions. Those radiative changes would constantly be pushing the system back to its preferred temperature state.”
My understanding is that the climate models are coded with positive feedbacks – that is, that an increase (or decrease) in temperature caused for example by increase (or decrease) in atmospheric CO2 will be reinforced by ‘feedbacks”. My understanding also is that these “feedbacks” operate regardless of the cause of the initial temperature change. So, for example, they would operate equally if the original change was caused by a TSI change.
These positive feedbacks in the models appear to me to be the exact opposite of your description.
Dr. Spencer, I have long believed that there is at least a high probability that the climate system is a (multi-year-Stabilizing) Chaotic Force Feedback (SCFF) system with long time constants (long time constants are by definition – if they were short time constants we would call it “weather”). Climate scientists who say “the science is settled” are presumably denying this possibility – a denial that is fundamentally unscientific unless and until it has been studied to death.
You are precisely right to point out that the phase space diagrams point to SCFF – not least because measurables such as average temperature are remarkably stable year-to-year. If the Earth-system is so sensitive to greenhouse gas warming that 100ppm of CO2 will initiate destabilizing feedbacks, then one extra-humid summer on the East Coast would initiate destabilizing feedbacks.
What would stabilizing feedbacks SCFF look like? Almost certainly they have to do with water vapour (credit to Eschenbach for first introducing this possibility to me) because it is (a) spatially varying and (b) the only greenhouse gas strong enough to fight CO2. Atmospheric water just has to change state (liquid to gas) to shift from a reflector of incoming light (clouds) to a blocker of outgoing heat (humidity).
A period of contemplation may be required by the climate computer model enthusiasts. Can I suggest spending a summers day outside, from early morning through to dusk. Look at the sky and watch as clouds form. Watch as they come and they go all in the same portion of sky,with little to indicate what any particular part of the sky will do next. Then ask yourselves, does my much loved program have so much detail written into its code, that it can account for this chaotic completely unpredictable change in transient solar reflectivity. If the computer model has such detail, then perhaps we should pay attention to the outputs. If it doesn’t, then it is simply a toy fascinating but lacking in sufficient process detail to be of any value and unable to predict anything with accuracy.
Non-linear, highly complex systems where everything affects everything else are unlikely to have a long-term steady state, even with no changes in external inputs. They may fall into such states at random but that is simply random. How many possible combinations of each possible state of each parameter are there? Tens of billions? Trillions? The differences between each combination may be quite small when netted but each one is a different state, not a steady state – even though it appears to us to be a steady state because we measure only a few things at a gross level and quite inaccurately.
There’s no steady state, just the illusion of one because of our limitations of measurement.
There is, of course, a stable average state which climate always works back towards.
The essential outcome to sustain an atmosphere long term is to ensure that there is always sufficient kinetic energy at the surface to provide both radiation to space equalling radiation in from space and to support the mass of the atmosphere off the surface against the downward force of gravity in hydrostatic equilibrium.
If either of those conditions are not satisfied for any length of time then the atmosphere must either be lost to space or will freeze to the ground.
The mechanism for constant ongoing adjustments is variable convection which involves a combination of locally and regionally changing lapse rate slopes with the inevitable consequence of shifting climate zone boundaries.
It has long been known that to maintain hydrostatic equilibrium it is necessary for convective changes to neutralise radiative imbalances but the implications of that principle for climate have been ignored by the radiative theorists.
One need only look at the analyses by me and Philip Mulholland to verify the outcome on multiple worlds with atmospheres.
https://www.researchgate.net/project/Dynamic-Atmosphere-Energy-Transport-Climate-Model
I have been unable to post this at Roy’s site because I remain banned for life as a result of trying to politely remind him of some basic meteorology. Perhaps he might reconsider?
From a somewhat naive point of view, the answer to the question at the head of the article is a resounding yes. Is calling it preferred wrong? I would say not really as it is used to introduce a topic of learning. After all similar phraseology is used in secondary school chemistry and physics when teaching atomic structure, with the ground state being referred to as the preferred state, or the explanation of diatomic structure for all gases except the noble gases. Then there’s nature abhors a vacuum.
Personally I am of the opinion that there are multiple ground states for the climate, dependent on the multiple factors that are involved, TSI across the whole EM spectrum, orbital mechanics, plate tectonics, solar electromagnetic activity (sunspots etc) and cosmic ray interactions, then there’s adiabatic changes as well as the influences of water vapour, Carbon Dioxide etc.
Roy Spencer,
My opinion of this matter has remained unchanged for the last two decades, and during that time I have repeatedly posted that view in many places, e.g. see here
http://allaboutenergy.net/environment/item/2208-letter-to-senator-james-inhofe-about-relying-on-ipcc-richard-courtney-uk
It seems appropriate for me to post it again here.
The climate models are based on assumptions that may not be correct. The basic assumption used in the models is that change to climate is driven by change to radiative forcing. And it is very important to recognise that this assumption has not been demonstrated to be correct. Indeed, it is quite possible that there is no force or process causing climate to vary. I explain this as follows.
The climate system is seeking an equilibrium that it never achieves. The Earth obtains radiant energy from the Sun and radiates that energy back to space. The energy input to the system (from the Sun) may be constant (although some doubt that), but the rotation of the Earth and its orbit around the Sun ensure that the energy input/output is never in perfect equilibrium.
The climate system is an intermediary in the process of returning (most of) the energy to space (some energy is radiated from the Earth’s surface back to space). And the Northern and Southern hemispheres have different coverage by oceans. Therefore, as the year progresses the modulation of the energy input/output of the system varies. Hence, the system is always seeking equilibrium but never achieves it.
Such a varying system could be expected to exhibit oscillatory behaviour. And, importantly, the length of the oscillations could be harmonic effects which, therefore, have periodicity of several years. Of course, such harmonic oscillation would be a process that – at least in principle – is capable of evaluation.
However, there may be no process because the climate is a chaotic system. Therefore, the observed oscillations (ENSO, NAO, etc.) could be observation of the system seeking its chaotic attractor(s) in response to its seeking equilibrium in a changing situation.
Very, importantly, there is an apparent ~900 year oscillation that caused the Roman Warm Period (RWP), then the Dark Age Cool Period (DACP), then the Medieval Warm Period (MWP), then the Little Ice Age (LIA), and the present warm period (PWP). All the observed rise of global temperature in the twentieth century could be recovery from the LIA that is similar to the recovery from the DACP to the MWP. And the ~900 year oscillation could be the chaotic climate system seeking its attractor(s). If so, then all global climate models and ‘attribution studies’ utilized by IPCC and CCSP are based on the false premise that there is a force or process causing climate to change when no such force or process exists.
But the assumption that climate change is driven by radiative forcing may be correct. If so, then it is still extremely improbable that – within the foreseeable future – the climate models could be developed to a state whereby they could provide reliable predictions. This is because the climate system is extremely complex. Indeed, the climate system is more complex than the human brain (the climate system has more interacting components – e.g. biological organisms – than the human brain has interacting components – e.g. neurones), and nobody claims to be able to construct a reliable predictive model of the human brain. It is pure hubris to assume that the climate models are sufficient emulations for them to be used as reliable predictors of future climate when they have no demonstrated forecasting skill.
Richard
The UN IPCC scientists who write the reports which guide international energy policy on fossil fuel use operate under the assumption that the climate system has a preferred, natural and constant average state which is only deviated from through the meddling of humans. They construct their climate models so that the models do not produce any warming or cooling unless they are forced to through increasing anthropogenic greenhouse gases, aerosols, or volcanic eruptions.
Excellent article Roy, this statement is unquestionably and undeniably true. Mosher and Lloydo can deny it with all the bluster they want, but this belief in Edenic stasis is as central to contemporary popular green ideology and the existence of God is to monotheistic religion. Mosher and Lloydo are of course intelligent enough to realise that Edenic stasis is false, but they are silent and make no attempt to contradict the assumption of Edenic stasis that underlies all alarmist climate narrative.
The term “pre-industrial climate” assumes Edenic stasis, that is, that before human CO2 emissions, there was one climate, one temperature, one CO2 level, one humidity, one sea temperature, one everything.
This is where climate double speak, or Parceltongue, comes in. The scientific literature of course is filled with evidence from ice ages and all past climate, that there was never any Edenic stasis. Journalists and activists don’t read scientific papers. Or if they do, they learn climate doublespeak-parceltongue. “Le plus ca change, le plus c’est la meme chose.” The more it changes, the more it stays the same. One reality for professional science. Another one for the political narrative. Side by side in perfect harmony.
I would hazard guess that the good Dr. has acquired some uncertainty about models after Pat Frank quantified that not too long ago?
The science is not settled, rather uncertain?
The climate system has a preferred natural average determined by the distribution of insolation according to Milankovitch forcing, and this preferred state is not constant but changes so slowly that we can assume it is constant over the period of one or two centuries. What most climate scientists don’t realize is that the forcing-feedback changes to the climate system are adjusted to the preferred Milankovitch average so that the bigger the departure the stronger the feedbacks to return to it. The Little Ice Age constituted a strong departure from the preferred Milankovitch average towards the cold side, and was followed by a strong feedback-driven rebound. We are now in a strong departure from the preferred Milankovitch average towards the warm side, so growing feedbacks will act as an impediment to further warming.
Global warming is set to decelerate, not to accelerate, until a time in the future when it will naturally revert. Our effect on climate is not enough to drive the system.
“the bigger the departure the stronger the feedbacks to return to it”
If that was all there was to it then over the longer term temperature would closely correlate with the Milankovitch cycle.
The longer term temperature does closely correlate with the Milankovitch cycle
This is known since the mid-70s when δ¹⁸O was measured in benthic cores.
Same for the Holocene with multiple global proxies
Eventually temperature will return to its Milankovitch preferred state. People will like that a lot less than global warming.
You say above “The Little Ice Age… was followed by a strong feedback-driven rebound. We are now in a strong departure… towards the warm side, so growing feedbacks will act as an impediment to further warming.” In other words the system is “rebounding” over periods of decades but there are periods of tens of thousands of years with poor correlation.
Yes, we are in a strong upward departure driven by the rebound from the LIA, by a long period of above average solar activity, and by the anthropogenic effect. The rebound from the LIA was over about 100 years ago, or so. Solar activity won’t go higher that it has been during the 20th century, so it is up to the anthropic effect to fight the increasing strength of feedbacks trying to return the temperature to the preferred natural average. This means decelerating warming, not accelerating as the models say.
Nature has a preferred natural average that changes over time, but it is almost never there in a scale of centuries because of the lags and overreactions. In a scale of tens of thousands of years the correlation used to be much better, but the accumulation of extra-polar ice during glacial periods since the Mid-Pleistocene Transition was too much to be melted by obliquity forcing alone. Hence interglacials started to skip some obliquity oscillations (it can be hindcasted and forecasted which ones) and the correlation became poor, but still interglacials only happen when obliquity is high and the system can move towards its preferred natural average. The poor correlation does not indicate a lack of causal relation but the inability at certain times of the system to approach its preferred state by the massive ice build up.
Javier
If I’m not mistaken, currently (post MPR) an interglacial requires an obliquity peak – lagged by 6500 years for ocean thermal “inertia”, plus coincident peaks in eccentricity and both precession and the amplitude of precession modulation (which is practically the same thing as eccentricity). Thus – as you say – we get an interglacial every 2-3 obliquity peaks. (When an eccentricity peak is half way between two obliquity peaks then we get a double-header interglacial e.g. 200, 600 kya.) Before the MPR ~ 1 Mya, the system was easier to pull to interglacial and an interglacial happened with every single obliquity peak (after a lag).
The big picture would be that the climate system is moving slowly from hot house to ice house attractors. There is a transitional period of flicker between the two attractors that we are now in. But as the system as a whole sinks deeper into a cold place, the affinity of the warm attractor diminishes. If the trend continues the eventually we get permanent deep glaciation.
The same thing would happen when we move out of, as well as into, a period of deep glaciation. It’s been found that at the end of the Marinoan glaciation about 640 million years ago, just before (or even during) the Cambrian explosion, there was also glacial-interglacial flicker:
https://www.nature.com/articles/ngeo2502
Phil, that is what the data indicates.
But the system appears to have stabilized and the planet is not cooling further. The flickering has increased in amplitude and this results in very cold glacials and very warm interglacials. Post MPT interglacials are actually warmer than Early Pleistocene interglacials.
My opinion is that we are at the bottom of the Late Cenozoic Ice Age, and the planet will remain in this situation for a few million years before starting slowly to get out of the Ice Age, something that can take another 50 million years.
Interesting discussion and while it maybe true that, apart from when passing through tipping points and despite some noise the climate tends back towards the TSI trend.
?itok=RPG6MRlA does not support your statement: “This means decelerating warming, not accelerating…”
However this:
“Eventually temperature will return to its Milankovitch preferred state…”
Further, this has only been true for the Pliocene (apart from what Phil mentioned), liberating 1Tt of CO2 ends the Pliocene. So by “eventually” you mean when that exhaust plume has largely cleared?
Javier
Yes I remember the data you posted about the coldest point being around 200,000 years ago.
Lloydo
I think you meant Pleistocene, not Pliocene (last ~3 million years of glacial-interglacial alternation).
But a nonlinear dynamical system needs no external forcing to experience change. I’m not saying that the MWP and LIA were not externally forced, only that their explanation does not necessarily require external forcing.
This is an extremely important point.
Assuming all climate variation is from solar forcing is exactly the same mistake as assuming it is all CO2 forcing.
The nonlinear-chaotic system changes by itself with no need of external forcing.
You can also have both.
Oscillation driven by internal dynamic but entrained, in either simple or complex ways, by external periodic forcing.
An excellent article from Dr Spencer which makes a compelling and vitally important point, and to which little needs to be added.
and so the models must be tinkered with until they produce what might be considered to be the “null hypothesis” behavior, which in their worldview means no long-term warming or cooling.
Ed Lorenz In 1962 defines the null hypothesis in his paper “Deterministic Nonperiodic Flow”. A simple climate simulation in which there was no change in any external forcing, produced endless change in the climate state, in a pattern that resembled (but is not) random walk.
https://journals.ametsoc.org/doi/pdf/10.1175/1520-0469(1963)020%3C0130%3Adnf%3E2.0.co%3B2
In short – Lorenz’ discovery is the cornerstone of climate science:
For climate, change is the null hypothesis.
True Phil but look at Javier’s link from above –
You can’t tell me that spike is internal.
If that curve is true then no – the spike is unlikely to be internal.
I have tried to suggest, without success, that the idea of a long term mean temperature may not apply to the Earth for about 25 years now. Few people acknowledge it to be possible. And one may not even have to have a set of stable states to wander amongst, but just a very broad, flat extremum in parameter space in which the climate wanders, being pushed around by rather small changes to input.
With regard to variations to TSI as an input, let’s suppose it is as large as
. There is also water vapor feedback which will operate on this change to magnify it, change its phase, etc, etc. It seems there is plenty of known variability, to which one also has to add our uncertainty of the explicit factors in a model (parameterization particularly) and the uncertainty of potentially having incomplete models in the first place, to credibly estimate how well climate models should be expected to project future temperatures — or to credibly identify one factor versus another as the cause of a climate excursion.
There could just be a self obsessed species, full of it’s own self importance with the ability to make observations of it’s surroundings. They could even collate those observations that span a whole two hundred years and pretend that it somehow matters when it comes to observing the Weather.
They could even invent a whole array of fine tuned equipment dedicated to measuring and interpreting their understanding of Weather and develop an entire industry dedicated towards predicting the future.
They could classify it, spend billions of dollars devoted to predicting it, develop whole scientific classifications and denote a label for those who spend a lifetime dedicated to such endevours.
But Weather will still be Weather, and the best of the best will still struggle to predict it three days out let alone three decades out.
Thirty years on and the IPCC is still yet to get a Single thing right, Thirty years on, I can still rely upon my local Termites building new mud that Rain will arrive in the following next three weeks.
How long will this charade continue ?