A New Millennial Global Surface Temperature Reconstruction

By Andy May

Nicola Scafetta has written a new paper (Scafetta, 2021) in Atmosphere on a new millennial surface temperature reconstruction. This is his latest “what if the models are accurate?” analysis. Scafetta’s idea is, let’s assume a model is correct, what are the implications?

Previously, he examined the PMOD solar model, by assuming it was correct and the Sun is invariant long-term, does this make sense? Another example, if we smooth through the urban heat island effect (UHI), do we eliminate it, or just smear it out, so the data looks better, but is just as inaccurate? In the latter post, on UHI, I wrote:

“Relative to 1940 to 1960, the original HadCRUT curve shows 0.59°C of warming and 0.48°C using Scafetta’s corrections. The UAH record shows 0.44°C. The CMIP5 climate models show 0.78°C of warming.

It is possible, according to Scafetta’s correction, that non-climatic biases may have contributed a fifth of the reported HadCRUT global warming since 1940-1960. It is also possible that the CMIP5 climate models may overestimate warming by a third. These are significant problems.”

Computer models have a downside. They can be used by those on the other side of the debate. If they lead to absurd or inconsistent conclusions, they make you look foolish. What if Scafetta assumed that the HadCRUT recent temperature record is correct? Then he further assumes that the CMIP5 (Coupled Model Intercomparison Project Phase 5) ensemble mean is correct, what does this mean for past temperatures? Do we find inconsistencies?

Scafetta did a frequency analysis of the temperature records since 1860, and reconstructions of Holocene climate and identified at least eight significant frequencies. One of these is a well-known and strong millennial signal, which is often associated with the Eddy solar cycle. This is the oscillation that probably caused the Medieval Warm Period (MWP) and the Little Ice Age (LIA). We can presume that these oscillations are natural and are probably due to variations in solar output. Javier has discussed the evidence for the millennial cycle or oscillation and says:

“Within the paleo-climatological scientific community there is widespread acceptance of millennial cycles during the Holocene because their effects are observed in most climatic proxies, and there is ample agreement over certain periodicities that come out of frequency analysis and are in phase from multiple proxies at different locations.”

It is well known, but poorly understood, that natural climate variability is composed of natural oscillations. Examples are the Atlantic Multidecadal Oscillation (AMO), the El Nino Southern Oscillation, the Pacific Decadal Oscillation (PDO) and others. These, and many others, have been observed, but never explained to everyone’s satisfaction. As a result, the magnitude of their effect on our climate is unknown and the CMIP5 global circulation models (GCMs) do a poor job of simulating them. It goes without saying that if we cannot measure natural variability in climate, we cannot compute the human influence on it. We have a temperature record of unknown accuracy, models of unknown accuracy, and natural climate oscillations we don’t understand, what are we to do?

Scafetta assumes the HadCRUT4 temperature record is accurate. Then, he models it as a function of the stronger observed climate oscillations, records of volcanic eruptions, and anthropogenic influences. His analysis of the model results suggests that the natural climate oscillations provide about half of the warming seen from 1970 to 2000, when the AMO was in a warm phase. When the various shorter (70 years or less) oscillations are combined, they result in a ~60-year climatic oscillation that is evident in historical, archaeological, and paleoclimatic data for many millennia. Figure 1 shows the HadCRUT4 record (blue) and Scafetta’s model in red. The model shown uses a computed anthropogenic input based on the CMIP5 models, but while they use an assumed climate sensitivity to CO2 (ECS computed from the CMIP5 ensemble model mean) of ~3°C, Scafetta uses 1.5°C/2xCO2 to accommodate his estimate of natural forcings.

Figure 1. HadCRUT4 in blue and Scafetta’s model of it in red. This is from Figure 4 in his paper. The HadCRUT4 data stops in 2013 as a test. Notice Scafetta’s model accurately reproduces the 2016 and 2020 peaks in temperature. See his paper for more details on the model. Scafetta seems to also have predicted the sudden drop in temperatures seen at the end of 2020 and the beginning of 2021.

Next, he extends the CMIP5 models back in time with data from a reconstruction of climate forcings by Thomas Crowley (Crowley, 2000). The reconstruction depends on both Crowley’s data and the CMIP5 models of the anthropogenic, volcanic and solar “forcings.” The extension to 1000AD is shown in Figure 2, where the blue line is Scafetta’s CMIP5 extension and the pink line is the CMIP5 multi-model mean. The CMIP5 solar radiation model is shown in red and the same model extended into the past is shown in black, basically the models assume that the Sun hardly varies over the long-term.

Figure 2. The CMIP5 temperature anomaly in purple and the matching solar signature in red. Scafetta’s extension of the CMIP5 model is shown in blue and the matching solar signature in black.

In Figure 3 we compare the results to the Moberg, et al (Moberg, Sonechkin, Holmgren, Datsenko, & Karlen, 2005) temperature reconstruction from 1000AD.

Figure 3. The Moberg reconstruction is shown in red, the CMIP5 extended temperature record is shown in light blue, the CMIP5 multi-model mean is shown in dark blue and the HadCRUT4 record is shown in green.

Clearly, the CMIP5 model does not successfully capture the Medieval Warm Period (MWP). There was no significant difference in volcanic activity, land use, or in CO2 or other greenhouse gas concentrations, and these are what drive the CMIP5 models. As you can see in Figure 4, from the IPCC AR5 Synthesis Report (page 6), the CMIP5 models assume that natural variation and internal climate variability are zero. So, they have no way to compute the MWP warming shown in Figure 3.

Figure 4. The factors that drive the CMIP5 climate model results. Natural forcings, such as solar variations, and internal variability, the oceans, are assumed to net to zero on climatic time scales.

The assumptions shown in Figure 4 work OK after the Little Ice Age (LIA). This is probably because the natural forcing is trending upward in a similar fashion to the CO2 concentration. By assuming that the Sun is invariant, they can assign all the warming to CO2. This assumption, that there is no natural variability over long periods of time, leads the IPCC to the mistaken assumption that ECS is 3°C/2xCO2. This assumption breaks down in the MWP.

Solar variability cannot be proven to have caused the MWP, but there is little else that could have caused it. Here, by solar variability, we mean the amount of solar radiation reaching the Earth, especially the Earth’s surface. The radiation reaching the Earth’s surface could vary because the Sun varies, as stars like the Sun do. Or it could be due to other, natural astrophysical effects, such as, variations in the solar wind, cosmic rays, or the orbits of the Moon or other planets.

Summary and Conclusions

The millennial oscillation has been very persistent throughout the Holocene Epoch, or the past 12,000 years. It gave us the Roman Warm Period, the Dark Ages, the Medieval Warm Period, the Little Ice Age and the Modern Warm Period. The Modern Warm Period is also, at least partially, influenced by some human contribution. However, Scafetta thinks that, at least 50% of the warming since 1950 is natural. Figure 5 shows Scafetta’s final semi-empirical model in blue, Moberg’s reconstruction in pink, and HadCRUT4 in red.

Figure 5.Scafetta’s model in blue, Moberg’s reconstruction in pink, HadCRUT4 in red and the CMIP5 extension (greenhouse gases, aerosols, and volcanic eruptions) in black. The black curve is moved downward for clarity.

Scafetta’s semi-empirical model is generally consistent with Moberg’s reconstruction but shows a colder Little Ice Age.

In general, Scafetta’s model shows us that the CMIP5 models are missing important climatic “forcings” or mechanisms. The smooth nature of the CMIP5 ensemble mean suggests that the CMIP5 models are not modeling the short-term climate oscillations and the mismatch with the Medieval Warm Period shows they are not modelling the longer-term oscillations either. Basically, CMIP5 is ignoring nature.

Nothing really has changed since the time of Guy Callendar or the second IPCC report, called “SAR.” The original draft of SAR Chapter 8, which was changed from the original, by politicians, contained the following statement:

“we have no yardstick against which to measure the manmade effect. If long-range natural variability cannot be established, then we are back with the critique of Callendar in 1938, and we are no better off than Wigley in 1990.” (Lewin, 2017, p. 277)

Guy Callendar was the first to use empirical data to compute the temperature effect of adding CO2 to the atmosphere. One of the major criticisms of his work was how did he know? If you don’t know the natural climate variability, how can you compute the impact of CO2? This was also the criticism that Tom Wigley faced when he was working on similar calculations for the chapter on the detection of the greenhouse effect for the first IPCC report, “FAR,” in 1990. The criticism is still valid today.

Works Cited

Crowley, T. (2000). Causes of Climate Change Over the Past 1000 years. Science, 289(5477). Retrieved from https://science.sciencemag.org/content/289/5477/270.abstract

Lewin, B. (2017). Searching for the Catastrophe Signal. Global Warming Policy Foundation. Retrieved from https://www.amazon.com/Searching-Catastrophe-Signal-Origins-Intergovernmental/dp/0993118992

Moberg, A., Sonechkin, D., Holmgren, K., Datsenko, N., & Karlen, W. (2005). Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data. Nature, 433, 613-617. Retrieved from https://www.nature.com/articles/nature03265

Scafetta, N. (2021). Reconstruction of the Interannual to Millennial Scale Patterns of the Global Surface Temperature. Atmosphere, 12(2). Retrieved from https://www.mdpi.com/2073-4433/12/2/147

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Weekly_rise
February 3, 2021 2:23 pm

I’m curious as to why Scafetta’s “CMIP5 Extension” looks so very different from Crowley, 2000’s model response, which it is purportedly replicating:

comment image

Crowley shows excellent agreement with reconstructed temps. The only note I can offer is that Scafetta’s modeled response doesn’t seem to actually reflect solar forcing, it looks like it might be the sum of just volcano+GHG’s, and looks nothing like the solar+volcano model from Crowley, Fig 3B:

comment image

Weekly_rise
Reply to  Andy May
February 3, 2021 3:43 pm

Andy, the graphs are not my own, they are screenshots from Crowley, 2000. We might suppose Crowley did not include the later reconstructions because he is not a time traveler.

But your comment doesn’t address my actual question, which is why does Scafetta’s modeled response apparently not include solar forcing? That seems like an important component to include, and it is the solar component that brings Crowley’s modeled response into agreement with the reconstruction.

I’m asking in earnest, I don’t know the answer.

Weekly_rise
Reply to  Andy May
February 3, 2021 4:37 pm

There is a pretty huge difference between saying the sun doesn’t vary significantly enough to explain the observed modern warming trend and saying solar input is an unwavering constant across all timescales and should be excluded from response models. Nowhere does the AR5 claim solar forcing should be excluded. Clearly the solar component is necessary to explain the change across the late Holocene, as shown in Crowley, 2000. There is no justification for its exclusion, as Scafetta does.

Can you cite specifically where the IPCC says the sun is constant at all timescales? Or at >1 kyr timescales?

Weekly_rise
Reply to  Andy May
February 3, 2021 6:12 pm

I believe that graphic is only attributing warming post-1950 to anthropogenic forcing, but solar activity was trending down slightly during this period, as shown in Crowley’s model, which is why the IPCC does not attribute any significant positive forcing to it. The IPCC is not here saying that solar forcing is nonexistent or negligible on all timescales, just that it wasn’t a driver of warming for the past several decades.

comment image

Last edited 2 months ago by Weekly_rise
Weekly_rise
Reply to  Andy May
February 3, 2021 7:11 pm

But again, you’re missing my point: the IPCC never assumes that solar forcing plays no significant role in millennial-scale climate changes, just that the observed solar forcing over the past several decades wasn’t the primary driver of the observed warming trend. That position holds whether you are using PMOD are ACRIM.

Weekly_rise
Reply to  Andy May
February 4, 2021 6:23 am

Can you describe why you believe the Lean 1995 reconstruction is “righter” than all the others? It seems to me to be the outlier (which is also the position of the IPCC AR5). Lean herself has produced more recent estimates (*included in the graphic you shared) which are more in line with other recent estimates.

To note: the fact that Lean 1995 might be more in line with what you want to see does not make it a better reconstruction.

And, again, you’re showing me the TSI reconstructions that were used in climate simulations – this fact stands in direct contrast to your claim that the IPCC doesn’t account for solar forcing in climate simulations.

Weekly_rise
Reply to  Andy May
February 4, 2021 8:36 am

Yet again, what you’re saying to me is, “The IPCC didn’t use the TSI reconstructions I wanted them to.” But that is completely different than, “the IPCC excludes solar forcing from all simulations,” which is what Scafetta has done. Scafetta appears to have just dropped solar forcing entirely from the “CMIP5 extension” based on Crowley, 2000’s model. You can’t simply drop solar forcing and then claim the CMIP5 extension invalidates CMIP5 because it can’t explain paleoclimate reconstructions. Of course a model of volcanic forcing will not explain MWP warmth.

And that is aside from the fact that you can’t simply append the modeled response series from Crowley, 2000 to the CMIP5 ensemble and claim you’ve extended the CMIP5 experiments back across the late Holocene, and then claim you’ve invalidated the CMIP5 if the modeled response series divergences from the reconstruction (that you seemingly have cherry picked from the available suite of paleoclimate reconstructions).

The paper seems to get messier the more I wrap my head around what exactly has been done. I’m not sure how it passed peer review in its current state.

Last edited 2 months ago by Weekly_rise
Weekly_rise
Reply to  Andy May
February 4, 2021 11:27 am

“Weekly_rise, The IPCC only uses solar reconstructions that are invariant over climate time scales.”

This is simply untrue, based on the graphic you yourself provided above. There is substantial variability in the reconstructions of solar forcing over the late Holocene. It is also untrue that Crowley, 2000, uses an invariant solar forcing. You can see in Fig 3 from Crowley that the volcano+solar series is markedly different than the volcano-only series, and it is the volcano-only series that Scafetta chooses (or rather some variant of the volcano+GHG series), with no justifiable explanation.

Fig 3:
comment image

And, again, please see the second paragraph in my comment above. Scafetta’s approach to “back-casting” the CMIP3 ensemble by appending Crowley’s modeled response series and then making proclamations about the skill of the CMIP5 appears to be completely invalid to begin with, whether Scafetta is using the appropriate data from Crowley or not.

Last edited 2 months ago by Weekly_rise
Weekly_rise
Reply to  Andy May
February 5, 2021 1:24 pm

You might think the reconstructions don’t show enough variability, but that is not an adequate justification for claiming that the solar forcing has 0 impact on model simulations and then simply dropping the solar component out of the model response series that you’re claiming represents the simulations, as Scafetta has done. Clearly the solar component has a substantial impact on the forcing. You’re trying to frame the argument as being about which solar reconstruction is the most suitable, but in fact any of the reconstructions are more suitable than Scafetta’s choice of simply using none at all.

And, again, not to sound like a broken record, but please read/address my comment above about this entire exercise of “backcasting” the CMIP5 ensemble by appending the model response series. It does not seem to me to be a sound approach and this fact would invalidate Scafetta’s entire argument.

February 3, 2021 2:31 pm

The extension to 1000AD is shown in Figure 2, where the blue line is Scafetta’s CMIP5 extension

Looks to me like a hockey stick.

CMIP5 models, but while they use an assumed climate sensitivity to CO2 (ECS) of ~3°C
CMIP5 models do not use any assumed climate sensitivity.

The smooth nature of the CMIP5 ensemble mean suggests that the CMIP5 models are not modeling the short-term climate oscillations

No, it suggests that they are an ensemble. They have oscillations, but not in phase. That is well known, and reflects what we know of Earth, where we don’t know what determines the phase either.

Reply to  Andy May
February 3, 2021 4:10 pm

Andy,
You keep asserting, without any evidence or substantiation, that the models assume a sensitivity. That is a specific complaint, and a lie. Here you even refine it to say that they assume 3°C per doubling. Where on earth do you get that from? You made it up.

Reply to  Andy May
February 3, 2021 6:05 pm

Andy,
He speaks of ECS evolution. It is something the model calculates. It isn’t an assumption.

Again, your statement is specific. ECS is assumed, and now you give a specific figure. But you can’t provide any substantiation of that claim. Models are structured. If ECS is assumed, it would be shown as an input. That can easily be searched for. And it just isn’t.

Reply to  Andy May
February 3, 2021 7:42 pm

Andy
I don’t think that is ambiguous.”
No, it isn’t. Read again the part you bolded:
whenever important changes in climate sensitivity are found

If they have assumed ECS, how could they “find” a change. It is an output, used here as a diagnostic. 

If the temperature of your cooling water rises, you should retune the engine. That doesn’t mean you assumed a temperature to get the car started. It’s just something you watch in the output.

Dave Fair
Reply to  Nick Stokes
February 3, 2021 8:14 pm

Nick, you exhibit one of CliSci’s more odious traits: You deny the documented modeling practice of tuning a model to get an ECS “that seems about right,” by obfuscating it with comments that “ECS is not a model input;” trivially true, but a lie on the face considering what is under discussion. Modelers input ECS into their models; the models don’t miraculously generate ECS.

Rory Forbes
Reply to  Dave Fair
February 3, 2021 8:50 pm

No, no, no, no … models are sentient, don’t you know? ECS doesn’t need to be an input because the models are able to determine the truth and arrive at an appropriate ECS from the given data.

Reply to  Dave Fair
February 3, 2021 8:55 pm

You deny the documented modeling practice of tuning a model to get an ECS “that seems about right,””
How about some links to that “documentation”? In fact the paper Andy quoted from was written because:
Our EC-Earth model also shows an increased sensitivity: EC-Earth2 (hereafter ECE2), which was used for CMIP5, had an ECS of 3.3K that has increased to 4.3K in the newer model version EC-Earth3 (hereafter ECE3) that is used for CMIP6. The goal of this study is to identify and quantify the contributions of model updates when going from ECE2 to ECE3.”

They aren’t trying to undo the change. They are trying to understand why it happened. That would not make sense if it happened because they had changed their assumption. As they say:
Despite the simple definition of the ECS, it is not easy to constrain its value with observations or models
It would be easy if you just assumed it.

Mike
Reply to  Nick Stokes
February 3, 2021 5:47 pm

You keep asserting, without any evidence or substantiation, that the models assume a sensitivity. That is a specific complaint, and a lie”

How can you make a predictive model without assuming an ECS – if you assume one exists?

Weekly_rise
Reply to  Mike
February 3, 2021 6:19 pm

ECS is an output of climate models; it is the thing you’re trying to get at in the first place.

Last edited 2 months ago by Weekly_rise
Mike
Reply to  Weekly_rise
February 3, 2021 6:45 pm

A predictive climate model is supposed to predict future climate. To do that you must assume an ECS…. if you believe one exists.

Read it again….”Maintaining a well-tuned model version and concurrently having a continuous overview of the ECS evolution and the main feedback parameters over time will support us in the critical evaluation of any new model developments and will suggest a critical retuning of the model whenever important changes in climate sensitivity are found.

Last edited 2 months ago by Mike
Weekly_rise
Reply to  Mike
February 3, 2021 7:39 pm

ECS is the future climate state attained following a doubling of CO2 – it is something the models calculate (i.e. it is the predicted future climate state). You can read more about the topic here:

https://www.carbonbrief.org/explainer-how-scientists-estimate-climate-sensitivity

Rory Forbes
Reply to  Weekly_rise
February 3, 2021 8:56 pm

An experiment tests an hypothesis to predict reproducible results … in other words science.

A model tests the validity of an algorithm used to projected a range of possible outcomes … prognostication. You get to pick the outcome you prefer,

Derg
Reply to  Weekly_rise
February 3, 2021 11:37 pm

MC ^2 = a range of E 🤔

Weekly_rise
Reply to  Derg
February 4, 2021 6:40 am

There would certainly be a range of E if there was uncertainty in M or C. But you do nicely point out that E is the quantity being solved for – we don’t feed it into the lefthand side of the equation.

Jim Gorman
Reply to  Weekly_rise
February 4, 2021 7:16 am

And I suppose that the “calculations” are never “tuned” to provide the “expected value”. One does not have to simply assign an ECS as a constant in order to tune. Give these guys some credit in using code further down that is tuned to provide a correct answer. That is, “well maybe this equation isn’t quite right in the way it uses the input from another equation”.

lee
Reply to  Weekly_rise
February 3, 2021 10:20 pm

If it is an output why is it listed as an input?
https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter09_FINAL.pdf Table 9.5

Reply to  lee
February 4, 2021 5:47 am

why is it listed as an input?”
It isn’t listed as an input. The caption to the table begins:

Table 9.5 | Effective radiative forcing (ERF), climate sensitivity and climate feedbacks estimated for the CMIP5 AOGCMs

You don’t have to estimate inputs; you know them. The numbers here are from two papers which diagnose GCM output.

lee
Reply to  Nick Stokes
February 4, 2021 6:36 pm

And the reason they vary? The underlying assumptions.

Weekly_rise
Reply to  lee
February 4, 2021 6:48 am

Table 9.5 is showing sensitivity estimates from the CMIP5 experiments, not the model inputs. The caption clearly says, “ECS is calculated using regressions following Gregory et al. (2004).” The abstract of Gregory et al. 2004 says “We describe a new method for evaluating the radiative forcing, the climate feedback parameter (W m−2 K−1) and hence the effective climate sensitivity from any GCM experiment in which the climate is responding to a constant forcing.”

lee
Reply to  Weekly_rise
February 4, 2021 11:16 pm

And the numbers vary because? They rely on assumptions. :0

Weekly_rise
Reply to  lee
February 5, 2021 6:15 am

Rather, there is a range in ECS because there is uncertainty about the components of the system being modeled. That does not make ECS an input to the models.

Dave Fair
Reply to  Nick Stokes
February 3, 2021 8:06 pm

And the actual model-builders say “we adjust parameters until we get an ECS that seems about right,” or thereabouts.

Reply to  Andy May
February 3, 2021 4:07 pm

You said that ” the CMIP5 models are not modeling the short-term climate oscillations”. I said that they do, but if you average an ensemble (of anything) events of different timing get smoothed out. The difference between GCMs and Scafetta is that one is ensemble averaged, the other not. 

Reply to  Andy May
February 3, 2021 7:51 pm

You can model a bell. You can describe the mechanism and frequency of the oscillations. But you can’t predict the phase. 

If you have an ensemble of bell models, they will produce a cacophany. Just like real bells, without elaborate coordination. The ensemble will not collectively produce the clear ringing that each bell can.

Rory Forbes
Reply to  Nick Stokes
February 3, 2021 9:01 pm

Therefore models aren’t competent for the important predictions, required in climate science. Projections simply have no practical use, especially with climate. With a projected range of ECS from 1.5C – 4.5C you’re not really doing anything. It’s not science. It’s just bad guesswork.

If I was to say your salary will be somewhere between $20K and $60K annually, depending on my whim, I doubt you would jump at the job.

Last edited 2 months ago by Rory Forbes
Derg
Reply to  Nick Stokes
February 3, 2021 11:40 pm

Geez dude you be-clown yourself more and more each day.

Jim Gorman
Reply to  Nick Stokes
February 4, 2021 7:40 am

“I said that they do, but if you average an ensemble (of anything) events of different timing get smoothed out.”

Hallelujah! We finally have a convert to the criticisms of Global Average Temperature!

NS is basically describing the effect that averaging has on variance. It smooths the variance out until you can no longer tell what the range of actual values may have been. In addition, it is impossible to “reconstruct” the parts that make up the whole.

It also “hides” the uncertainty of the very measurements used to make up the final value. It is why Dr. Pat Franks assessment of uncertainty for the GCMs came out so high.

This is one reason that time series analysis is more applicable than simple averaging and then calculating a simple regression.

lee
Reply to  Nick Stokes
February 3, 2021 10:17 pm

Nick, I suggest you look at Table 9.5 Row 4. It clearly says “Equilibrium Climate Sensitivity”. The table gives a range of 2.1 to 4.9. Those to me are assumptions.

David A
Reply to  Andy May
February 4, 2021 3:53 am

And Andy, it has been that way for well over a decade now. If the goal was to reflect the real world, the scary yet politicaly useful, always wrong to the observations models, would have been rejected long ago.

Yet here we are, about two decades later, still writing stories to frighten the Greta’s of the world, based on clearly wrong models that fail to reflect, not only the current observations, but also fail to manifest known past warm periods like the MWP, and we are still tuning the real world observations to cling to the scary stories!

Last edited 2 months ago by David A
Reply to  lee
February 4, 2021 5:50 am

Those to me are assumptions.
They are actually just numbers estimated. The caption to the table begins:

Table 9.5 | Effective radiative forcing (ERF), climate sensitivity and climate feedbacks estimated for the CMIP5 AOGCMs

You don’t have to estimate inputs; you know them. The numbers here are from two papers which diagnose GCM output.

Reply to  Andy May
February 4, 2021 3:05 pm

Andy,
“everyone knows ECS is not a model input. I certainly never said that”

Well, you said, and I quoted it:
” The model shown uses a computed anthropogenic input based on the CMIP5 models, but while they use an assumed climate sensitivity to CO2 of ~3°C…”
You “clarified” by saying that number was
“(ECS computed from the CMIP5 ensemble model mean)”
but that makes even less sense. Who can use the model mean in running a program? What about a model with an ECS outcome of 5°C? Did they “use” 3°C? or 5°C? In fact they wouldn’t have known the model mean before they reported.

Graemethecat
Reply to  Nick Stokes
February 4, 2021 12:55 am

From an admittedly superficial reading of this paper I get the impression that none of the existing models can reproduce past climatic excursions such as the MWP and the LIA. Is this the case? If so, how can any anthropogenic contribution be detected?

Why are we even bothering with climate models?

Richard Page
February 3, 2021 2:37 pm

Comes back to what has been said again and again – until we understand more about the natural climate variability computer models are just complete nonsense and a waste of both time and money.

Last edited 2 months ago by Richard Page
Joel O'Bryan
Reply to  Richard Page
February 3, 2021 6:07 pm

Unless it is your comfortable paycheck and paychecks and careers of those around you who feed off your grants (university overhead feeders, etc) on the line should you admit that truth publicly.
And if you don’t do it (produce junk science to meet a political agenda) then the climate scammers will find someone who will for your nice paycheck whilst you go re-train to install solar panels (h/t: J Kerry). Which is how they got the job in the first place.

Last edited 2 months ago by joelobryan
Steve Taylor
February 3, 2021 2:49 pm

Figure 1. HadCRUT4 in blue and Scafetta’s model of it in blue.

Scafetta in RED ?

Joel O'Bryan
Reply to  Andy May
February 3, 2021 6:15 pm

1 will do.

Gyan1
February 3, 2021 4:31 pm

The suns output doesn’t vary much but the amount of solar radiation reaching the surface due to variations in cloudiness dwarfs the human forcing.

https://file.scirp.org/Html/22-4700327_50837.htm

“The reduction in total cloud cover of 6.8% means that 5.4 Wm−2 (6.8% of 79) is no longer being reflected but acts instead as an extra forcing into the atmosphere,”

Joel O'Bryan
Reply to  Gyan1
February 3, 2021 6:04 pm

Lindzen’s Iris Hypotheis

Gyan1
Reply to  Joel O'Bryan
February 3, 2021 7:22 pm

Data from NASA shows that a majority of modern warming was from fewer clouds. 3 other papers put the increase at 2.8, 3.5 and 8W/m-2. NASA still cites the summary for policy makers lie that it is mostly anthropogenic rather than their own data.

Joel O'Bryan
Reply to  Gyan1
February 3, 2021 7:39 pm

The Iris Hypothesis says that the warming was the Iris (clouds) responding to the 60s-70s cooling.

Gyan1
Reply to  Joel O'Bryan
February 3, 2021 7:45 pm

Fewer clouds lasted at least until 2012.

David A
Reply to  Gyan1
February 3, 2021 10:20 pm

…and stronger El Ninos until even more recently.

David A
Reply to  Gyan1
February 3, 2021 10:17 pm

There are other large unknowns here as well. While TSI varies little, solar wavelength varies considerably, and this can be multi year, and even multi decadal variations.

The wavelength flux may very well affect cloud formation, as well as the amount of surface insolation entering the oceans, and the residence time of said energy entering the oceans.

As solar insolation penetrates up to 800′ into the oceans, even a relatively small change in wavelength insolation can, over a long ocean residence time and long term solar flux, lead to significant acumalated below the surface energy, positive or negative.
This may manifest as warmer or cooler ocean currents in well known Atlantic and Pacific patterns.

Gyan1
Reply to  David A
February 4, 2021 1:31 pm

The thermal inertial of the oceans appears to be fairly long with the PDO and AMO holding on to warm phases.

Unknowns are the reason the definitive claims about future warming are pseudoscience.

Ron Long
February 3, 2021 5:00 pm

Playing down the Medieval Warm Period, so it was not as warm as today, is countered by the fact that wine grapes were grown in northern England and they are not there today. Likewise the warming of the Little Ice Age, when Ice Fairs were held on the River Thames. I would like to see more Archaeology rolled into climate reconstructions.

Joel O'Bryan
Reply to  Ron Long
February 3, 2021 5:59 pm

Not just grapes in northern England. It bears constant repeating that the Medieval Warm Period has conclusively been shown to have been a global phenomenon in both the NH and sH, from Europe to the Americas to Asia. The Climate Scammers have consistently tried to erase it and the LIA from climate proxies, but the Anthropological evidence for the MWP and LIA is just far too strong. And their attempts paints the paleotemp proxy reconstructors who try to erase them as the science frauds they are.

Last edited 2 months ago by joelobryan
Pat from kerbob
Reply to  Joel O'Bryan
February 3, 2021 6:49 pm

Just received my copy of “A cultural history of Climate”.

Looking forward to it

Bill13
Reply to  Pat from kerbob
February 4, 2021 5:46 am

Just placed an order for this, thanks for mentioning it!

Graemethecat
Reply to  Ron Long
February 4, 2021 12:57 am

Marxists have always tried to erase History and Culture.

Reply to  Ron Long
February 4, 2021 6:13 am

Oh, ye gods! If there is one branch of pseudosciencery more obsessed with their own backsides than climastrology, it must be archaeology. Every single one of them is sure he found the definitive origins of civilisation by ascribing religious significance to every pot shard and scratched rock. Last I saw, they found Hebrew messages inked onto Mesopotamian cuneiform clay tablets… Inked, I tell you.
Please, please lord, don’t get the archaeologists involved in this new religion, I don’t think I will survive all that sighing and eye-rolling! And the splitting of the sides, oy vey, the hurting splitting of the sides!
Don’t we spend enough time insulting each other over guesstimates and models based thereupon? ECS indeed.
Thank goodness my government just allowed alcohol sales again, I would not have survived this comment section without it.
More seriously: All the graphs depict “anomalies”. Anomalous to what, exactly? Just asking.

Last edited 2 months ago by paranoid goy
Joel O'Bryan
February 3, 2021 5:49 pm

Scafetta schmetta….ppppfffftttt!

It’s all about “climate justice” for Climate Change true believers now. Not only is NO science required for them now, any science now is just a distraction for their agenda.

That is whereas science is a self-correcting process, today’s climate consensus science is a political agenda-affirming process.

John Robertson
February 3, 2021 6:18 pm

Temperature variation in 0.1C graduations..When we cannot honestly measure the current area temperature to that accuracy today,but we can know what this imaginary measure was 1000 years back?
Now I am assuming this “temperature anomaly” is that same old bugbear,the “Average Global temperature”.
So a whole bunch of words to speculate on “changes in Temperature” for which we enough information to honestly say only”We don’t know”.

I have decided to label this year 2021 as ” The International Year of Lying.”
As we are awash in nonsense and the political slime have returned to pushing the Cult of Calamitous Climate,promote a continuous public health emergency,over a virus with a 99.8 survival rate and full on censorship of any citizenry who mock the mass hysteria .

It is a real shame that Hubert Lambs work died with him,it would be very nice to have an accurate scientific estimate of past climate..instead of the policy based gunk created at the Climate Research Unit..

You know one of those carefully researched guesses listing the data and error bars..we used to expect with any science based speculation.
As another anniversary of Climate Gate fades into the past..does anyone have a copy of the promised data?
that “lost” (accidentally erased) data that was to be recreated in just 3 years…21 years ago.

fred250
February 3, 2021 8:10 pm

I’ll ask again, because I still have not got an answer from anyone..

Which climate model(s) show similar temperature to now in the 1940s, in the Arctic region?

Burl Henry
February 3, 2021 8:44 pm

Andy May:

You state “Solar variability cannot be proven to have caused the MWP, but there is little else that could have caused it”

And “The millennial oscillation…….gave us the Roman Warm Period, The Dark Ages, the MWP, the LIA, and the Modern Warm Period”

No, the MWP was clearly due to a dearth of Volcanic eruptions, only 30 VEI4, or larger, eruptions in 300 years. And the LIA was caused by a large increase in volcanic eruptions, as proven by the Central England Instrumental temperatures Data Set, where every temperature decrease correlates with a volcanic eruption, with the 1727-1739 warm period having no eruptions.-

Examination of the other periods show that their temperatures were also driven by volcanic eruptions.

Scaffeta’s paper is nonsense.

Graemethecat
Reply to  Burl Henry
February 4, 2021 1:04 am

Mount Paektu, on the border between North Korea and China, erupted at the start of the MWP in a VE7 event. Wikipedia has a good article on it.

Burl Henry
Reply to  Graemethecat
February 4, 2021 6:49 am

Graemethecat:

Yes, but it should not be considered to be part of the MWP. The next eruptions (Tolbachik.and Bezymianny) occurred 4 years later, and the next one, Vesuvius (968), occurred 18 years later. This was the pattern throughout the MWP.: An eruption, followed by many years of clean air, with no Volcanic aerosol pollution.in the atmosphere..

Burl Henry
Reply to  Andy May
February 4, 2021 7:07 am

Andy:

“This is not true”

No, it IS true..With only 30 eruptions in 300 years, there were many long intervals with no atmospheric pollution, For a VEI4, the air clears in about 18 months, and a for a VEI5, about 30 months. Even in modern times,,when there are intervals of no volcanic eruptions, temperatures rise.

There is no evidence of any solar variability, as Scafetta surmises., .

Burl Henry
Reply to  Andy May
February 4, 2021 10:35 am

Andy May::

It is IMPOSSIBLE to determine ANY variations in past solar activity by ANY proxy measurements, because of the interference of SO2 aerosols circulating i n the atmosphere

The best that can be done is to identify periods where volcanic activity has increased or decreased.

Only since the era of satellite imagery, above the atmosphere,has it been possible to observe solar variability. ,

I am sorry, but your reference to solar variability has no basis in fact.

John Tillman
Reply to  Burl Henry
February 4, 2021 7:55 am

https://www.pnas.org/content/110/42/16742

Another big eruption in AD 1257.

John Tillman
Reply to  John Tillman
February 4, 2021 8:34 am

Thus, there were at least two VEI 7 eruptions in the MWP, but only one in the LIA, towards its end, ie Tambora, 1815.

The number of VEI 6 eruptions in the two intervals is about the same, given: MWP from ~900 to 1350 and LIA from ~1350 to 1850. Cool periods suffer repeated, long solar minima, like the Maunder.

The Dark Ages Cool Period, ~450 to 900, suffered only four VEI 6 eruptions, but there was a 7 in 431. The cause of “the worst year to be alive”, AD 536, has yet to be identified, but an Icelandic or tropical eruption have been suggested, but also an extraterrestrial explanation.

Burl Henry
Reply to  John Tillman
February 4, 2021 10:55 am

John Tilman:

It largely depends upon what dates one chooses for the start of the MWP, and the start of the LIA.. It began warming up AFTER the 946 eruption, and ended in 1257, the start of the LIA, so neither belongs within the MWP..

However, there was a VEI7? eruption in 1000?, but such an eruption after the prior 30 year warming period probably did no even cause an El Nino.

Burl Henry
Reply to  Andy May
February 4, 2021 5:10 pm

John Tilman:

It appears from your historical references that the MWP WAS in progress earlier than noted by my reference (c.950). I will have to examine the prior volcanic activity, but would expect to see the same pattern as within the later period– volcanic eruptions separated by multiple years, allowing cleaner air and therefore higher temperatures within the intervals.

Thank you for your comment!

Burl Henry
Reply to  Andy May
February 4, 2021 8:29 pm

Andy May:

I thought that I was replying to John, rather than to you .Sorry.

You are correct that the warming began during the 800s. Between 850 and 950 there were 24 VEI4 or higher eruptions, and of these, 10 were separated by 4 years or more (5 by 10 years).

More than 50 years of pollution-free air would have melted a LOT of ice, freeing up Greenland and Iceland to settlement.

John Tillman
Reply to  Burl Henry
February 4, 2021 2:04 pm

Warming definitely began before the Korean-Chinese eruption. Nor did it end in 1257. The disastrous first half of the 14th century suffered a cyclic cool cycle within the secular warming trend, but its second half was warmer, such that some don’t start the LIA until 1400.

Times were good after the Black Death. The last warm cycle of the MWP kicked in and fewer people meant more land and better bargaining position for the serfs, soon to become free peasants.

The Hundred Years War resumed in 1356 atter its break for the plague.

Burl Henry
Reply to  John Tillman
February 4, 2021 10:38 am

Yes, at the beginning of the LIA

Greg
February 3, 2021 10:00 pm

but while they use an assumed climate sensitivity to CO2 (ECS) of ~3°C,

No that is not how they work. ECS is an emergent property not an “assumed” sensitivity. However, models can be tuned to provide a wide range of climate sensitivities while still matching latter 50 years of 20th c. ( and ignoring that they don’t capture the rest ) .

So what they are doing is tuning the models to produce a result which fits their political agenda, while pretending they are not progamming it in. If you claim they are using an assumed value in the models, they can easily rebut it. You need to call out the fact the models are rigged to produce the apparent “result” of ECS.

The smooth nature of the CMIP5 ensemble mean suggests that the CMIP5 models are not modeling the short-term climate oscillations

No. The model means do not have short term oscillations BECAUSE they are model means. Averaging many models or model runs removes the short term features. Individual models may have short term oscillations but you would not see that in the mean.

Last edited 2 months ago by Greg
Richard S Courtney
Reply to  Greg
February 4, 2021 2:30 am

Andy May,

You conclude saying,

“Guy Callendar was the first to use empirical data to compute the temperature effect of adding CO2 to the atmosphere. One of the major criticisms of his work was how did he know? If you don’t know the natural climate variability, how can you compute the impact of CO2? This was also the criticism that Tom Wigley faced when he was working on similar calculations for the chapter on the detection of the greenhouse effect for the first IPCC report, “FAR,” in 1990. The criticism is still valid today.”

Yes, that “criticism is still valid today”.

Climate behaviours can be observed but it will not be possible to separate behaviour(s) of specific effects (e.g. of GHGs, of solar variation, of volcanism and of etc.) from natural climate behaviour(s) until climate variability is understood and quantified. Therefore, the only discussion of your article meriting consideration would be citation and/or presentation of determination of natural climate variability because all claims – including yours – of specific effects on climate behaviours cannot be separated from natural climate variability in observed climate behaviour(s).

Simply, you make a good and valid case which you damage by attempting to replace claimed effects of volcanoes and GHGs with your claims of solar effects.

Richard

Burl Henry
Reply to  Andy May
February 4, 2021 7:43 am

Andy May:

If you will examine my paper, “A Graphical Explanation of Climate Change” you will see that the PRIMARY natural influence affecting our climate is the amount of dimming SO2 aerosols in the atmosphere, There is also some natural warming as the climate continues to recover from the LIA (albedo changes)

http://www.skepticmedpublishers.com/article-in-press-journal-of-earth-science-and-climatic-change/

Andy Pattullo
February 4, 2021 8:17 am

Well that is all very well if you insist on the scientific approach, but what about wide-eyed, anthropocentric, self destructive, superstitious panic. Now that is a movement we can all get behind.

Bindidon
February 5, 2021 12:59 pm

Andy May

As a layman, I start with a simple question.

In Scafetta’s article, I see the following picture (I had to generate screenshots, because for some reason, the original pictures were not accessible):

https://drive.google.com/file/d/14BmIk3j3NDYxjMbagECs_6YqbkbP1Rfe/view

while your article begins with an ‘interesting’ cutout of it:

https://drive.google.com/file/d/1UaWzOE4puywClavHZa107oN2Syl_24N9/view

Did something disturb you in the original picture?

J.-P. D.

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