New paper cuts recent anthropogenic warming trend in half

Tamino (aka Grant Foster) will have his knickers in a twist over this one.

Guest post by Marcel Crok (from his blog De staat van het klimaat)

An interesting new paper (behind paywall) has been accepted for publication in the Journal of the Atmospheric Sciences. The paper by Jiansong Zhou and Ka-Kit Tung of the University of Washington, Seattle is titled “Deducing Multi-decadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis”.

This paper will add fuel to the recent discussions about the nature of the global warming trend and whether it recently has stabilized or not. The authors by the way conclude it has not. Their main conclusions however is:

When the AMO is included, in addition to the other explanatory variables such as ENSO, volcano and solar influences commonly included in the multiple linear regression analysis, the recent 50-year and 32-year anthropogenic warming trends are reduced by a factor of at least two. There is no statistical evidence of a recent slow-down of global warming, nor is there evidence of accelerated warming since the mid-20th century.

This study is following the same approach as Foster/Rahmstorf 2011 and Lean/Rind 2008 (trying to correct the global temperature for ENSO, solar and volcanoes) but adds the Atlantic Multidecadal Oscillation to their multiple linear regression analysis. This leads to their figure 1b above. What we see is a longterm trend that has hardly changed during the past century.

Now as always this result can be interpreted in many different ways. The century scale trend is still 0.68 degrees Celsius suggesting little of the total trend of 0.8 degrees C can be attributed to solar, volcanic, ENSO and AMO. That’s what the authors seem to suggest as well when they write (bold mine):

The conclusion that we can draw is that for the past 100 years, the net anthropogenic trend has been steady at approximately 0.08 °C/decade.

So for them anything that’s left after filtering out the natural forcings and natural variability is just ‘anthropogenic’. For me this conclusion is rather premature. But before I explain why let’s focus on the other trend lines that the authors show. Just like Foster/Rahmstorf they conclude that there is no slowdown recently:

There is no statistical evidence of a recent slow-down of global warming

However the trend they find for the recent 32 years (0.07ºC/decade) is far lower than that of Foster/Rahmstorf (0.17ºC/decade). If the approach has any validity at all this would suggest that the AMO alone explains the difference between the Zhou/Tung and Foster/Rahmstorf trend.

The paper by Zhou claims that in the last 32 years, the period in which greenhouse gases are supposed to be the dominant forcings, in fact some 60% (0.1ºC of the total 0.17ºC/decade) of the trend can be ‘explained’ by a combination of ENSO, AMO, solar and volcanic forcing). Ergo, only 40% of the trend could be attributed to other factors among which greenhouse gases are of course a logical candidate.

However there are other candidates as well of course. There is ongoing debate about the influence of siting issues on the temperature measurements on land as well as the Urban Heat Island effect and other socio-economic influences. In a controversial and well known paper Michaels/McKitrick estimated that “Using the regression model to filter the extraneous, nonclimatic effects reduces the estimated 1980–2002 global average temperature trend over land by about half.” If true even less of the remaining trend can be attributed to greenhouse gases.

The Zhou study could therefore have serious implications for our estimates of climate sensitivity. The paper though is completely silent about these potential implications, something that reviewers could have raised.

As said above Zhou and Tung call the remaining century long ‘underlying’ trend ‘anthropogenic’. Whether this is ‘right’ could be questioned with their figure 2 (see below). Here one sees that the anthropogenic forcing (green line) seems to underestimate the adjusted trend in the period (1889-1970) while it seems to overestimate the trend thereafter. This suggests that still not all the relevant factors (either natural or anthropogenic forcings or natural variability) are included in the regression analysis. The residuals in figure 2b still show trends which would not be the case, Zhou and Tung write, if the regression analysis would be perfect.

This leaves enough room for all to bend the paper in one’s preferred direction.

======================================================

Deducing Multi-decadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis

Jiansong Zhou and Ka-Kit TungDepartment of Applied Mathematics, University of Washington, Seattle, WA 98195, USA
Abstract

In order to unmask the anthropogenic global warming trend imbedded in the climate data, multiple linear regression analysis is often employed to filter out short-term fluctuations caused by El Nino-Southern Oscillation (ENSO), volcano aerosols and solar forcing. These fluctuations are unimportant as far as their impact on the deduced multidecadal anthropogenic trends is concerned: ENSO and volcano aerosols have very little multi-decadal trend. Solar variations do have a secular trend, but it is very small and uncertain. What is important, but is left out of all multiple regression analysis of global warming so far, is a long-perioded oscillation called the Atlantic Multi-decadal Oscillation (AMO). When the AMO Index is included as a regressor (i.e. explanatory variable), the deduced multi-decadal anthropogenic global warming trend is so impacted that previously deduced anthropogenic warming rates need to be substantially revised. The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.

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Since the AMO trend (or North Atlantic SST record) for 1910-1945 and 1975-2005 is exactly the same, I do not get from where they got those 40 and 60%.

DirkH

Why do they split the trend at 1970?
A linear trend is a model. If after 1970 a new model is required the only possible reason is the increasing influence of antropogenic greenhouse gases. But then, calling the trend for the previous period an “antropogenic” trend is inexplicable. And all that the added greenhouse gas accumulation would cause is the difference in slope between the two trends, about 0.15 deg C in 40 years or 0.0375 deg C/decade.

ferd berple

The Zhou study could therefore have serious implications for our estimates of climate sensitivity. The paper though is completely silent about these potential implications, something that reviewers could have raised.
==========
The paper is likely silent on purpose. To avoid the firestorm of controversy that would have resulted if they were to questions the orthodoxy. Such an action, to questions scientific beliefs, is to commit scientific heresy. The punishment is to have ones career burned at the stake.

Natural oscillations in the North and the South hemispheres run out of phase. To do a proper job two should be treated separately, and then recombine to observe the global change, but I suggest it would be preferable to present separate graphs first.

Matt Skaggs

This sort of thing reminds me of papers on naturopathy. The herb is first assumed to be therapeutic, the experiment shows an elevated level of some molecule in the bloodstream, and the conclusion of the paper is that the elevated level must cause the therapeutic effect. There is not much difference with saying that the reason our curves don’t overlay perfectly must be AGW.

Anopheles

It starts with HADCRUT4. It doesn’t really matter how much infinitesimal meaning they can squeeze out of that, because they start with HADCRUT4.

This paper appears to make the same blatantly obvious error as Foster and Rahmstorf (2011). It assumes the effects of ENSO can be removed from the instrument temperature record through linear regression. They cannot.
http://bobtisdale.wordpress.com/2012/01/14/revised-post-on-foster-and-rahmstorf-2011/
It also fails to account for the very obvious long-term impact of ENSO on the sea surface temperatures of the North Atlantic. Note how the detrended North Atlantic sea surface temperature anomalies do not cool fully during the La Nina events that follow the El Nino events of 1986/87/88 and 1997/98:
http://i48.tinypic.com/ndldht.jpg

Matt

Boooh! No more research funds for you… 😉 Sorry, I couldn’t resist.

more soylent green!

How did they account for UHI when determining the anthropogentc warming signal? Land use changes from human activity are not properly taken into account.

KR

The AMO is defined as a linearly detrended North Atlantic sea surface temperature (SST). See the AMO index page at http://www.esrl.noaa.gov/psd/data/timeseries/AMO/
Subtract regional temperature (affected by solar, volcanic, ENSO variations) from global temperature (affected by solar, volcanic, ENSO variations), and amazingly enough your signal goes away. The differences are quite small – http://tamino.wordpress.com/2011/01/30/amo/
It will be very interesting to see what their regression coefficients are like – my suspicion is that the AMO will dominate as highly correlated, as changes in the AMO index are driven by those same solar, volcanic, and ENSO effects, and will encompass them.

Matt Skaggs says:
October 17, 2012 at 7:33 am

… the experiment shows an elevated level of some molecule in the bloodstream, and the conclusion of the paper is that the elevated level must cause the therapeutic effect

Pedantic rant:
A molecule is an assemblage of atoms. In this context, for a molecule to be elevated implies a place, e.g. in the head rather than the foot.
An elevated level of some chemical implies a greater number of molecules in one sample versus another.
“Chemical” has been added to the non-politically correct view of the world reserved for horrible pollutants like carbon dioxide. Personally, I like to think I’m full of chemicals, though I confess I have more molecules than chemicals. Chemistry is like that….

Solar, ENSO, AMO and volcanic signals have been removed, dropping the total in half.
The CAGW IPCC narrative says that these other influences are not significant, or less than about 25% (from the leeway I see they give themselves). The paper challenges the assumptions, not the record.
The CAGW enthusiasts would argue that this paper doesn’t change a thing about their stride to reduce fossil fuels. It is the total thermal impact of man and nature that counts. Man can only moderate his part, and with that part moderated or removed, the temperature rise comes to not be “catastrophic”.
So this paper could be used to support the Gore-Hansen-Suzuki screed: take the “known” elements out of his study, and man must be the problem!

According to my findings the AMO (9-10yr) is driven by difference in the phase between solar oscillations and the Earth’s magnetic ripple.
http://www.vukcevic.talktalk.net/EarthNV.htm
A similar process may be driving the ENSO (4.5-5yr) but with near double frequency,
http://www.vukcevic.talktalk.net/ENSO.htm
The AMO is by far more dominant in the N. Hemisphere.
Both oscillations have much longer period component.

Including the AMO as an explanatory variable is a mistake. My own work indicates that global temperature Granger-causes the AMO, not the other way around. Their regression is spurious.

The authors’ conclusion:

The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.

If the residual trend has been remarkably steady for the past 100 years that is proof that it is NOT anthropogenic.
Can’t be sure without access to the full paper, but it sure LOOKS as if they did not include GHGs in their regression analysis:

When the AMO is included, in addition to the other explanatory variables such as ENSO, volcano and solar influences commonly included in the multiple linear regression analysis…

What the hell? That’s not legitimate in the least. Their “regression” does not include the what they are contending is pointed to as the main explanatory variable. As a result, we have no idea from their analysis how much explanatory power GHGs have and how much residual or “unexplained” error there would be.
Crazy. And from the link I see that Forster and Rahmstorf did the same thing. In my field of economics regression analyses are done all the time and I can guarantee that no economist would ever even conceive of the idea of not including their proposed explanatory variable in a regression. That’s the whole point: to get a statistical measure of the explanatory power of the variables one is looking at. Maybe if CO2 data were not available you would try to estimate its explanatory power indirectly by controlling for other variables, but CO2 data IS available.
I think we can be certain that they did run their regression with CO2 included and just aren’t showing us the results. After all, It’s a matter of a few minutes work to pull up a CO2 time series and add it to the regression. Here, I’ll time myself, starting at 10:45AM PDT. Law Dome, 10:46 AM PDT:
http://www.ncdc.noaa.gov/paleo/metadata/noaa-icecore-2455.html
So the authors definitely ran the regression with CO2. They just don’t want to show us how the residual error from their published regression gets divided between unexplained error and an estimate of the explanatory power of CO2, instead pretending that unexplained error IS the estimated explanatory power of CO2.
Can FOIA be used to prove that they did in fact run the regression with CO2? If so, I think this would be a proven case of scientific fraud. These guys are at the University of Washington so maybe it’s doable. But before I go too far with this accusation, maybe post-author Marcel Crok can give us some more detail on what is in the pay-walled paper. Is the impression from the abstract correct? Have they really left GHGs out of their regression? If so, do they offer any rationale?

Kasuha

Yet another regression. An interesting one, but that doesn’t make it right. I don’t think it’s significantly different from many other regressions I have seen so far, including those made to “feed” climate models.
The “anthropogenic forcing” regression is clearly regression to CO2 concentrations, hence the shape. Reduced portion of CO2 influence on climate may be due to last 16 years of warming “stall” because that made the regression to favor natural cycles more than in earlier regressions made for models when this stall wasn’t there.
I don’t wonder they don’t mention implications on climate sensitivity – it would sure make the review process a whole lot more complicated.

Bill Illis

Barton Paul Levenson says:
October 17, 2012 at 10:54 am
Including the AMO as an explanatory variable is a mistake. My own work indicates that global that global temperature Granger-causes the AMO, not the other way around. Their regression is spurious.
—————————-
What causes “global temperature” to go in 50 year up and down cycles then?
You’re right back at north Atlantic ocean cycles then.

Tenuk

Don’t think they include the slow rise in temperature due to recovery from Little Ice Age, or the very long-term effects of the deep Thermohaline ocean currents which could be warmer now following the MWP heating event, May also be other omissions?
The paper is weak as it fails to include all climate drivers and its conclusions are, therefore, less than convincing. I can give this one a ‘C’ at best.

Bill Illis

Here is my own model of Hadcrut4 on a monthly basis (versus annual that this paper uses I assume).
Too close to be a fluke – and my warming rate is only 0.045C per decade on a linear rate (although 2.0*Ln(CO2) provides a closer fit or 1.3C per CO2 doubling)
http://s19.postimage.org/gg5zqvvrn/Hadcrut4_Model_Aug_2012.png

60% are they kidding, it is just about 100%, co2 having 0% effect on the climate, which wil be proven before this decade ends.

this paper is useless more or less, even though it sides against co2 but it is hedging all over the place and doesnot adress why the climate changes and how, which I do ,which will be on my web-site in the very near future.

This paper like almost evey other single paper wants a silver bullet. Now it is the AMO,tomorrow it will be the PDO, then it will be volcanic eruptions, then it will be the thermohalinec circulation.
No concept as usual, that in order to understand the climate one has to take a major comprehensive approach to the subject, this kind of an approach is a waste of time.
I am done.

This is another typically useles IPCC type paper which ab inito assumes “Solar variations do have a secular trend, but it is very small and uncertain.” There is no reason to read any further than that statement. before safely ignoring the rest.

pkatt

“regression analysis is often employed to filter out short-term fluctuations” … It would seem to me that most of our weather and climate are made up of short term fluctuations, to discount them is like putting blinders on. If the volcano didn’t happen, if the Ocean fluctuation didn’t exist. .. Instead of figuring out why they exist science picks and chooses what it wants to include. Blinders with a carrot in front . . . that’s what that is.

These kind of studies make me want to scream. I am really to upset to write anything of significance right now. Of course they believe in AGW, that is why the whole thing is ridiculous. Idiots!

Chris R.

Okay, I must have gotten left behind. I thought that the predicted trend from the GCM models was 0.2 deg. C/decade as of now. The actual warming from approximately 1880 to now–the known record–was about 0.8 deg. C. Now this paper’s residual trend from “just” CO2 is 0.08 deg. C./decade; or just about exactly what we have experienced over the last 130 years?

I’m thinking I must be wrong about them Zhou and Tung failing to regress on CO2. I think their “anthropogenic warming” line must be their C02 regression coefficient times the CO2 time series.

Zhou and Tung ,no nothing about climate, and they show that to be the case in their stupid study.
I am going to do just a very breif outline on what runs the climate to show these fools ,how clueless they are.
Zhou and Tung, here is how it works. It starts with the sun, that is the engine that drives the climate. It is like what gasoline is to a car engine. When the sun undergoes variations in solar irradiance ,solar wind speed or UV light emissions, and geomagnetic activity on the earth,those in turn have an impact on the atmosphere,due to the fact that those solar variations modulate ozone, cosmic rays and visible light ,along with having an impact on gelogical activity, through the ap geomagnetic index. Those in turn effect items such as the atmospheric circulations such as the nao/ao/pna/aao , so2 concentrations,oceanic circulations or phases such as the pdo/amo,and ocean heat content. Those in turn effect items such as enso,arctic sea ice,snow cover ,clouds, precip., which in turn effect the overall albedo of the earth, which utimately effects the temperature.
The reason why temp. have been on a rise since the Dalton Minimum (fools) is because solar activity as measurend by the aa index has been on a dynamic rise throughout that entire period until 2005 unfortunately for you. Since 2005 the sun has gone from a very active phase (1850-2005) to a very quiet phase, which is why the temperature trend has leveled off, and which is why the trend wil be down. The reasons why this is not happening faster are due to ocean heat content lags,which had 150 years of an active sun to gain heat, and the weak max of solar cycle24, both of which will become less of a factor as we move forward through this decade.
The amo,enso and volcanic activity within themselves having nothing at all to do with the temp. rise last century(in the whole big context of things) ,much less co2 which has a negative corrrelation to temperature trends to begin with.
That is , but a very brief rebuttal to your ridiculous study, now that I have calm down some.

S de Prete: co2 having 0% effect on the climate, which wil be proven before this decade ends.
BPL: It doesn’t. Earth is habitable because it has CO2 in its atmosphere. Venus is uninhabitable for the same reason. The difference is the amount.

and geomagnetic activity on earth changes, as a result of solar activity,
Also no should be know. I did this in a slam bang fashion. Sorry .

Alba

Tamino (aka Grant Foster) will have his knickers in a twist over this one.
What? Do the men in the USA wear knickers? But it is interesting to see this phrase being used. For more examples of British phrases which, apparently, are being used in the USA see:
30 of your Britishisms used by Americans
http://www.bbc.co.uk/news/magazine-19929249
Coming in at number 15 is Knickers

richardscourtney

Barton Paul Levenson:
At October 17, 2012 at 3:01 pm you say

Earth is habitable because it has CO2 in its atmosphere. Venus is uninhabitable for the same reason. The difference is the amount.

Well, a bit of that is right.
As you say, Earth is habitable because it has CO2 in its atmosphere.
But at present levels of atmospheric CO2 concentration additional CO2 in the atmosphere has no discernible effect on the Earth’s climate.
And the CO2 in the atmosphere of Venus is not relevant to the climate of Venus which is a net emitter of radiation.
Richard

I meant from this level, where all of the effects of co2 as far as absorbing long wave radiation are at or very close to the saturation point, therefore adding additional co2 (from this level)will have very little further effects, on the temperature.
it is like a sponge soaking water, once it reaches saturation ,it has very little further effect in soaking up more water.

There paper in reality supports the global man made warming hoax, it is not, as it is made out to be.

Louis

“The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.”

What caused AGW 100 years ago? And if the deduced net warming trend has been “steady” for the past 100 years, why are we constantly being told that warming trends, sea levels, and CO2 levels are “accelerating.”

Barton Paul Levenson says:
“BPL: It doesn’t. Earth is habitable because it has CO2 in its atmosphere. Venus is uninhabitable for the same reason. The difference is the amount.”
Yes, the “amount”: because the amount makes the Venusian air so dense you could swim in it (if the heat would wait a bit before burning you up). It is definitely the adiabatic lapse rate due to the “amount” – air pressure, not some property of CO2 specifically.

Will

“It is definitely the adiabatic lapse rate due to the “amount” – air pressure, not some property of CO2 specifically.”
It is fairly easy to demonstrate that the temperature difference between Earth and Venus at the same pressure density is solely accounted for by distance from the Sun, not the composition of the atmospheres.
http://theendofthemystery.blogspot.com.au/2010/11/venus-no-greenhouse-effect.html
A similar calculation can be done comparing the Earth’s temperature of -40C at 70,000m where the atmospheric pressure is the same as the Martian surface. The difference between the -40C and the -64C at the surface of Mars is accounted for by the greater distance of Mars. No other variable is required.

Leo Morgan

Anthony, the ‘snipe’ at Tamino is unworthy of you and your goals.
I’m aware of the history of bad blood between the two of you. I know it’s hard to always be the better man. Especially when it feels like its not being recognised. Yet the civility that you have always insisted upon has contributed to your blog being the most widely read climate blog in the world, and his an also-ran.
I’m no partisan of Tamino’s. You, Anthony, have published my every comment on your blog, whether I agreed or disagreed with the poster. Tamino did not publish my only comment on his site. Amusingly, in the comment he deleted, I was badly mistaken, and he and his supporters could fairly have made much of my error. So I have reason to be pleased he did censor me- but I am affronted by that he did.
Yet as a sincere admirer of yours, I tell you- that line is a mistake.

Brian H

Augggh! A century-long anthropogenic trend? These two authors have just disqualified themselves from any claim to scientific sentience.

“n a controversial and well known paper Michaels/McKitrick estimated that “Using the regression model to filter the extraneous, nonclimatic effects reduces the estimated 1980–2002 global average temperature trend over land by about half.” If true even less of the remaining trend can be attributed to greenhouse gases.”
1. Thats the LAND 30% of the surface.
2. That well known paper has huge data errors. I’ve alerted Ross to them. For example in his regressions he has the population of alaska set as the same as new york city. And has millions of people living in antarctica. Basically he set the population of every grid cell to be the total population of the country divided by the grid cell area. That leads to silly things like french Islands having huge populations and the gobi desert having the same population as Bejing.
I Talked about this on Judiths. Pretty much devastates the paper.
Ross says via mail that he is looking for better data. opps.
next.

KR says:
October 17, 2012 at 10:06 am
my suspicion is that the AMO will dominate as highly correlated, as changes in the AMO index are driven by those same solar, volcanic, and ENSO effects, and will encompass them.

That certainly matches my findings:
http://tallbloke.wordpress.com/2012/10/17/phil-jones-we-dont-know-what-natural-variability-is-doing/

Dr Norman Page says:
October 17, 2012 at 12:22 pm
This is another typically useles IPCC type paper which ab inito assumes “Solar variations do have a secular trend, but it is very small and uncertain.” There is no reason to read any further than that statement. before safely ignoring the rest.

Quite so. If it is uncertain, how do they know it’s small?

Bill Illis says:
October 17, 2012 at 11:41 am
Here is my own model of Hadcrut4 on a monthly basis (versus annual that this paper uses I assume).
Too close to be a fluke – and my warming rate is only 0.045C per decade on a linear rate (although 2.0*Ln(CO2) provides a closer fit or 1.3C per CO2 doubling)
http://s19.postimage.org/gg5zqvvrn/Hadcrut4_Model_Aug_2012.png

Hi Bill,
I’m getting a correlation for monthly data of R^2 =0.873 for my model against HADsst3 from 1876 (start of AMO and SOI data)
http://tallbloke.files.wordpress.com/2012/10/sst-model1.png
No volcanics or SAMO in my model, and the sensitivity is is 1.6*ln(co2)
Solar forcing is bigger in my model, but I can get around the same correlation by changing co2 and solar forcings. You can make anything out of the data within the bounds of uncertainty.
Now that solar is going down as co2 continues to rise, we should find out in a few years time whether solar or co2 is the bigger driver.

kadaka (KD Knoebel)

Wow, inflation has been worse than we thought.
With Mosher complaining about the Michaels/McKitrick paper, in his no-links cryptic fashion where his arguments are somewhere over at Judith’s, I went to go Google the paper.
It was published at the end of 2007, and now he’s suddenly discovered all these flaws?
I found a January 2008 mention, with a link to the abstract “…where nonsubscribers can purchase the PDF for $9.00…”
Now they want $25 for it! A 278% markup in just five years!
I blame Obama.
BTW, Dr. Pielke Sr has the links for the pre-print version, the follow-up, and their data.

P. Solar

figure 2b could be the most informative. After removing their estimate of “anthropogenic” the is a marked down turn after 1970 (just about the same time as the anthro signal becomes significant).
Since all we know about climate has been taken out at this stage , such change in direction either means there was a fundamental change in climate around that time that is being missed or that one or more of the factors that is being removed is/are grossly in error.
That’s the objective over view, now let’s apply Occam’s razor.
This discrepancy starts at about the time the “anthro” signal becomes significant. The deviation of the upward red portion in 2a from the blue trend is about half magnitude of the deviation of the downward red portion in 2b.
Now if we calculate the anthro signal with a climate sensitivity of unity (as would require the physics at the exclusion of hypothetical positive feedbacks that have no observational basis) that up tick would have one third the slope shown in 2a.
The net result would be something very similar to the blue trend continuing undeterred through out the record. In which case, all the sub-century variations have been accounted for.
This paper is probably the clearest indication I have seen so far that demonstrates from global data that the hypothetical GHG _amplification_ is an error.
This paper seems to present strong evidence that climate sensitivity is near unity.

P. Solar

A corollary of the above is that the warming injected by the ENSO signal is cancelling volcanic cooling. I have proposed elsewhere on this blog that ENSO is acting as a negative feedback and correcting the heat loss of volcanic cooling within ten years.
I observed this in the rate of change of OHC, the present paper seems corroborate the idea starting from surface data.
The recovery can be seen in the residual from detecting cyclic variation and removing them
http://i49.tinypic.com/2vjqvpl.png

P. Solar

Alex Rawl says:
>>
Can’t be sure without access to the full paper, but it sure LOOKS as if they did not include GHGs in their regression analysis:
When the AMO is included, in addition to the other explanatory variables such as ENSO, volcano and solar influences commonly included in the multiple linear regression analysis…
What the hell? That’s not legitimate in the least. Their “regression” does not include the what they are contending is pointed to as the main explanatory variable. As a result, we have no idea from their analysis how much explanatory power GHGs have and how much residual or “unexplained” error there would be.
Crazy. And from the link I see that Forster and Rahmstorf did the same thing. In my field of economics regression analyses are done all the time and I can guarantee that no economist would ever even conceive of the idea of not including their proposed explanatory variable in a regression. That’s the whole point: to get a statistical measure of the explanatory power of the variables one is looking at.
>>
That’s a very good point. If they included the anthropological signal in the regression it would probably get weighted by about 1/3, in line with what I pointed out above.

P. Solar

Tenuk says:
October 17, 2012 at 11:36 am
Don’t think they include the slow rise in temperature due to recovery from Little Ice Age, or the very long-term effects of the deep Thermohaline ocean currents which could be warmer now following the MWP heating event, May also be other omissions?
That is very likely what the remaining blue trend in figures 2a and 2b represents. The do not seem to have modelled it explicitly but it is what is left after accounting for all the sub-century variation.

P. Solar

ferd berple says:
October 17, 2012 at 7:11 am
The Zhou study could therefore have serious implications for our estimates of climate sensitivity. The paper though is completely silent about these potential implications, something that reviewers could have raised.
==========
The paper is likely silent on purpose. To avoid the firestorm of controversy that would have resulted if they were to questions the orthodoxy. Such an action, to questions scientific beliefs, is to commit scientific heresy. The punishment is to have ones career burned at the stake.
Yes, I also got the impression they were saying as much as they dared without ensuring the paper got refused. I think there is some important results in there and they did not want t jeopardise the paper by being too clear about what the implications were.
Calling the century scale trend anthropogenic seems more than odd.
“The conclusion that we can draw is that for the past 100 years, the net anthropogenic trend has been steady at approximately 0.08 °C/decade.”
This seems contradictory to labelling the green line which is not constant anthropogenic.
Overall I think the paper could have significant implications for climate sensitivity as it seems to present the blatant deviation caused by current assumptions of amplification in figure 2b.
2a and 2b really invite the reader to notice that there is NO amplification.

Richard: at present levels of atmospheric CO2 concentration additional CO2 in the atmosphere has no discernible effect on the Earth’s climate.
BPL: No. It’s up 40% since the industrial revolution began. It’s the absolute amount that matters, not the concentration. The nitrogen, oxygen and argon that make up more than 99% of Earth’s atmosphere is not radiatively active.
R: And the CO2 in the atmosphere of Venus is not relevant to the climate of Venus which is a net emitter of radiation.
BPL: No, Venus is in thermal balance. You may be thinking of a report a few years ago that Venus radiates 40 times what it receives in the infrared. But that’s not true for the whole electromagnetic spectrum.