Ice core data shows CO2 levels changed less than 10 parts per million from 1600-1800 during the MWP.
From the Hockey Schtick: A new paper from Schurer et al (with Mann as co-author) finds that climate “models cannot explain the warm conditions around 1000 [years before the present, during the Medieval Warming Period] seen in some [temperature] reconstructions.”
According to Schurer et al, “We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900.” They also claim, “but for the first time we are also able to detect a significant contribution from greenhouse gas variations to the cold conditions during 1600-1800.” This claim is highly unlikely given that ice cores show CO2 levels only changed by less than 10 ppm from 1600-1800, and the effect of 10 ppm CO2 on the climate today remains undetectable even with modern instrumentation.
Separating forced from chaotic climate variability over the past millennium
Andrew Schurer,1 Gabriele Hegerl,1 Michael E. Mann,2 Simon F. B. Tett,1 and Steven J. Phipps3
Journal of Climate 2013 doi: http://dx.doi.org/10.1175/JCLI-D-12-00826.1
Abstract
Reconstructions of past climate show notable temperature variability over the past millennium, with relatively warm conditions during the ‘Medieval Climate Anomaly’ (MCA) and a relatively cold ‘Little Ice Age’ (LIA). We use multi-model simulations of the past millennium together with a wide range of reconstructions of Northern Hemispheric mean annual temperature to separate climate variability from 850 to 1950CE into components attributable to external forcing and internal climate variability. We find that external forcing contributed significantly to long-term temperature variations irrespective of the proxy reconstruction, particularly from 1400 onwards. Over the MCA alone, however, the effect of forcing is only detectable in about half of the reconstructions considered, and the response to forcing in the models cannot explain the warm conditions around 1000 [years before the present] seen in some reconstructions. We use the residual from the detection analysis to estimate internal variability independent from climate modelling and find that the recent observed 50-year and 100-year hemispheric temperature trends are substantially larger than any of the internally-generated trends even using the large residuals over the MCA. We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900, but for the first time we are also able to detect a significant contribution from greenhouse gas variations to the cold conditions during 1600-1800. The proxy reconstructions tend to show a smaller forced response than is simulated by the models. We show that this discrepancy is likely to be, at least partly, associated with the difference in the response to large volcanic eruptions between reconstructions and model simulations.
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Heck, the climate models can’t even explain the present, let alone the past, so this really isn’t a surprise:
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So he admits that there IS a medieval warming period – what does that say about his hockey stick which denies it existed?
“We show that this discrepancy is likely to be, at least partly, associated with the difference in the response to large volcanic eruptions between reconstructions and model simulations.”
Looking at the 1000 year climate simulations and focusing on the 1750 to present time segment,
we can also see a discrepancy between observations( Berkeley Earth) and the model results.
The discrepancy is systematic: models tend to overestimate the cooling response to volcanos and tend to predict a faster “rebound” than observations show. This would point to two areas that models need improvements in. go figure. you build a model. you run it. you find the systematic issues. you fix them.
Is Mann saying that the hockey stick for the last thousand years was shaped like a U?
Mark W… right on: the Medieval Warm Period is gone so only the Medieval Climate Anomaly exists now!
Isn’t that funny that everything is an “anomaly” supposedly deviating from a “normal” climate… that is stable? This reminds us of the “perturbations” supposed in meteorology to disturb a field that was normal, fine, healthy, clean, loving, happy and most importantly stable. This vision is so obsolete but very useful for the IPCC and other Mann and warm mongers.
Steven Mosher:
Your post at April 11, 2013 at 1:50 pm says
Looking at the 1000 year climate simulations and focusing on the 1750 to present time segment,
we can also see a discrepancy between observations( Berkeley Earth) and the model results.
The discrepancy is systematic: models tend to overestimate the cooling response to volcanos and tend to predict a faster “rebound” than observations show. This would point to two areas that models need improvements in. go figure. you build a model. you run it. you find the systematic issues. you fix them..
No, I will NOT build the climate model you suggest because I don’t understand climate sufficiently well to build one that will reveal systematic errors that can be corrected.
Of course, I am not alone in this ignorance of climate. Everybody has it.
NOBODY UNDERSTANDS CLIMATE SUFFICIENTLY TO BUILD A CLIMATE MODEL AND TO DO AS YOU SUGGEST.
The problem is that the existing climate models have been built by people who pretend they do not share this ignorance of climate. They do.
Richard
“This claim is highly unlikely given that ice cores show CO2 levels only changed by less than 10 ppm from 1600-1800, and the effect of 10 ppm CO2 on the climate today remains undetectable even with modern instrumentation.”
You cannot talk about a 10ppm “change” without understanding the fundamentals
A change from 10 to 20 is about 3.7 watts
A change from 170 to 180 is about .3 Watts
A change from 275 to 285 is about .2 Watts.
A change from 380 to 390 is about .13 watts
Steven Mosher says:
April 11, 2013 at 2:08 pm
But what’s not stated, is this difference is in the dry air temperature of the clear sky to space.
On a 35F day that temp was measured with an IR thermometer as -40F, with e at 0.95 that is 159.17 watts/sq M, verses the 50 degree asphalt at 346 watts/sq M, you’re 0.13 watts is -39.91F, 0.09 degrees warmer.
I measured a 9 degree drop in temps in 11 hours on a clear night, some 4.62-4.88 million joules/sq meter.
Bill Illis, thanks for the link. It does show how they rigged the whole thing, not dissimilar to Marcott in order to show that the last 50 years are “unprecedented”: chose proxy reconstrutions that artifically smooth the past, adjust the models to replicates that stuff, pretend the slight differences can be explained by natural causes and then graft the HADcruT. Elementary my dear Watson!
Assuming that MWP was a N. Hemisphere initiated event it could be reproduced from other natural climate independent events.
It is variability in the Arctic Ocean’s currents that is the cause of the most of the climate’s natural variability. Extent of the cold Arctic waters outflow in turn regulates the inflow of Atlantic water warming the Arctic Ocean and consequently regulating the Arctic temperature, which is the main contributor to warming and the initiator of cooling.
Crucial to this warm-to-cold oceanographic choreography is the Denmark Strait
Denmark Strait is a bottleneck in a ‘superhighway’ in the oceans’ global circulation . The Arctic overflow water (about 3 Sv), the largest of the deep, overflow plumes that feed the lower limb of the conveyor belt and return the dense water south through gaps in the Greenland-Scotland Ridge.(WHOI)
In this link
http://www.vukcevic.talktalk.net/Arctic-NV.htm
I reproduce temperature changes since 1660, to compare with the CET available data
– first illustration shows The North Icelandic Jet current -NIJ. At its source the ocean heat loss to atmosphere is generator of the Icelandic Low atmospheric pressure system, determining latitude of the polar jet stream over the North Atlantic.
The NIJ is a cold current that runs between Greenland and Iceland at a depth of about 600 meters at sea bottom, across the Icelandic plateau.
The NIJ contributes to a key component of the Atlantic Meridional Overturning Circulation- AMOC.
– second illustration shows the Denmark Strait’s bathymetry and its critical properties for the passage of the NIJ further south, as the main variable contributory component to the subpolar gyre, the home of the AMO.
– third illustration shows correlation of the geological records in the area to the past solar activity (for time being an impenetrable geophysical quandary), but it does explain why many credit the sun for the climate’s natural variability.
– forth illustration shows historic correlation between geological records, the CET and the trailing North Atlantic SST
– fifth illustration shows the above in more detail.
– sixth illustration shows change in the local magnetic field (proxy to the geological movements) and its correlation to the global temperature reconstruction.
TomRude says:
April 11, 2013 at 1:57 pm
Mark W… right on: the Medieval Warm Period is gone so only the Medieval Climate Anomaly exists now!
Isn’t that funny that everything is an “anomaly” supposedly deviating from a “normal” climate… that is stable?
============================================================
It’s an abuse of language,.
Capital offence in my book. A certain Mr. Orwell had much to say about this.
No doubt we will soon be told that the other Holocene Warm Periods were also anomalous. Indeed, it will be that any warmth that is not directly CO2 generated will be anomalous.
Mann truly is a clown.
@ur momisugly somebody says:
April 11, 2013 at 12:01 pm
“Ice core data shows CO2 levels changed less than 10 parts per million from 1600-1800 during the MWP.”
I think you meant LIA.
Garethman, yes, I noticed that, very confusing, is this poor processing or have I missed something?
poooooooottototottitieirghuerhg says:
April 11, 2013 at 12:05 pm
Earth to Leif Svalgaard, comments?
“We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900″
The effect of the solar driver [green line] in last slide of http://home.badc.rl.ac.uk/mjuckes/meetings/reading2012/pdf/schurer_variability.pdf
is negligible [less than 0.1 degrees]. That leaves the real and large effect from volcanoes.
Steven Mosher says:
April 11, 2013 at 2:08 pm
“You cannot talk about a 10ppm “change” without understanding the fundamentals
A change from 10 to 20 is about 3.7 watts.”
In some laboratory. Probably an imaginary one. No such calculation has ever been made in the earth’s atmosphere. Your contempt for empiricism is turning into fantasy.
“Michael Mann says climate models prove Kennedy was shot by the CIA from the grassy knoll, also show moon landing was faked….”
Uhh, right Michael. Perhaps you should tell your fan Stephan Lewandowsky about this.
vukcevic says:
April 11, 2013 at 2:22 pm
– third illustration shows correlation of the geological records in the area to the past solar activity (for time being an impenetrable geophysical quandary),
Not at all, just a spurious correlation without any physical basis
Its politically acceptable to acknowledge a Little Ice Age, but not a Medieval Warm Period. Therefore by fiat, it becomes the ‘Medieval Climate Anomaly’ (MCA).
What will they call it when the current “interglacial period” descends into the the next glaciation? The low density water period? (LDW)?
‘Oh! If the computer models can’t really explain it, then we will have to fabricate the gaps.’ So it becomes false!! Simple!
Anthony,
I’m not sure why you would show a graph of methane (CH4) concentrations as this is input to the models and not an output (prediction). Perhaps you meant to show the temperature graph from this link.
http://wattsupwiththat.com/2012/12/14/the-real-ipcc-ar5-draft-bombshell-plus-a-poll/
REPLY: Thanks, my mistake, I grabbed the wrong graph for cut/past, fixed now. – Anthony
davidgmills says:
April 11, 2013 at 1:53 pm
Is Mann saying that the hockey stick for the last thousand years was shaped like a U?
———————————–
Yes, it’s now a warped hokeystick.
cn
lsvalgaard says: April 11, 2013 at 3:00 pm
vukcevic says:April 11, 2013 at 2:22 pm
– third illustration shows correlation of the geological records in the area to the past solar activity (for time being an impenetrable geophysical quandary),
…………..
Not at all, just a spurious correlation without any physical basis
You may call it spurious because either you don’t understand reasons for it (I do not) or it doesn’t suit your science presentation politics (which is your own business), either way it is of no consequence to the correlation’s existence.
Does it matter?
It does if true, sunspot as such appears do not have required power to move ocean’s temperature, tectonics does via effect on the ocean currents.
Shown is the period (1880-2012) where there are good data
http://www.vukcevic.talktalk.net/SSN+NAP.htm
Steven Mosher says:
April 11, 2013 at 1:50 pm
Looking at the 1000 year climate simulations and focusing on the 1750 to present time segment,
we can also see a discrepancy between observations( Berkeley Earth) and the model results.
The discrepancy is systematic: models tend to overestimate the cooling response to volcanos and tend to predict a faster “rebound” than observations show. This would point to two areas that models need improvements in. go figure. you build a model. you run it. you find the systematic issues. you fix them.
This discrepancy is well known. However, ‘fixing’ it requires the CO2 sensitivity to be reduced, which is why it hasn’t been fixed to my knowledge. Although in the, anything is possible, wonderful world of climate science, they may have reduced the CO2 sensitivity in the models and not told anyone, as it’s really not that important.
Steven Mosher says:
April 11, 2013 at 1:50 pm
“Looking at the 1000 year climate simulations and focusing on the 1750 to present time segment,
we can also see a discrepancy between observations( Berkeley Earth) and the model results.
The discrepancy is systematic: models tend to overestimate the cooling response to volcanos and tend to predict a faster “rebound” than observations show. This would point to two areas that models need improvements in. go figure. you build a model. you run it. you find the systematic issues. you fix them.”
Mosher’s New Model-Specific Scientific Method. Here it is:
1 Construct your model.
2 Run and get results.
3 Check the results against reality.
4 If the model failed to predict reality, it is falsified. NO, NO, NO, says Mosher.
In the New Model-Specific Scientific Method, you change the model. Wow. Amazing. Just add some ad hoc hypothesis and you are on your way. No more old fuddy duddy falsification.
Mosher, The Galileo of Climate Science.
“We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900, but for the first time we are also able to detect a significant contribution from greenhouse gas variations to the cold conditions during 1600-1800. ”
Aren’t these the same bunch of geniuses who have been giving anyone who has even suggested the Sun might play a role in driving the climate the big horse laugh? And how exactly does “explosive volcanism” drive the climate to something like the MCO? It has been my impression that “explosive volcanism” is considered to be a significant driver of global cooling, not warming.
I am once more, for more times now than I can even approximate, struck by the towering irony that any Hollywood celebutard, MSM human press release fax machine, or brain dead politician in the world feels free to step in front of any available microphone, camera or keyboard and boldly declare that anyone like myself, who is not willing to be an epistemological mattressback for all of this hyperbolic climate catastrophism, must be some kind of a congenital moron.
From the beginning of my attempts to understand this topic I have always been seriously underwhelmed by the quality level of the science that has generated this controversy and frankly that view extends to all sides. I have found myself firmly in the “skeptical” camp for several fairly simple reasons
!) From my study of the philosophy of science, skepticism seems to be the primary and ultimate duty of anyone who seeks to “know” anything about the world and universe we inhabit. Personally I tend toward the view that science, even when done with ultimate rigor and integrity, can only allow us to have slightly stronger suspicions that what has been presented is the best available guess at the moment and that providing actual “knowledge” is beyond its logical capabilities.
2) The people who inhabit the skeptical side of this controversy seem to do their work with much more of the humility that 1) above suggests to me is the second leading requirement to be a true scientist. They exhibit much less of a tendency to declare that the work they have done definitively “demonstrates” or “proves” anything and generally seem to operate in a manor that cleves much closer to what I think of as the scientific method i.e. openness about methodologies and data including inconvenient or countervailing data which might weaken their argument.
3)Though I list this third, if I am truly honest with myself, it is probably my number one concern. It is that no one from the skeptical side suggests that their work demands that the world transform itself in ways that are profoundly detrimental to personal liberty, human prosperity, human wellbeing, and in fact the wellbeing of almost all of life on the planet. The “believers” on the other hand act as if the dogmatic certitude of their ends justifies absolutely any means necessary to enforce them on the rest of us. In a sense they are quite correct in their belief that AGW will necessarily turn into CAGW, but they seem incapable of seeing that the real catastrophes have occurred and will continue to occur because of the hugely damaging and ultimately ineffectual remedies for which they demand docile acquiescence from the rest of us. Biofuels, windfarms, carbon taxes and credits and the whole plethora of supposed AGW cures foisted on the world have already inflicted much more damage on human prospects and the global environment than any but the most hyperbolic of AGW catastrophe scenarios have any possibility of matching.
4) I will add this one even though it will tend to undercut my presentation of myself as an objective observer. In all my time as a denizen of this and other related sites I have never had the pleasure of meeting any of the contributors or commenters whose views on this topic seem anywhere close to my own, but I have always felt that there were a great number I could envision spending a pleasant day or evening with, gathered around a table somewhere, sharing appropriate beverages and perhaps some good cigars and conversing about the climate or any other topic that might arise. Though my personal familiarity with the purveyors of climate dogmatism is no greater than for the folks here, almost none of them have engendered a similar sympathetic response. In fact, I would hesitate to be in the same room with most of them because of a very real fear that I would be faced with a commanding Ben Santer-like compulsion to push a fist through their faces. I haven’t actually struck anyone in anger since I was in the second grade, so I could probably restrain myself, but the prospect of having any fun around these dolts is so slim that it”s not worth the chance that I might not. In the end, even if they should somehow miraculously convince me of the correctness of their position, I would still have a difficult time aligning myself with them, because they almost all strike me as a bunch of j**koffs!
vukcevic says:
April 11, 2013 at 3:52 pm
Does it matter?
Yes, because it leads you to ill-founded conclusions. Next question: so what? And indeed, so what that you draw ill-founded conclusions? That matters because it dilutes the science-content of WUWT.
But how can they when