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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Really, this type of mockery ill-becomes you. I guess if you had your way, the first time someone attempted to model physical reality using finite element analysis and failed, they should have just packed it up and gone home, rather than gather data and attempt to refine the model. Current climate models may be wrong, inelegant, and prone to belching in polite company for all I know. The crucial objection is that the current crop of not-ready-for-prime-time computer programs are ill-suited for determining how we intend to spend the public’s money, not that they are a condemnation of models per se.
Is it just me or does their presentation seem less than professional? The conclusions might be wrong too, but the pictures and the like remind me of a term paper.
Theo Goodwin says:
April 11, 2013 at 4:12 pm
…
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I don’t know Theo, I use successive approximation so often that it’s practically my philosophy for living. 🙂 I’ve got to admit that I very rarely get anything complicated right the first time.
D.J. Hawkins says:
April 11, 2013 at 5:11 pm
“Really, this type of mockery ill-becomes you. I guess if you had your way, the first time someone attempted to model physical reality using finite element analysis and failed, they should have just packed it up and gone home, rather than gather data and attempt to refine the model.”
I don’t know about Theo’s view, but as for me my objections are based on my own perception that they seem to spend much less time trying to refine their models to match the data from physical reality than they do trying to “refine ” the data to match their models.
Like it or not, She is in control.
No amount of taxes paid to soothsayers will calm Her tempests.
Maybe, She works in (unpredictable) cycles.
Best to be prepared for Her fits.
Wow! On Tom Nelson’s blog you can find a ClimateGate email exchange between Mann and Phil Jones where they discuss how to manage the problem of the MWP. The exchange took place in 2003, ten years ago, where they talked about enlisting the assistance of staff at the AGU’s EOS publication in helping to “contain” the “putative” MWP. Here: http://tomnelson.blogspot.com/2011/12/mann-would-be-nice-to-try-to-putative.html
Now he is admitting that the MWP existed?
It has been obvious that Mann has been aware of the problems that the MWP and LIA present for the theory of Global Warming for years. Still he presses on because, for some reason, people want to buy what he is selling. How this guy has been able to maintain his job as a scientist, and why people continue to publish what he says completely baffles me. If people simply stopped listening or paying any attention, that would be the end of it.
It is like a medieval belief in witches and spells. The people who attend to this nonsense are as guilty of perpetuating it as the alarmists themselves.
Dave Wendt said:
,“[T]hey seem to spend much less time trying to refine their models to match the data from physical reality than they do trying to “refine ” the data to match their models.”
To which I would add: “And then refine their models to match reality.” Rinse and repeat.
D.J. Hawkins says:
April 11, 2013 at 5:11 pm
Mark Bofill says:
April 11, 2013 at 5:23 pm
I did not have time to make an extended comment. I took for granted that the context is scientific theory. Models are great analytic tools but cannot substitute for scientific theory. Models are wonderful in many contexts and essential for solving many important problems.
However, if you want to argue that models can substitute for scientific theory, I will argue to the death on that one.
There is no point in gearing the models to reproduce reality because it cant be done..
Im sure they have tried and tried again to input the past and every variable under the sun, including the sun to find a pattern.. A constant state of flux and balance in a living organism (our climate) is like trying to model what Im going to do next.. Bathroom, fridge or shopping, maybe another glass of wine.. I dont even know until the urge hit me..
Ever think our climate operates in the moment, for the moment, in spite of the moment..
Effortlessly regulating its needs for no apparent reason.. No rules no roads, just energy transfer because there is so damn much of it there is nothing else for it to do..
How do you model that?
Theo either has a serious issue with Mosher or a bad night’s sleep recently. He mocked what I view as a simple, straightforward presentation of the proper way to go about modelling in general, simply because it came from Mosher. I don’t disagree that there appears to be a great deal of “don’t look at the man behind the curtain” attitude amongst the warmanistas, but let’s try not to match their rigidity, eh?
I’m still hung up on volcano’s..
Our planet and all the life on it, including our climate has been able to handle eruptions big and small.. One medium eruption can put out more CO2 than the entire industrial revolution to date..
How can you come to the conclusion that Mann’s industrial eruption over the last 150 years is any different than any other volcanic eruption? CO2 is simply CO2 isnt it..
Never mind the ash and what it does over the short term.. We are talking about 150 years worth of Mann’s CO2 put into our atmosphere in 18 months..
Again and again..
It makes absolutely no logical sense at all that CO2 drives AGW..
Volcano’s came first with life and our climate coming second.. The fact that we are here is proof positive that our climate can regulate CO2..
AGW is green political nonsense..
Jay says:
“One medium eruption can put out more CO2 than the entire industrial revolution to date..”
And here’s what the USGS says:
“Gas studies at volcanoes worldwide have helped volcanologists tally up a global volcanic CO2 budget…. and studies show that globally, volcanoes on land and under the sea release a total of about 200 million tonnes of CO2 annually. seems like a huge amount of CO2, but…while 200 million tonnes of CO2 is large, the global fossil fuel CO2 emissions for 2003 tipped the scales at 26.8 billion tonnes. Thus, not only does volcanic CO2 not dwarf that of human activity, it actually comprises less than 1 percent of that value.”
Jay, could you explain that monumental discrepancy. Where did you come up with that ‘information’? JP
I have a question for Dr Mann:
If as you say you found external forcings (solar/volcanism) pushed the temperatures down between 1400-1900, in the absence of these external forcings (1900-present) should we not expect temperatures to then bounce straight back up?
It’s like a ball floating in water. Apply force to the ball and it sinks. Remove the force and it rises again back to its natural state.
thesdale says:
“… should we not expect temperatures to then bounce straight back up? It’s like a ball floating in water. Apply force to the ball and it sinks. Remove the force and it rises again back to its natural state.”
Thesdale, the atmosphere is more complex than the water in your analogy. And there are ‘forcingS’, whereas your analogy has only one forcing. The ‘ball’ will come back up, but it doesn’t necessarily “…bounce straight back up… JP
To which I would observe if that were the case the models would converge on reality when in fact they are in parabolic free flight away from reality. You have surely seen the charts that depict this.
John Parsons says:
April 11, 2013 at 8:31 pm
So apply 37 different forcings (that should be enough, eh?), all components resolving to the same vertical temperature force and you’d have “thesdale’s” base case without pontificating needlessly to obfuscate his point. But confusing the issue was your main objective, wasn’t it, John?
Or should I simply state that the overall results are the same whether it’s one or 37 forcings. Once the negative forcings are eliminated, temperature has but one general way to go–and that is up. And since the bottom of the LIA, that’s pretty much what temperature has done (with a few plateaus along the way just to make it interesting). We haven’t seen it go down significantly, which proves “thesdale’s” point.
Mosher writes “You cannot talk about a 10ppm “change” without understanding the fundamentals”
I find that statement slightly ironic when you’ve assumed 3.7W when doubling from 10ppm to 20ppm. Who said the response was linear over such a wide range of doublings? For example would you also expect a 3.7W effect going from 1 to 2ppm? How about 0.001 to 0.002ppm?
lsvalgaard says: April 11, 2013 at 4:35 pm
Yes, because it leads you to ill-founded conclusions. Next question: so what? And indeed, so what that you draw ill-founded conclusions?
………….
ill-founded conclusions?
Nonsense, more likely it doesn’t suit your science presentation politics.
DD More says:
April 11, 2013 at 11:28 am
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Further to your comment.
Despite claims to the effect that CO2 is a well mixed gas, CO2 is not particularly well mixed and its concentration varies quite substantially between seasons, and even the time of day.
The experiments to which you refer (performed in the 1800s and early 1900s) appear to have been conducted to a high standard with fairly accurate equipment. These experiments appear to have been dismissed without (in my opinion) a well and sound reasoned explanation. If their findings were valid, it would destroy the CO2 induced warming conjecture (this may be the motive behind their dismissal).
I am of the view that those experiments should be replicated today. The same sites should be sampled, at the same time of year (and time) and the results analysed using the same equipment and methodology.
If these experiments were replicated, we would have a much better appreciation of the comparison of today’s levels of CO2 with past levels of CO2 in the 1800s and early 1900s. This would be useful and valuable.
TimTheToolMan says:
April 11, 2013 at 11:36 pm
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Sensitivity to CO2 (if Earth’s climate is at all sensitive to that gas) must have varied greatly over time, and over concentration levels otherwise the oceans would not have formed or would have boiled away, long ago. The earth would be like Venus (not necessarily for the same reasons).
How many doublings of CO2 have there been over the entire history of our planet?
It appears that the earliest atmosphere was hydrogen and helium, and it was only through later volcanic activity that CO2 was spewed into the atmosphere. During the first eruptions, CO2 must have been a minimal component in the atmosphere. So logic suggests that there must be literally hundreds of doublings.
fobdangerclose says:
April 11, 2013 at 12:46 pm
Oh that this pin head were larger,
Danceaway, Danceaway, Danceaway all,
On prancer Mann, On fancy Gore,
Danceaway danceaway, all
Smaller feet, smaller reduced to
Danceing small, all,, feet intangled
Smile, Dance, show all, you can still
Dance the hockey stick dance for all,
Gold, fools gold, mine for all time,
This CO2 fraud miss-minted rusty coin.
Oh, that this pin head would just stop
srinking, shrinking no room for all.
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Very GOOD! Smiling as I write. Conjures the image beautifully.
D.J.Hawkins, I agree that Mosher gave a pretty tepid view of what modeling should be about. However, I think the problem is, that is not what we have been seeing from the modeling community. What we have seen is blatant apptempts to support “The CAUSE”. In real science we should see competing methodologies from the various modeling camps. Instead, we see a rigid approach where GHGs are the only possible driver of climate change. I think that is what drove Theo’s disdain for Mosher’s comment. Mosher’s comment ignored reality. Dave Wendt hit the nail on the head.
fobdangerclose says:
April 11, 2013 at 12:46 pm
You’ve stuck this picture in my head! If this was the late 19th century I’d expect to see a tin kids game with all this prancing and precarious balance! How about an Ap? The Climate Science Ap? Updated as they fall off?
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richard verney says:
April 12, 2013 at 3:23 am
Despite claims to the effect that CO2 is a well mixed gas, CO2 is not particularly well mixed and its concentration varies quite substantially between seasons, and even the time of day.
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Richard, the GHG effect of CO2 is only important at high altitudes (say, above 30000 ft). Ground CO2 has little GHG effect.
Theo Goodwin says:
April 11, 2013 at 6:07 pm
However, if you want to argue that models can substitute for scientific theory, I will argue to the death on that one.
————
No, I’m only addressing this because I don’t want you walking away thinking that’s my position. All I was saying is, I don’t see anything unreasonable about refining a model by comparing it to reality, looking for systemic shortcomings, and correcting them. It’s not like they’re going to be able to ‘black box’ it, by fiddling with knobs until they get it empirically correct without understanding what’s really going on. You can make it match the past that way but you’ll never get it to predict the future at all doing that. Maybe we will never get it right; maybe we don’t understand enough of what’s going on. Still, looking at where why and how the models fail to match reality can provide valuable insight into what we don’t know about the system.
People who make claims based on climate models irritate me as much as they irritate you, just so you know. 🙂