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.
================================================================
Heck, the climate models can’t even explain the present, let alone the past, so this really isn’t a surprise:
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Reality doesn’t conform to the models, there fore reality must be wrong.
/sarc
He is quick to avoid leaving anything stupid unsaid. Models only report back what we tell them and in a way we have told them. If climate models were self-modifying AI they would surely pull the pin before dishing out the trash they are told to create.
Off topic – is Anthony aware of this? Behind the scenes shenanigans about the BBC and 28Gate
http://www.thegwpf.org/28gate-climate-bias-future-bbc/
erhhm
Odd. First post to be moderated, second with URL not.
How does that work? Not what I would expect – the other way round I would,
MattS, That is no need for the /sarc, tag, as sadly, the alarmist warmists actually appear to believe that. They have more trust in the models, (which have had to be constantly re-engineered to retrospectively “predict” the past temperatures that they failed to predict in reality), than trust the actual real historical data. They will not believe the data until it has been adjusted to match the models.
And they have the bare faced cheek to call themselves scientists?
I DEFINITELY believe that you are correct Anthony.
Conclusions – Nothing.
Sorry – what MWP?
Reblogged this on Signaleer and commented:
New climate change article from WUWT.
“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.”
They find – as ever – just what they want to find.
Wait, I thought Mann had proved conclusively that neither the Medeval Warm Period or the Little Ice Age had ever happened.
I’m getting confused again.
I wonder:
Do climate models explain Michael Mann?
Nothing new,
Already demonstrated many times.
for example in
Scafetta N., 2010. I cambiamenti climatici sono regolati da cicli naturali di origine astronomica (Climate change is regulated by natural cycles with an astronomical orogins). Il 21mo Secolo, Scienza e Tecnologia 1, 5-10 (2010). (figure 6)
http://people.duke.edu/~ns2002/pdf/21mo-secolo.pdf
and about the 20th century, look at
Scafetta N., 2012. Testing an astronomically based decadal-scale empirical harmonic climate model versus the IPCC (2007) general circulation climate models. Journal of Atmospheric and Solar-Terrestrial Physics 80, 124-137.
http://www.sciencedirect.com/science/article/pii/S1364682611003385
For those who may be interested, I am keeping a comparison between the forecast made with my proposed astronomical based model of climate variation vs. the IPCC GCMs projection at my web-site where my proposed model clearly outperforms until now the IPCC GCMs.
http://people.duke.edu/~ns2002/#astronomical_model_1
Michael Mann says climate models cannot explain the Medieval Warming Period – I say they can’t even explain the present
Yeah, but…
You say it on a board read by thousands,
while he says it where many less will read it but the main stream media will quote it as gospel everywhere.
It’s the first time i see Michael Mann participating on proving GCMs wrong.
…A new paper from Schurer et al (with Mann as co-author) finds that climate “models cannot explain the warm conditions around 1000 …
Umm.. therefore the MWP didn’t exist?
Isn’t that how climate science works? ” I can’t see any other reason for what happened apart from the one I believe, so that MUST be the right one…”
Ken Hall,
The /sarc tag was there so people wouldn’t think I believe that.
Dr. Nicola Scafetta,
It would be interesting to have an ongoing chart of the -residuals- of all of the competing models. Or, at least, the running least-squared error between models and obvservations. Both as independent models and as the “ensemble”.
This is a pretty stock method of comparing models with reality, I know of no legitimate reason to avoid this for climate science.
To be blunt Mr Mann needs to learn the difference between his ares to his elbow. Before Mr Mann perpetrated the Hockeystick fraud, he first claimed MWP which did not was so insignificant it did not merit as much as a pimple bump on an elephants arse. Then he claimed it existed but only in northern Europe, therefore it wasn’t representative or have any effect on global temperatures. Mr Mann your wrong as usual 1-The MWP was warmer for a longer period than any present day warming. 2- there is a mountain of evidence it was worldwide in extent. Mr Mann how can we believe any thing you say, your track record is questionable at best and outright fraud at worst!
Presentation from Schurer on the paper.
http://home.badc.rl.ac.uk/mjuckes/meetings/reading2012/pdf/schurer_variability.pdf
DaveG says:
Correction:
To be blunt Mr Mann needs to learn the difference between his ares to his elbow. Before Mr Mann perpetrated the Hockeystick fraud, he first claimed the MWP was insignificant that it did not merit as much as a pimple bump on an elephants arse. Then he claimed it existed but only in northern Europe, therefore it wasn’t representative or have any effect on global temperatures. Mr Mann your wrong as usual 1-The MWP was warmer for a longer period than any present day warming. 2- there is a mountain of evidence it was worldwide in extent. Mr Mann how can we believe any thing you say, your track record is questionable at best and outright fraud at worst!
Using plant stomata however the ice core levels may not be the best measure of CO2 levels.
Studies of plant stomata show that the currently-held view of predominantly stable CO2 levels (260-280 ppm) before the Industrial Revolution (1750 AD, i.e. 200 years B.P.) may be an inaccurate view. CO2 levels appear to have regularly exceeded 280 ppm– the average of CO2 concentrations across the Holocene interglacial period (last 11,000 years) appears to have been approximately 305 ppm.
and
In the 1800’s direct air CO2 measurements were performed by various researchers. Interestingly, the CO2 levels reported by them were mostly in excess of 300 ppm. For reasons that are unclear, only a few of these tests were considered valid by G.S. Calendar (1898-1964)– the grandfather of the theory of man-made global warming. Today, the remaining data are largely ignored,
http://www.geocraft.com/WVFossils/stomata.html
Still do not understand how the magical CO2 decides how and when to affect the air temps.
“We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900.”
… but now the lack of explosive volcanism and variations in solar output (solar maximum) is not the main drivers of 1900-today’s much better climate ?? … as if as if we were never suppose to rebound from that icy period in history ??
Lopsided climate “science” is all they feed to us today. It is nothing but crap and should be called what it is.