Another indication of MWP and LIA being global

Excellent account of the LIA and the superimposed (coincidental?) impact of Icelandic eruptions given by Prof Dawson in “So foul and Fair a Day”.
http://europe.theoildrum.com/node/6387
Some convincing evidence for natural climate cycles comes form Scott Stine’s description of Owen’s Lake (California) being dry 800 years ago. It filled up with water during the LIA, a nice environment for those escaping Hell in Europe to settle.

Also proofs of the same from south america:
http://www.springerlink.com/content/m11m129238u61484/

In the past, critics have said these events to be “regional” implying they occurred only around Europe, due to lack of historical records in other regions of the world.

I read that way of thinking a lot, but It doesn’t make sense under the scientific point of view. If you claim that The MWP and the LIA were regional, you have to prove it, otherwise it shouldn’t be a scientific argument.

@John Egan: I wouldn’t bring plate tectonics into this. It’s a very whacky idea that gained prominence because the older theory couldn’t explain the mechanism. Plate tectonics has changed explanations countless times on its own mechanics and will change again. If you look at the geometry, PT is physically impossible for long distances. In fact, PT fell out of favour with the people responsible for bringing it to prominence. Also, subduction doesn’t exist on other planets. And it doesn’t exist on Earth either even though plenty of “scientists” will try to claim otherwise.

Peer-reviewed to boot!
(Not that it’s important anymore – at least not for the IPCC),
FoxNews covers the IPCC’s F-graded report.
http://www.foxnews.com/scitech/2010/04/19/united-nations-climate-global-warming-ipcc/
Concerning MWP, it was consensus that it existed – until the Hockey-Stick Bros. came around and tried to airbrush it out.
This is yet another arrow through the heart of the bogus AGW tales.

blacks whitewash (12:17:48) :
I think its safe to say anyone who does not have an axe to grind knows that the current warming is not unprecedented.
—-
Indeed. Ever since this all started being about axe-grinding agendas I have relied on this little summary as a guide. Yes, from Nature, but back when it wasn’t compromised by politics, and also in a paper not directly dealing with climate change per se.
I must ask this extremely well informed group commenting here if this still rings true or whether new research has somehow changed this:
“The Greenland (Arctic) and Vostok (Antarctic) ice cores are particularly informative, offering fine temporal resolution and continuity. This has revealed surprising oscillations of climate on a millennial scale within the main 100-kyr cycle. The Greenland Ice Core Project (GRIP) identifies some 24 interstadials through the last ice age with average temperature rising rapidly by ~7 C over just decades. Further ice and sediment cores from around the world are demonstrating the global scale of these major climatic events.”
From: Hewitt, G. 2000. The genetic legacy of the Quarternary ice ages. NATURE, Vol. 405, 22 June 2000 (www.nature.com)
Again: “with average temperature rising rapidly by ~7 C over just decades.”
So did the IPCC gang rebore the ice and find something different?

Woah! Lets not get too excited… these are “proxies” aren’t they?!? Or are there “good proxies” and “bad proxies”???

blacks whitewash (12:17:48) :
I think its safe to say anyone who does not have an axe to grind knows that the current warming is not unprecedented.
Hey there, climategatestuff aka blackwhitewash! Where you been?
Nah, the Mann-made disinformation campaign has run a long time, gone very deep, and is still spreading wide. It’s going to take awhile to get the truth out to the innocently deceived, of which our school systems are currently programming even more as we speak. Then we have the assorted types of the brainwashed to deal with, from the forcefully indoctrinated (“They kept sending me to Save-the-Earth seminars!”) to the willfully-following (“Now I understand why everyone deserves to die.”)
Yup, we got a job ahead of us.

Urederra (12:29:54) :
“… If you claim that The MWP and the LIA were regional, you have to prove it, otherwise it shouldn’t be a scientific argument.”
Actually, this amounts to a classical falsifiable hypothesis. The accumulating evidence of correlated warm episodes in other parts of the world falsifies the regional limitation.

[sarc]
Since this wasn’t reviewed by the relevant people it is irrelevant …
[/sarc]

Are there any climate changes that cannot be explained by a simple cyclical oscillation of all the air circulation systems latitudinally ?

“MrX (12:34:53) :
… I wouldn’t bring plate tectonics into this. It’s a very whacky idea that gained prominence because the older theory couldn’t explain the mechanism. Plate tectonics has changed explanations countless times on its own mechanics and will change again. If you look at the geometry, PT is physically impossible for long distances. …”
PT is at present the only viable model going for large scale geological phenomena. It is the only one that DOES handle the geometry. The geosynclinal theory never did. There are no other explanations that integrate the motions of large scale faults like the San Andreas, volcanic arcs, their geographic correlation with extremely deep trenches, space/depth patterns in seisimicity along continental margins and particularly along subduction zones, triple junctions and a number of other phenomena such as magnetic striping, into one relatively neat mechanical model. Most objections are focused on crustal rigidity and don’t want to accept empirical and laboratory data of plasticity at depth; there’s a propensity to argue that rocks are brittle and can’t really deform. A theory can remain viable as long as it continues to examine itself, which is why the changing ideas about the mechanisms PT are a good thing.

The Medieval Warm Period happened, no if or buts.
To deny the occurrence is to deny reality, geologists and archaeologists have never denied the existence of the MWP.
Some ‘scientists’ who because of it’s inconvenient warming attempted to efface fact from their own fiction. Time and again, more and more confirmation of the MWP comes to light and each fact just simply reinforces the obvious; that the cover up and fudged computer algorithms (Mann) cannot deny the truth and that their flawed hypothesis is further blown out of the water.
Now that is denial for you.

To be moderately nit-picky, I suggest you reorder a couple sentences to:
“Since the Oxygen18 isotope dating method seems well proven –even RC’s Gavin Schmidt likes it– it would seem this study has a good basis for its claims.”
Otherwise Gavin’s “it” is ambiguous, and could be seen to imply his approval of the study (which so far as shown, he hasn’t commented on it) rather than the underlying methodology.

And in related news:
http://www.prnewswire.com/news-releases/climategate-figure-threatens-lawsuit-over-satirical-youtube-video-hide-the-decline—no-cap-and-trade-coalition-says-bring-it-on-91591369.html

The curve is similar to the data from Newton et al (2007) “Indo-Pacific Warm Pool SST Reconstruction (1004 to 1840)”:
http://i34.tinypic.com/2wg7hxy.jpg
Except the Newton curve has a blip in 1463:
http://i35.tinypic.com/11rb3ae.jpg
Those are from my post on SST (paleoclimatological) reconstructions:
http://bobtisdale.blogspot.com/2008/07/sst-reconstructions.html

Stephen Wilde (13:40:39) : You asked, “Are there any climate changes that cannot be explained by a simple cyclical oscillation of all the air circulation systems latitudinally ?”
ENSO, AMO. The apparent 80- to 100-year cycle in the Southern Ocean:
http://i39.tinypic.com/m7wf7t.jpg

MrX (12:34:53) :
“I wouldn’t bring plate tectonics into this. It’s a very whacky idea …”
————
Reply: I agree with Jimmy Haigh’s request for a better theory, MrX. Plate tectonics might be a very whacky (sic) idea, but I’m finding too much evidence to just toss it out unless you’ve got something much more credible than the theory we’re currently using.
Any references? We’re open-minded around here and you won’t get yelled at if what you’ve got is any good.

Bonehead (13:13:20)
There is a huge and compelling literature on the calculation of past sea surface temperatures. This includes thousands of sudies from thousands of marine drill cores and a variety of methods for estimating past water temperatures. The Mg/Ca ratio in planktonic foraminifera shells is one of these methods. It has been cross correlated with several other methods of temperature estimation from foraminifera. It has been checked in the lab by culturing the wee beasties at different temperatures. It has been checked in the field by sampling mordern waters of varying depth, latitude, longitude, temperature, clarity etc. It is also backed by some seriously detailed geochemistry. The effect has been studied extensively in foraminifera. It has also been studied extensively in coral.
The ratio of Mg to Ca in calcite which is secreted during shell production is dependant to a large extent on the temperature of the environment that the organism inhabits. There are some slight variations in the curve for this ratio between different foraminiferal species. This is why the authors of this study concentrated on a single species.
The method has been shown to work in samples from many sites going back hundreds of thousands of years. Now it is being applied with scalpal-like precision to very young sediments. In the future we can expect many more results rather like the those referenced in this article.

“Bonehead (13:13:20) :
Woah! Lets not get too excited… these are “proxies” aren’t they?!? Or are there “good proxies” and “bad proxies”???”

It’s not a question of good and bad proxies it’s a question of cherry-picking. See Briffa and Mann. Even without proxies historical accounts tell us it was global.

MrX “Also, subduction doesn’t exist on other planets. ”
And the sample size is, what, one other planet?
Two?
For what it’s worth, computer modeling indicates that rocky planets somewhat larger than Earth will have subduction, and hence plate techtonics, even without oceans. For Earth, the oceans are necessary, which explains why Venus shows no signs of it. Of course, what we know of Venus’s surface is limited to radar surveys and short lived probes. Another requirement is a molten mantle.
Mars, in its distant and very wet past, before its core cooled off, may have had subduction and plate techtonics, the debate is still open.

Oppo archives her data too. http://www.ncdc.noaa.gov/paleo/pubs/oppo2009/oppo2009.html
Of most importance is the accuracy of the downcore dating. Unfortunately the full-article is behind the Nature paywall so this means a trip to the library.

@Madman (13:03:14) : “Do you think we could get a key or legend describing the different coloured lines in the graph??”
Here is the entire paper. (You need a sub to get the Nature copy, but I found this.)
https://darchive.mblwhoilibrary.org/bitstream/handle/1912/3188/ppnature08233_with_fig%26supple.pdf?sequence=1

PGosselin thanks for that. Every skeptic/doubter/questionaire should keep this link for when told “show us ONE peer reviewed papers”! from the AGW’s:
http://www.populartechnology.net/2009/10/peer-reviewed-papers-supporting.html

The MWP should have never been called into question as there has been suficient properly-validated scientific evidence from disparate parts of the globe of the MWP being a global event around for some years. I have just skim-read studies from five widely-separated sites in New Zealand which all confirm the MWP, but that the MWP was warmer than the current Warming Period.
The arrogance and deception of Mann and the rest of the Hockey Team is staggering in its sheer efrontery.

Ulric Lyons (03:16:29)
Could I ask youto be more specific about the proposed mechanism by which solar variability has it’s proposed effect.
Leif is dismissive of variability in TSI and I tend to accept that.
I have suggested an alternative mechanism which Leif does not accept. Others have suggested ozone related changes in chemical composition and Leif goes with that up to a point.
Can you resolve that aspect ?
I try to square the circle by proposing a much more powerful oceanic influence which sometimes opposes and sometimes suuplements any solar effect. I don’t see how your narrative can fit observations without including another factor such as the oceans except perhaps in the very short term i.e. within the period of a single El Nino or La Nina event. Beyond those timescales the match between solar surface activity and global temperature trends is poor without a variable second force.
Within such short timescales one can get apparent matches between solar surface activity and Earth’s weather (but not really climate) but mostly I see any successes as mere chance combined with rather broad descriptions with a lot of latitude as to scale timing and location. A little like the fortune teller approach in fact.

The wise person, when confronted with evidence to the contrary, admits their mistake. Scientists have no difficulty admitting their mistakes, it goes with the territory, it’s part of the job; $cientists have great difficulty admitting their mistakes for it costs them dearly and they may have to actually start working for a living.
A Scientist is no fool!
A $cientist is a fool!

Stephen Wilde (05:56:13) : Since only recently we have the instruments to “see” all the radiation spectrum, so it is quite hard for the great majority of astronomers and astrophysicists to get rid of what I call the “flintstones´ universe” conception, a paradigm we all were tought as composed of rounded stones (planets) and balls of fire (stars). It takes several generations to change a paradigm. Newton was not so closed minded as he, intuitively, studied the light spectrum, however all what the world inherited from him was the image of an apple falling from a tree, and thus many generations focused on the apple and, as Newton himself, forgot the tree above!

That is a great map, but note in several cases the dates don’t line up as well as you’d need to prove the MWP conclusively. Now, there are two possibilities –one is that it was a rolling regional phenomenon. That one strikes me as pretty unlikely. Or, the other is that the inherent uncertainties in dating the proxies is the problem.

Ulric Lyons (08:09:05) : This is secret!, it has been forbidden by the Holy Inquisition, in other posts, but, anyway you can see it at your own risk:
http://www.vukcevic.talktalk.net/GeoMagField.gif

Has anybody here actually read the paper ?
It’s rather hard to find pre-prints of published papers online:
https://darchive.mblwhoilibrary.org/bitstream/handle/1912/3188/ppnature08233_with_fig%26supple.pdf?sequence=1
Look at the graph at the top of this page:
From the authors’ Figure 2b, adapted below, we calculate that the Medieval Warm Period was about 0.4°C warmer than the Current Warm Period.
What they left out from the paper were the lines representing the 1997-2007 Mean Annual SST (Sea Surface Temperatures) – which are already cooler than current SST’s – and the JAS (July August September) line, which is cooler than the annual mean. This Indonesian site, Makassar Strait, is south of the Equator, so JAS is winter there.
Look at Figure 2a in the paper – the one preceding the modified 2b shown above. The plankton shell data tracks the JAS temperature well from 1850 to 1940, then jumps up to track the Mean Annual Temperature curve.
Huh.
Now, that’s inconvenient.
As the paper says:
Given the evidence that G. ruber tends to record near mean annual SSTs during warm intervals of the last 150 years (Fig. 2a),
and
If, on the other hand, G. ruber calcified preferentially during the JAS upwelling season throughout the study interval,
Those uncooperative little plankton bounced around during the period in which they had both plankton and instrumental temperature data (1850-1980), tracking either the mean annual SST’s, or the coldest ones (JAS). This is a difference of about 0.8 °C.
So, what about the -300 AD to 1980 period ? Any bouncing around there? Certainly. So that whole LIA section in Figure 2b should be shifted up about 0.8 °C, if you want to compare annual mean SST to annual mean SST for the whole graph.
Finally, note that the blue line in Figure 2a (see the paper) ends before 1980.
This is the blue line in the Figure in this thread (above), representing “the Current Warm Period”.
The blue line is from 31MC, the red line is from MD60 – see where they overlap ? The red line is about 0.8 °C higher SST. See Figure 1 for the locations of these two cores – about 50 miles apart, in the Makassar Strait. That makes the entire red line “MWP” temperatures suspect – are they shifted 0.8 °C higher too ?
Now look at global temperatures since 1980 – they are up about 0.6 °C
http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif
If the blue line 31MC SST values were not shifted down 0.8 °C relative to the red line MD60 core values (which should both be measuring the same SST), and the final 30 years of temperature data were added to the blue line, then the current SST would be 1.0 °C warmer than in the MWP.
I guess that’s “within error” as the paper’s authors claimed:
Reconstructed SST was, however, within error of modern values during the Medieval Warm Period from about AD 1000 to AD 1250,
The error bars are pretty large – you don’t know if the plankton are tracking JAS or mean annual SST, and the calculated SST varies by about 0.8 °C for two different cores about 50 miles apart. Clearly they need to look at more cores, and have more “overlapping in time” core comparisons.

@ pgosselin (12:48:09) :
Don’t you mean 701? ; )
700 Peer-Reviewed Papers Supporting Skepticism of “Man-Made” Global Warming