Dec 11 2011

Hiding The Medieval Warm Period

Not surprisingly there is so much more damning information in the 5,000+ new Climategate emails it is hard to know how to present it. You could do large posts noting all the incidents of unscientific behavior, or you could do tons of small ones on each instance. I have a larger post in mind that juxtaposes the IPCC claims against the behind the scenes discussion by authors (which show an enormous gap between the science and the claims).

But today, being a day for decorating the tree, I will focus on one email and how it contains  evidence of covering up or filtering out contrary scientific results that would undermine the IPCC claims that our current climate is unprecedented.

The email is #0475 and is from Mar 2002. It is between Ray Bradley and Ketih Briffa as they work on an IPCC report. Ray responds to comments by Briffa to make changes the report. The changes seem reasonable until the last topic:

I cut Hammer ref
I just thanked “ll those who provided data”
I was looking at Graybill & Shiyatov Fig 20.6, but you are right that the  warmest period was after 1160….though some argue the MWP extends into the  14th century….certainly it shows a cold 11th century.  So I’lll cut that  reference, as requested…

I conclude Briffa had suggested swapping out studies by Fischer and Springer Verlag over the Graybill & Shiyatov work in Russia:

>for the melt record (l) use .
>2. “Intercomparison of….techniques”, Fisher and others.1996. Nato
>ASI Vol 141, “Climate variations and forcingmechanisms of the last
>2000 yrs”, Springer Verlag etc. pp 297-328.
>Can not track down yet where the low re one came from (can you ask Dave
>Other points are ok
>Did you track down the Hammer ref (some European conference) ?
>Do you need list of acknowledgements yet? Should include
>Mike Salmon for drawing the figure
>and Fisher, Black, Luterbacher, presumably Johnsson ,Bianchi,Kegwin,
>van Engelen,Keith Barber and Darrel.Maddy, for the data I used.
>I am really pushed , sorry about brief reponse- honest.

As with most short emails and limited context it is difficult to be sure, but it seems Briffa was concerned about Graybill & Shiyatov because this tree ring study blows a lot of holes in the Hockey Team’s claims about the  supposedly geographically limited nature of the Medieval Warm Period (the Hockey Team’s latest unproven excuse to claim the ‘globe’ was not warmer than today). Ray originally tries to include the study since it is both valid and applicable:

>At 10:46 PM 3/4/02 -0500, you wrote:
>>yes–they do show a MWp in shiyatov and graybill 1992–but i added briffa
>>2000, too.
>>i still need a response to my last email

Ray Bradley included Graybill & Shiyatov, and later Briffa requested he pull it -  the reason clearly being concern over the MWP (Medieval Warming Period).

So, what does that study say? The study is one of a series discussing the high altitude tree line response to climate in Russia. In this independent study siting Graybill and Shiyatov (on which Ray Bradley is co-author – “Climatic change at high elevation sites“, Diaz, Beniston & Bradley) we learn this:

Beyond the realm of snow and ice, and alpine tundra, the tree-line defines an important climate-related ecotone. Although the tree-line itself varies in structure and composition from one mountain region to another, and is subject to many potentially limiting ecological constraints (Tranquillini 1993) climate is the dominant control, at least away from the oceanic margin. Consequently evidence of past changes in tree-line position is generally interpreted in terms of variations in summer temperature.

OK, this discussion indicates high altitude tree line locations are a strong indicator of past climate. Probably orders of magnitude better than tree rings – where non-temperature ecosystem factors,  in tandem with the genetics of the species and individual trees, overwhelm any temperature signal. The tree-line is a feature of the complete population of local trees and has much less influence from the same factors that make tree rings lousy measures of past local climate (let alone past regional, hemispheric or global climate).

If I was weighting proxies I would weight tree line data orders of magnitude over tree rings. So what’s the MWP issue here? It’s pretty stunning:

Radiocarbon-dated microfossils (tree stumps or wood fragments) from above the current tree-line can thus provide dramatic testimony of warmer conditions in the past.

Holy Hockey Puck Batman! There is ‘dramatic testimony‘ of warmer past conditions in Russia!

But wait, there’s more:

This is well-illustrated in the Northern Urals where now dead trees beyond the tree-line have been dendrochronologically dated to obtain information on the timing of past tree growth at high elevations (Shiyatov 1993). This reveals that most of the trees were growing in the 10th-12th century A.D.; no trees where found to date from the late 18th and 19th centuries, indicating the tree-line had retreated at that time. This evidence is strongly supported by tree-ring studies in nearby forests, where maximum ring widths where found at the time the forest advanced and minimum ring widths where characteristic of the 18th-19th centuries (Graybill and Shiyatov, 1992).

The science literature for this conclusion is pretty clear - it was MUCH warmer in the Medieval Period than today:

The location of the treeline is largely controlled by summer temperatures and growing season length. Temperatures have responded strongly to twentieth-century global warming and will display a magnified response to future warming. Dendroecological studies indicate enhanced conifer recruitment during the twentieth century. However, conifers have not yet recolonized many areas where trees were present during the Medieval Warm period (ca AD 800–1300) or the Holocene Thermal Maximum (HTM; ca 10 000–3000 years ago).

The tree-line has responded to the end of the Little Ice Age (as one would expect), but we have yet to reach the same line that existed in prior, non-industrial times. So today’s climate is not warmer than the MWP. End of story. Tree rings have no argument to disprove the tree-line.

Which is why Graybill and Shiyatov 1992 had do be removed from the IPCC report. It would not just undermine the Hockey Stick. It would be stronger evidence than the tree rings that today is not as warm as the MWP. It is hard to believe Ray Bradley would be willing to throw out his own conclusions for ‘The Cause“. But people who become consumed with a cause throw out all sorts of morals.

What we have here is more hiding of critical scientific data to create the illusion of unprecedented warming. One of many examples in those 5,000 emails.

More on the tree-line can be found here.

5 responses so far

5 Responses to “Hiding The Medieval Warm Period”

  1. MerlinOS2 says:

    My dad used to tell me the old adage that you are entitled to your own opinion but you are not entitled to your own set of facts.

    True science takes in all known facts to form reasonable conclusions and modifies that position as facts are disproved,not just dropped. This tuning process moves us generally from first approximations to more specific knowledge as the process moves forward.

    Scientists of all areas can look at the methods here and evaluate the process even if they don’t have full mastery of the data impacts. The world science community really needs to deal with this before it infects their world with the virus this has created and cast doubt on science as a whole.

  2. sjreidhead says:

    The medieval warm-up followed a catastrophic incident around the “fall of Rome” c. 500 or so. It was probably caused by one of the Indonesian volcanos erupting and creating a multi-century global cooling. Prior to that, during the “ancient” times, the planet was a good 5-6 degrees warmer than it is now.

    What truly annoys me is the fact that when climate is studied, no one bothers with the historical record.

    The Pink Flamingo

  3. crosspatch says:

    I have a paper here around the house someplace that I read a couple of years ago concerning wood recovered from Alaskan glacier retreat. I don’t remember offhand which glacier and I will attempt to locate the paper if there is any interest but the point was that 14C dating of wood chunks and tree-ring analysis of entire logs showed that the glaciers had advanced through forested area in Alaska at some point in the 13th century. Apparently they documented two phases of advance or advance through two different forested areas. I believe one phase of advance was in the 8th century but I have been to sleep once or twice since I read that paper and my recollection might not be precise.

    Also, there is another paper concerning glacial retreat in the Alps of Switzerland where the retreating ice is exposing 5000 year old wood. So those valleys that are now glaciated were forested some 5000 years or so ago.

    AJ, there is ample evidence of the MWP and LIA in Europe, North American, South America and Africa. We see changes in the track of the Intertropical Convergence Zone during these periods that are reflected in changes in pollen counts in various lake beds and changes in O18 counts in water trapped in stalagmites and stalactites growing in limestone caverns. We also see great changes in the precipitation regime in places like China during those times where it is obvious there were major changes in monsoonal flows.

    Look, I would not trust anything put out by the discredited CRU. It is very clear they had a desired result in mind when they began their research and much energy is spent in massaging the results to meet that desire. It is agenda science. The entire CRU and the University of East Anglia has had its reputation sullied by these fools.

  4. pdtillman says:

    Thanks for continuing to dig into the CG2 emails. CA has a number of posts along these lines — notably, the subfossil tree stumps in CA Sierra lakes — documenting a warm, dry MWP — and the circumarctic evidence of subfossil/preserved wood emerging from melting glaciers — clearly indicating past plant growth under what’s now ice and glacial outwash.

    Clive Crook’s comment at the Atlantic comes to mind:
    “The closed-mindedness of these supposed men of science, their willingness to go to any lengths to defend a preconceived message, is surprising even to me…

    The stink of intellectual corruption is overpowering.”

  5. AJ

    Do you remember the old BBC on PBS documentary television series called “Connections?”

    This is the summary of episode six:

    Connections – Episode 6 – “Thunder in the Skies”

    A colder climate in the 13th century froze Greenland solid, produced icebergs in the north Atlantic; this situation in the next seven centuries changed the course of history. Buildings were erected for a colder climate; as wood became scarce, new sources of energy were necessary. The Industrial Revolution spurred advances in the steam engine and navigation, which in-turn transformed the face of the country. A pause in history later, the gasoline engine unveiled the heavens to humans.

    Details many of the changes in building construction and energy usage which occurred when the climate of Europe changed dramatically in the 13th century.He shows how the scarcity of firewood contributed to the invention of the steam engine, which was the predecessor of gasoline-powered engines used today.

    Now see this link at the 2 minute mark: