Mann's hockey stick disappears – and CRU's Briffa helps make the MWP live again by pointing out bias in the data

Shock, awe. Untruncated and unspliced data used in a new paper from Briffa and Melvin at UEA restores the Medieval Warm Period while at the same time disappears Mann’s hockey stick. Here’s figure 5 that tells the story:

Figure 5. Temperature reconstructions created using the 650-tree (‘alltrw’ data) TRW chronology (a) and the 130 tree (‘S88G1112’ data) MXD chronology (b). Chronologies were created using two RCS curves and were regressed against the Bottenviken mean May–August monthly temperature over the period 1860 to 2006. The shaded areas show two standard errors (see SI15, available online, for details) plotted either side of the mean where standard errors were scaled to fit the temperature reconstruction. The TRW and MXD temperature reconstructions of (a) and (b) are compared in (c) after they were normalised over the common period 600 to 2008 and smoothed with a 10 year spline. The lower two panels compare the reconstructions using the TRW chronology (d) and MXD chronology (e) with the mean of May to August monthly temperature from Bottenviken over the period 1860 to 2006.

Look at graph 5c, and you’ll see 20th century warmth matches peaks either side of the year 1000, and that for the TRW chronology 20th century warmth is less than the spike around 1750. This puts 20th century (up to 2006 actually) warmth in the category of just another blip. There’s no obvious hockey stick, and the MWP returns, though approximately equal to 20th century warmth rather than being warmer.

Whoo boy, I suspect this paper will be called in the Mann -vs- Steyn trial (if it ever makes it that far; the judge may throw it out because the legal pleading makes a false claim by Mann). What is most curious here is that it was Briffa (in the Climategate emails) who was arguing that some claims about his post 1960 MXD series data as used in other papers might not be valid. It set the stage for “Mikes Nature trick” and “hide the decline“. Steve McIntyre wrote about it all the way back in 2005:

Post-1960 values of the Briffa MXD series are deleted from the IPCC TAR multiproxy spaghetti graph. These values trend downward in the original citation (Briffa [2000], see Figure 5), where post-1960 values are shown. The effect of deleting the post-1960 values of the Briffa MXD series is to make the reconstructions more “similar”. The truncation is not documented in IPCC TAR.

I have to wonder if this is some sort of attempt to “come clean” on the issue. Mann must be furious at the timing. There’s no hint of a hockey stick, and no need to splice on the instrumental surface temperature record or play “hide the decline” tricks with this data.

Bishop Hill writes:

Well, well, well.

In its previous incarnation, without a MWP, the series was used in:

  • MBH98
  • MBH99
  • Rutherford et al 05
  • Jones 98
  • Crowley 00
  • Briffa 00
  • Esper 02
  • Mann, Jones 03
  • Moberg
  • Osborn, Briffa 06
  • D’Arrigo et al 06

It rather puts all that previous work in perspective, since this new paper has identified and corrected the biases. It should be noted though that tree ring paleoclimatology is an inexact science, and as we’ve seen, even a single tree can go a long way to distorting the output. On the plus side, it is good to see that this paper defines and corrects biases present in the MXD and TRW series of the Tornetraesk tree ring chronology dataset. This is a positive step forward. I suspect there will be a flurry of papers trying to counter this to save Mann’s Hockey Stick.

From the journal Holocene:

Potential bias in ‘updating’ tree-ring chronologies using regional curve standardisation: Re-processing 1500 years of Torneträsk density and ring-width data

Thomas M Melvin University of East Anglia, UK

Håkan Grudd Department of Physical Geography and Quaternary Geology, Stockholm University, Sweden

Keith R Briffa University of East Anglia, UK

Abstract

We describe the analysis of existing and new maximum-latewood-density (MXD) and tree-ring width (TRW) data from the Torneträsk region of northern Sweden and the construction of 1500 year chronologies. Some previous work found that MXD and TRW chronologies from Torneträsk were inconsistent over the most recent 200 years, even though they both reflect predominantly summer temperature influences on tree growth. We show that this was partly a result of systematic bias in MXD data measurements and partly a result of inhomogeneous sample selection from living trees (modern sample bias). We use refinements of the simple Regional Curve Standardisation (RCS) method of chronology construction to identify and mitigate these biases. The new MXD and TRW chronologies now present a largely consistent picture of long-timescale changes in past summer temperature in this region over their full length, indicating similar levels of summer warmth in the medieval period (MWP, c. CE 900–1100) and the latter half of the 20th century. Future work involving the updating of MXD chronologies using differently sourced measurements may require similar analysis and appropriate adjustment to that described here to make the data suitable for the production of un-biased RCS chronologies. The use of ‘growth-rate’ based multiple RCS curves is recommended to identify and mitigate the problem of ‘modern sample bias’.

Here’s the money quote from the paper:

If the good fit between these tree-growth and temperature data is reflected at the longer timescales indicated by the smoothed chronologies (Figures 5c and S20d, available online), we can infer the existence of generally warm summers in the 10th and 11th centuries, similar to the level of those in the 20th century.

Conclusions

• The RCS method generates long-timescale variance from

the absolute values of measurements but it is important to

test that data from different sources are compatible in

order to avoid systematic bias in chronologies.

• It was found in the Torneträsk region of Sweden that there were systematic differences in the density measurements from different analytical procedures and laboratory conditions and that an RCS chronology created from a simple combination of these MXD data contained systematic bias.

• Both the known systematic variation of measurement values (both TRW and MXD) by ring age and the varying effect of common forcing on tree growth over time must

be taken into account when assessing the need to adjust subpopulations of tree-growth measurements for use with RCS.

• It was necessary to rescale the ‘update’ density measurements from Torneträsk to match the earlier measurements over their common period, after accounting for ring-age decay, in order to remove this systematic bias.

• The use of two RCS curves, separately processing fastand slow-growing trees, has reduced the effect of modern sample bias which appears to have produced some artificial inflation of chronology values in the late 20th century in previously published Torneträsk TRW chronologies.

• A ‘signal-free’ implementation of a multiple RCS approach to remove the tree age-related trends, while retaining trends associated with climate, has produced

new 1500-year long MXD and TRW chronologies which show similar evidence of long-timescale changes over

their full length.

• The new chronologies presented here provide mutually consistent evidence, contradicting a previously published conclusion (Grudd, 2008), that medieval summers (between 900 and 1100 ce) were much warmer than those

in the 20th century.

• The method described here to test for and remove systematic bias from RCS chronologies is recommended for further studies where it is necessary to identify and mitigate systematic bias in RCS chronologies composed of nonhomogeneous samples.

Advertisements

  Subscribe  
newest oldest most voted
Notify of

Not only has the Hockey stick disappeared, but so have the Grand Solar Minima and Maxima correlations…

AlanG

But. But. If I want my trees to grow more I water them. Why this dendrothermometry?

theduke

I can hear Rosanne Rosannadanna now: “Never mind.”

Jimbo
Harold Ambler

Color me happy.

Crispin in Kuala-Lumpur

@Leif
Well spotted.

What a news!

What’s the betting that this paper will make it on to the forthcoming BBC Radio thing on Climategate?

The warm is turning.

Kevin Kilty

Picking a nit…”throw” it out, not “through” it out.
[Already fixed. — mod.]

If you Halloween was incomplete without some Climate Science Comedy treats…
see “Penn Pied Piper Plays Laureate” for a satirical look at current events….
WARNING…do to the banal nature of current culture, this satire contains gratuitous
use of double-entendre and was processed by equipment previoulsy used on NUTS.
Trick or Treat here…. http://fauxscienceslayer.com/pdf/Penn_Pied_Piper.pdf

son of mulder

I still have no faith in tree rings as a proxy for global temperature. I think it’s a waste of money that could be better spent on real science. What sort of denier or sceptic does that make me?

Leif, Maunder started at 1645. Graph (b) has 1645 4C colder than now.
Admittedly the cold started around 1600, warmed a bit and then made a big dip back to 8C. But it was cold. Very cold.

MangoChutney

Are trees good thermometers?
I’m not so sure, so this paper could merely be another attempt to have trees accepted as a good proxy for historical temperatures – how long will it take for Mann to spot the “fatal flaw” in this paper?
I’d be really interested to know who reviewed this paper.
Also, this paper doesn’t make it into AR5, does it?

Think there’s a chance that the authors are irritated at the glowing attention that Mann and Hansen preen over for publishing nonsense and this is a passive aggressive way of shutting them up and getting back to reality?

Could it be, reading between the lines, that Dr. M. Mann may be becoming too much of an embarrassment for the ‘team’?

Erik Christensen

Hockey Stick, return to sender:
Hit Me With My Hockey Stick
Hit me, hit me, hit me
Hit me slowly, hit me quick
Hit me, hit me, hit me

One more nail in the “Treemometer” coffin. I’d say this calls for a little drinkeepoo… (Waiter!)

joeldshore

Ah…Isn’t this just a temperature reconstruction from one area,,,Northern Sweden? I don’t necessarily see any contradiction whatsoever with the work of Mann et al., which showed that although many individual regions experienced similar warmth to modern warmth sometime in some broadly-defined “Medieval Warm Period”, the warmest times were asynchronous in different regions and, hence, when you looked globally the warmth was not as great as the late 20th century warmth which was not asynchronous.
It helps to understand carefully what someone’s work actually said before jumping to the conclusion that a new piece of work contradicts it!
REPLY: Oh, please. You really are a myopic sorts aren’t you? By your logic then we should ignore Yamal, and the infamous YAD061 sample becuase it is too local. That seemed fine for these scientists purposes before.
The truth is that Mann’s hockey stick is a fabrication, he’s “embellished” it, just like he did his Noble Prize claims, and there are other papers that confirm that the MWP is as warm or warmer than today, such as
Christiansen of the Danish Meteorological Institute and F C Ljungqvist of Stockholm University.
http://wattsupwiththat.com/2012/10/17/new-paper-confirms-the-climate-was-warmer-1000-years-ago/
Esper et al in the Journal of Global and Planetary Change
http://wattsupwiththat.com/2012/10/18/yet-another-paper-demonstrates-warmer-temperatures-1000-years-ago-and-even-2000-years-ago/
But you’ll poo poo those too. because that’s what you do as a defender of the faith….a faith that is now dying a slow sure death. Go ahead spin furiously, because nobody but the faithful believes in the embellished dendro claims of the team anymore.- Anthony

Pamela Gray

Most major-journal papers worth their self-imposed sense of integrity would thank contributing sources used in the development and conclusion of the study. So. I would ask, is WUWT properly thanked at the end? I was just a low-life freshman researcher but had the honest integrity to include my gratitude in the area of Auditory Brainstem Response research. As you get older or well-known, does this obligation become unnecessary? I think not. Briffa owes a debt of gratitude to WUWT. I wonder if he has the honest type of integrity necessary to do the right thing. And to do it here.
Come on Briffa, what say you?

Pamela Gray

By the way, my research thesis, published and archived in the Oregon State University library, includes such thanks but when my paper was published in a major journal, the citation of the debt I owed was removed by the higher-up laboratory powers-that-be I worked for before it got published. So apparently, my observation about when your lose your honest integrity appears to be valid.

Is the house of cards falling? All those papers that referenced old “data”. My MY.

bee bop

We are talking about Sweden, right?

Bloke down the pub

Now Keith, isn’t that a weight off your chest?

Peter Miller

Not a great day for ‘climate science’, as practiced by Mann, Hansen and others.
But perhaps a good day for those few who practice real climate science.
More important is this: it may be the start of a long ovedue process of ‘climate science’ becoming honest under the relentless pressure of sceptics exposing the distorted data and manipulated conclusions of the high priests of the CAGW cult.

The famous Mann-ufactured AGW-promoting “Hockey Stick” is dead! Long live the King of global hoaxes!

Gunga Din

Hey, Mikey! Your bus is here!
(Now all we need is a certain password.)
PS to Briffa, Thanks for being honest about what you see. The repercussions will pass. What you see in the mirror won’t.

RockyRoad

son of mulder says:
October 28, 2012 at 11:45 am

I still have no faith in tree rings as a proxy for global temperature. I think it’s a waste of money that could be better spent on real science. What sort of denier or sceptic does that make me?

Logical.

sunshinehours1 says:
October 28, 2012 at 11:51 am
Leif, Maunder started at 1645. Graph (b) has 1645 4C colder than now.
One should look at graph (c), not the individual years. And some people would say that now is the warmest on record in spite of solar activity being the lowest in a hundred years. But, for true believers, cheery picking always works their way. One way out is to claim that tree-ring data is nonsense, but that also makes nonsense that there was a ‘decline’ to hide.

D Böehm

joelshore says:
“I don’t necessarily see any contradiction whatsoever with the work of Mann et al., which showed that although many individual regions experienced similar warmth to modern warmth sometime in some broadly-defined “Medieval Warm Period”, the warmest times were asynchronous in different regions and, hence, when you looked globally the warmth was not as great as the late 20th century warmth which was not asynchronous.”
Wrong. As we can see in this overlay of Antarctic, Greenland, and Arctic ice cores, global temperatures were synchronous — which includes the MWP.
There is always regional variability, which makes for easy [and wrong] cherry-picking. But globally temperatures are synchronous in both hemispheres, as the ice core records make clear.

RockyRoad

joeldshore says:
October 28, 2012 at 12:02 pm

It helps to understand carefully what someone’s work actually said before jumping to the conclusion that a new piece of work contradicts it!

You wouldn’t contradict Mann’s work if a hundred… nay, a thousand pieces of work contradicts it, joel. Some people are just stuck.
But then, Mann has every reason to be honest, doesn’t he? Or are you missing the gist of Mann’s suit against Steyn?
Stay stuck if you want while the rest of the world moves on.

J Martin

Leif Svalgaard said on October 28, 2012 at 11:21 am “Not only has the Hockey stick disappeared, but so have the Grand Solar Minima and Maxima correlations…”
A step in the right direction nonetheless. Just watch the solar min’s and max’s reappear when it starts to get very cold. Ten years ? Will Briffa have retired by then ? In which case someone else will do it.
Wanted. A new H Lamb, for a post not yet on the job market, but surely will be once global warming turns out to be sustained serious cooling.

Leif Svalgaard says:
October 28, 2012 at 11:21 am
Not only has the Hockey stick disappeared, but so have the Grand Solar Minima and Maxima correlations…

Not at all Leif, everything fits nicely. My Solar derived proxy for ocean heat content is right on target:
http://tallbloke.wordpress.com/2012/10/17/phil-jones-we-dont-know-what-natural-variability-is-doing/

Naturally , the paper is too late for inclusion in AR5e ,
Where we will be treated to several hockeysticks I have no doubt.

The hockey stick is dead! Long live the king of global hoaxes!

Pamela Gray

Leif, your logic is such ear candy. If tree-ring data is good, it shouldn’t deviate, if it is bad, it doesn’t matter. Priceless.

Edim

“Not only has the Hockey stick disappeared, but so have the Grand Solar Minima and Maxima correlations…”
I see correlations.
http://upload.wikimedia.org/wikipedia/commons/2/28/Sunspot_Numbers.png

AlexS

And the warmists and the so called “skeptics” discuss one more time an unreliable, localized temperature proxy…

Alexej Buergin

Et tu, Briffa.
But that would compare the IPCC to Caesar, who was a great man.

richardscourtney

son of mulder
At October 28, 2012 at 11:45 am you ask:

I still have no faith in tree rings as a proxy for global temperature. I think it’s a waste of money that could be better spent on real science. What sort of denier or sceptic does that make me?

A compatriot with me.
Richard

Graeme M

“I don’t necessarily see any contradiction whatsoever with the work of Mann et al., which showed that although many individual regions experienced similar warmth to modern warmth sometime in some broadly-defined “Medieval Warm Period”, the warmest times were asynchronous in different regions and, hence, when you looked globally the warmth was not as great as the late 20th century warmth which was not asynchronous.”
Is this true, that 20th C warming is not asynchronous? I have seen the plots of global anomalies, but not the actual local records for the various continents etc. I DO know there is much controversy over local records, eg the Australian and NZ temp records for the past 100 years. I have done wolfram alpha plots o actual temp records for many countries and find very few cases of upwards trends but I have no idea how accurate those plots are.

richardscourtney says:
October 28, 2012 at 12:46 pm
son of mulder
At October 28, 2012 at 11:45 am you ask:
“I still have no faith in tree rings as a proxy for global temperature. I think it’s a waste of money that could be better spent on real science. What sort of denier or sceptic does that make me?”
A compatriot with me.
Richard

I think there may be a link of sorts between temperature and tree ring width, mostly mediated by changes in rainfall and the temperature dependency of co2.
So, pretty tenuous. I trust Loehle’s non-tree-ring temperature proxy more.

Edim says:
October 28, 2012 at 12:37 pm
I see correlations.
Of course you do. True believers always do. For them, everything fits nicely, no matter what the data says.

tallbloke says:
October 28, 2012 at 12:34 pm (Edit)
Naturally , the paper is too late for inclusion in AR5e ,
Where we will be treated to several hockeysticks I have no doubt.
######################
tallbloke why do you spread this nonsense without even checking. The Melvin paper is cited in the Second Order Draft. The only deadline that really matters is the “accepted” deadline which doesnt happen until 2013. The most recent deadline merely stated that the papers had to be submitted.
Sheesh. Does anybody here check facts.

Steven Mosher says:
October 28, 2012 at 12:57 pm
tallbloke why do you spread this nonsense without even checking.
TB always spreads nonsense, to wit his comments upthread. Best thing is to just ignore it.

stephen richards

I seem to remember way back that Steve Mc detected a certain reticense in Briffa at some point. Sort of, like Briffa was embarrassed by Mann and was looking for a way out.

Leif,
Not sure if you are a reviewer or not but the SOD has some nice work on MWP/LIA and solar forcing studies. of course for those who think their science is settled ( the sun dunnit ) the actual science may not be of interest. hehe.

Dajake

I thought it was decided that all warming was global and all cooling was regional.

Steven Mosher says:
October 28, 2012 at 1:04 pm
Not sure if you are a reviewer or not but the SOD
I’m not. I only try to make sure that the solar data is correct [hard enough with people wanting to cherry pick old, obsolete, invalid ‘data’]. Actual science usually is of minor interest compared to the ’cause’, whatever that might be.

joeldshore

D Boehm says:

Wrong. As we can see in this overlay of Antarctic, Greenland, and Arctic ice cores, the MWP was globally synchronous.

Ah…As near as I can tell (because you have presented a graph with no context and even no labels on the axes), what you are showing is a graph over the last 100,000 years. If you can pick out something that happened 1000 years ago on such a graph, you have better eyes than I.
Anthony says:

Oh, please. You really are a myopic sorts aren’t you? By your logic then we should ignore Yamal, and the infamous YAD061 sample becuase it is too local. That seemed fine for these scientists purposes before.

I didn’t say this sample can be ignored. I just said it alone does not a global or hemispheric reconstruction make. Neither does Yamal. Can you show me where anyone has claimed it does?
Look, I don’t claim to know for sure whether the modern Northern hemispheric temperatures are definitely warmer than they were during the MWP or not. Most full hemispheric reconstructions have found they are; a few, such as those other two you mentioned, have apparently found the MWP temperature comparable. And, unlike many around here, I let science, rather than my own preconceptions, drive the conclusions.
However, citing a paper regarding a temperature record at one location as if it contradicts work regarding the entire hemispheric temperature record is just wrong, pure and simple. And, defending it while claiming that some respected scientist’s work is a “fabrication” is just the pot calling the kettle…