Friday, 25 September 2015

Watts and Co still don't get the word global

(Update: for a better treatment of the science go to see Sou at Hotwhopper.)

it is a cliché that Americans don't know about the rest of the world, only America.  Anthony Watts keeps trying to confirm it.

Today he aims to show how wrong Michael Mann is again.  Not that he manages.  He won't.  By using a line in an abstract he hopes to show that Mann's hockey stick is wrong because a new study shows that temperature changes over the last 750 years haven't behaved as Mann said they did.

But there's a big problem.  Can you spot it?  (Spoiler alert: it's in the title of the study).
Well?  What could the problem be for Watts but not for Mann?  Yes, my readership is intelligent enough to spot that this is a study about the Pyrenees.  Watts might be a weatherman (which we don't need in order to know which way the wind blows) but he isn't going to get past first grade on geography.

To give him a hand, here's a world map with a big arrow pointing to the Pyrennees.

Here's a close up of Europe.

That's right.  The Pyrenees are a mountain range that comprises a small part of the European landmass.  It isn't the entire globe. Handily there's a map in the paper which might have told Watts something:

Here is the full abstract from the study by Esper et al (2015) (pdf):
Substantial effort has recently been put into the development of climate reconstructions from tree-ring stable carbon isotopes, though the interpretation of long-term trends retained in such timeseries remains challenging. Here we use detrended δ13C measurements in Pinus uncinata treerings, from the Spanish Pyrenees, to reconstruct decadal variations in summer temperature back to the 13th century. The June-August temperature signal of this reconstruction is attributed using decadally as well as annually resolved, 20th century δ13C data. Results indicate that late 20th century warming has not been unique within the context of the past 750 years. Our reconstruction contains greater amplitude than previous reconstructions derived from traditional tree-ring density data, and describes particularly cool conditions during the late 19th century. Some of these differences, including early warm periods in the 14th and 17th centuries, have been retained via δ13C timeseries detrending — a novel approach in tree-ring stable isotope chronology development. The overall reduced variance in earlier studies points to an underestimation of pre-instrumental summer temperature variability derived from traditional tree-ring parameters.
I have bolded the same sentence as Watts did.  The detail is in the paper.  Here's an important paragraph:
The detrended δ13C reconstruction exhibits decadal scale summer temperature variations ranging from +1.57°C in the 1390s C.E. to –1.83°C in the 1890s C.E. (Fig. 5a). The uncertainty band accompanying this reconstruction back to ~1260 C.E., the first decade represented by three trees, shows most of the temperature variations over the past 750 years did not deviate significantly from the 1961–1990 mean, however. The uncertainty band is increasing back in time as a function of the reduced replication of earlier chronology periods. Whereas more recently reconstructed temperatures (+1.01°C from 2001–2009) have been cooler than the late 14th and 15th centuries, the difference between these periods is insignificant.
Significance?  Watts, Monckton and their mates weave a lot out of significance.  Remember that the warming since year X hasn't been significant (therefore no warming, is the implication)?  Cuts both ways.  Esper and colleagues are too good at science to get carried away by their results and make cautious claims written in the usual language of science, the language that is seemingly impenetrable to a science doubter denier like Watts.  I can only guess that he didn't really read the paper, but that's not a surprise.

Esper & al make no big claims.  They certainly do not claim Mann is wrong.  Here's the conclusion:
The Spanish Pyrenees δ13C based reconstruction presented here shows warmer and more variable growing season temperatures during the Little Ice Age than previously described (Büntgen et al., 2008; Dorado Liñán et al., 2012). Developing this reconstruction required systematically removing lower δ13C values inherent to treerings younger than 200 years, that would otherwise lower the mean chronology levels during earlier periods of the past millennium, where these younger rings dominate the reconstruction. As a consequence, earlier warm periods during the late 14th and 15th centuries appear warmer, though not statistically significant, compared to the late 20th century. 
A major constraint of the new reconstruction is the substantial difference in recent temperature trends caused by post-1850 δ13C correction procedures. The correction applied here, accounting for atmospheric 13C/12C ratio and plant physiological effects, appeared most suitable as it produced a timeseries without any trend in residuals after regressing against instrumental temperatures. However, developing objective criteria for post-1850 correction, independent of the goodness of fit with instrumental target data, are needed to establish δ13C based reconstructions as an additional proxy for studying climate variations over past millennia.
 I have bolded the last sentence because there is another story there that wasn't picked up in Anthony's piece - there is a need to reconcile the instrumental record with the C13 results because there is a mismatch.

Oh, and there is nothing about global climate.

Luke in the comments points out:
This reconstruction is based on one location so it does not represent a fundamental challenge to Mann’s global reconstruction.
Anthony replies:
Mann’s MBH 98 was heavily weighted on one proxy at one location, Sheep Mountain...So, “Luke” if Mann heavily weights a proxy in one location to make a global claim, does that make it OK for him, but not for anyone else?
No, it doesn't work like that.  Mann (pdf) used more than one location. In fact, he used 415 proxies, covering quite a lot more of the globe than Esper's study.  "Heavily weights" is a value loaded term for which there is no real evidence.  It is Watts who has over egged this pudding. And using McIntyre for your support.  Is that the sound of a barrel being scraped?  I think it is.  Is this his textbook?

 Esper 2015 does not reinstate the non-missing Medieval Warm Period, nor destroy Mann.  Instead, it is more evidence, if more were needed, of how much deniers are afraid of the evidence of global reconstructions that smooth the MWP and the Little Ice Age.   Esper 2015 reports on a relatively unconfirmed technique in a truly local situation.

All in all, the usual denier fare from Anthony Watts.  Pick a paper, use it out of its scientific context to poke a denier's demon and end up with egg on his face.  A typical day in Deniersville.

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