Shooting the Messenger with Blanks

As detailed in previous blog posts (Wegman-gate: Alert Congress & the Media and Science by Error and Trial), and by this recent Washington Post letter from Rep. Joe Barton (R-TX), Dr. Michael E. Mann is once again being questioned (attacked) about his paleoclimatology research.  I thought it might be constructive to see how Dr. Mann’s published work stacks up against other, more recent temperature reconstructions.

Date: 1999
Authors: Mann, Bradley, Hughes
Methodology: Principal Components Analysis (PCA) – Northern Hemisphere
Plot:

MBH99 graph as shown in the 2001 IPCC report

Summary: Hockey stick shape.  Warmer Medieval Warm Period (MWP) followed by cooler Little Ice Age (LIA) and significantly warmer temperatures in the modern era.

Controversy: This is the plot that gets all of the attention.  This is the plot that the National Research Council (NRC) investigated in 2006 at the request of Congress.  The NRC supported the scientists and their conclusions.  This is the plot that the Wegman Report has criticized as being severely flawed.  This is the plot that Virginia Attorney General Ken Cuccinelli claims may have been the result of nefarious activity on the part of Dr. Mann while he was at University of Virginia.  And this is the chart that Rep. Joe Barton claims “that Mr. Mann’s global warming projections were rooted in fundamental errors of methodology that had been cemented in place as “consensus” by a closed network of friends.”

DO THE CLAIMS OF BARTON, WEGMAN, AND CUCCINELLI STAND UP?
SINCE 1999, HAS MANN’S WORK BEEN VERIFIED BY OTHERS?

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Date: 2008
Authors: Mann, Zhang, Hughes, Bradley, Miller, Rutherford, Ni
Methodology: Composite plus scale (CPS) in orange color and RegEM-based EIV estimation in black color – Northern Hemisphere
Plot:

  

Mann et al. (2008) temperature reconstruction.

Summary: Using two differing methodologies (CPS & EIV), and whether tree rings were included or not, the plot has a hockey stick shape.  Warmer MWP followed by cooler LIA and significantly warmer temperatures in the modern era.
 

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Date: 2008
Authors: Huang, Pollack, Shen
Methodology: Direct temperature measurement from boreholes – Global
Plot:

Direct T measurement from boreholes

Summary: A broad cool minimum around AD 200 that was followed by a warming that peaked AD 1200–1400 (MWP); a subsequent cooling to a minimum around AD 1700–1800 (LIA); followed by rapid and substantial warming. “None of the borehole reconstructions show MWP peak temperatures as high as late 20th century temperatures.”

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Date: 2009
Authors: Kaufman, Schneider, McKay, Ammann, Bradley, Briffa, Miller, Otto-Bliesner, Overpeck, Vinther, Abbott, Axford, Bird, Birks, Bjune, Briner, Cook, Chipman,Francus, Gajewski, Geirsdóttir, Hu, Kutchko, Lamoureux, Loso, MacDonald, Peros, Porinchu, Schiff, Seppä, Thomas
Methodology: Composite plus scale (CPS) – Northern Hemisphere above 60^o N latitude
Plot:

Kaufmann et al. (2009)

Kaufmann et al. modified by University Corporation for Atmospheric Research

Summary: Hockey stick.  A pervasive cooling in progress 2000 years ago continued through the Middle Ages and into the Little Ice Age. “The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2000-year-long reconstruction occurring between 1950 and 2000.”

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Date: 2010
Authors: Thibodeau, de Vernal, Marcel, Mucci
Methodology: Isotopic analysis (oxygen isotopes) of shells recovered from sediments of North Atlantic Ocean
Plot:

Thibodeau et al. (2010) T plot. The grey lines to the left of the graph are ignored due to disturbance by the coring process.

Summary:  Hockey stick.  “…it is unquestionable that the last century has been marked there by a warming trend having no equivalent over the last millennium.”

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Date: 2010
Author: Ljungqvist
Methodology: Composite plus scale (CPS) - Northern Hemisphere extra-tropics (90–30°N)
Plot:

Ljungqvist T reconstruction (Source: Skeptical Science)

 

Summary: Hockey stick.  “Our temperature reconstruction agrees well with the reconstructions by Moberg et al. (2005) and Mann et al. (2008) with regard to the amplitude of the variability as well as the timing of warm and cold periods, except for the period c. ad 300–800, despite significant differences in both data coverage and methodology.”  “The temperature of the last two decades, however, is possibly higher than during any previous time in the past two millennia…”

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DR. MANN’S WORK HAS BEEN VERIFIED BY MANY OTHER SCIENTISTS

The hockey stick-shape temperature plot that shows modern climate considerably warmer than past climate has been verified by many scientists using different methodologies (PCA, CPS, EIV, isotopic analysis, & direct T measurements).

To believe Rep. Joe Barton and Attorney General Ken Cuccinelli one must also believe in magic.  Consider the odds that various international scientists using quite different data and quite different data analysis techniques can all be wrong in the same way.  What are the odds that a hockey stick is always the shape of the wrong answer?

The only reasonable conclusion is that Barton and Cuccinelli are
shooting the messenger with blanks.

It is time for you two gentleman to do some constructive work.

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Update (10/17/2010): Science committee responds to Rep. Joe Barton – Dr. Gerald North corrects Barton’s mistakes.  North was Chair of the National Research Council’s Committee on Reconstruction of Surface Temperatures for the Last 2000 Years, mandated by Congress in 2006.