1. The document summarizes key findings from an NRC panel and McIntyre's work that are critical of some climate reconstruction studies. 2. It notes that the NRC panel agreed with McIntyre that bristlecone pines are flawed proxies that should be avoided, and that some reconstructions could not claim the warmest years or decades. 3. The document also shows that just a few problematic proxies like bristlecone pines and the Yamal chronology seem to drive conclusions of modern warming being unprecedented, and that alternative reconstructions without these proxies show more comparable medieval warming.

1. 1
The Impact of NRC
Recommendations on Climate
Reconstructions
U11B-05
AGU December 2006 Meeting
Stephen McIntyre
Toronto, Canada
www.climateaudit.org/pdf/agu06.ppt

2. 2
NRC Panel and M&M:
M&M Issue NRC Panel
MBH Principal Components
Method severely biased
Agreed
Bristlecones are flawed proxies Should be “avoided”
MBH failed verification test said
to have been used
Agreed
Could not claim “warmest year” or
“warmest decade” based on data
and methods
Disallowed confidence
claims prior to 1600

3. 3
Key Recommendations and
Findings
 Precipitation-sensitive proxies e.g. “moisture-sensitive
trees and isotopes in tropical ice cores” should not be
used without “climatologic justification” of any apparent
proxy-temperature correlation;
 Strip-bark bristlecone and foxtails should be “avoided”.
 Many reconstructions are based on the same datasets
and are not independent. Some are not robust with
respect to removal of individual proxies.

4. 4
“Plausible”...
NRC panel used 4 reconstructions as comfort for comparing
modern-medieval levels, but did verify that cited reconstructions
met proxy quality standards. Medieval-modern relationship
reverses with trivial and justifiable variations in proxy selection.

5. 5
Most MBH “proxies” are
indistinguishable from high-frequency
noise. The pattern comes from
bristlecones.
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1000 1200 1400 1600 1800 2000
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1000 1200 1400 1600 1800 2000
Left – 6 MBH99 proxies. Right: top – contribution of proxy “classes”
(proxy type * continent) to MBH reconstruction, bristlecones in red.
Bottom – same with each proxy class scaled.

6. 6
Bristlecones and foxtails occupy
cold arid niche
Mooney: “bristlecone pine is
responding in gross terms primarily
to a moisture gradient in the White
Mts”. Its “main competitor” is
sagebrush.
Lloyd and Graumlich: “previous
winter precipitation is the most
important factor governing growth
variation”

7. 7
Underwater medieval trees in the
Sierra Nevadas ...
 Major long-term changes in local
hydrology;
 Lakes re-formed only in the Little
Ice Age
 Graumlich: late 20th
century “less
remarkable for warmth than for high
winter precipitation totals”

8. 8
Bristlecone/foxtail chronologies are
inconsistent with ecological temperature
estimates...
Miller et al 2006: Medieval forests on summits were “typical of forests
currently 300-500m lower”; medieval annual temperatures were “3.2 deg C
warmer than at present”.
Left: Medieval tree above treeline; right- bristlecone and foxtail ring width chronologies

9. 9
Spaghetti in the Urals
• Briffa’s Yamal chronology
inconsistent with other
chronologies;
• Inconsistent with ecological
estimates that medieval
temperatures were 2.5-3.5
deg warmer;
Top: Spaghetti graph showing Briffa
1995 (black), Briffa 2000 (Yamal –
red); Polar Urals update (Esper
2002 – blue)
Bottom- Treeline at Polar Urals
(Shiyatov 1995)

10. 10
One site can affect a reconstruction …
Blue – Briffa 2000 reconstruction using Yamal chronology; yellow
– impact using Polar Urals update. Impact on D'Arrigo et al 2006
will be similar since 5 of 6 series overlap.
800 1000 1200 1400 1600 1800 2000
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With Polar Urals Update
With Briffa Version

11. 11
O18 Decreases at Mount Logan and Law
Dome
 No rational basis for
attributing Mt Logan and
Law Dome to circulation
changes, while citing
Guliya and tropical cores
as evidence of “unusual”
temperature increases
 Panel did not discuss Law
Dome when stating that
no Antarctic sites show
medieval warming

12. 12
Spaghetti Guliya
Three different versions of Thompson’s 1992 Guliya δO18
series used in 2006 studies. Reconciliation and quality control
is a prerequisite for statistical analysis. Results from all
samples need to be archived.

13. 13
Monsoon Proxies used in
Temperature Composites
Top: Three monsoon proxies used in
temperature composites; right – journal
titles and picture of Dulan juniper

14. 14
Arbitrary selection of ocean sediment
proxies
 G. Bulloides pattern is not
characteristic of other high-
resolution sediment proxies;
 Many high-resolution ocean
proxies show distinct MWP,
even in Antarctica;
 Dating precision is insufficient
to prove or disprove
synchronization

15. 15
Seeming modern-medieval
differential depends on a very few
problematic proxies:
1. Bristlecone/foxtail ring width chronologies
2. Selection of Yamal, Siberia ring width chronology in
preference to updated Polar Urals;
3. Use of precipitation or even monsoon wind speed
proxies in temperature reconstructions –
Thompson’s Himalaya ice core isotopes; Arabian
Sea cold water G Bulloides; Dulan junipers

16. 16
A Different Spaghetti Recipe
Variations of standard reconstructions using Polar Urals
update instead of Yamal and Sargasso Sea SST instead
of G Bulloides wind speed proxy and Yakutia instead of
problematic bristlecones/foxtails.

17. 17
Conclusions:
 There are very few proxies that actually
contribute to seeming modern-medieval
differential;
 These proxies are used over and over;
 These proxies, especially bristlecones,
do not meet NRC panel
recommendations or reconcile with
ecological information;
 None of the “comfort” studies meets NRC
panel recommendations for proxy quality