The Impact of NRC Recommendations on Climate Reconstructions U11B05

1
The Impact of NRC Recommendations on Climate
ReconstructionsU11B-05

• AGU December 2006 Meeting
• Stephen McIntyre
• Toronto, Canada
• www.climateaudit.org/pdf/agu06.ppt

2
NRC Panel and MM
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
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
Most MBH proxies are indistinguishable from
high-frequency noise. The pattern comes from
bristlecones.
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
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
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
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
Spaghetti in the Urals

• Briffas 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
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.

11
dO18 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
Spaghetti Guliya

• Three different versions of Thompsons 1992
  Guliya dO18 series used in 2006 studies.
  Reconciliation and quality control is a
  prerequisite for statistical analysis. Results
  from all samples need to be archived.

13
Monsoon Proxies used in Temperature Composites
Top Three monsoon proxies used in temperature
composites right journal titles and picture of
Dulan juniper
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
Seeming modern-medieval differential depends on a
very few problematic proxies

• Bristlecone/foxtail ring width chronologies
• Selection of Yamal, Siberia ring width chronology
  in preference to updated Polar Urals
• Use of precipitation or even monsoon wind speed
  proxies in temperature reconstructions
  Thompsons Himalaya ice core isotopes Arabian
  Sea cold water G Bulloides Dulan junipers

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
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