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AGU December 2006 Meeting Stephen McIntyre Toronto, Canada www.climateaudit.org/pdf/agu06.ppt. The Impact of NRC Recommendations on Climate Reconstructions U11B-05. NRC Panel and M&M:. 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.
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.
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.
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”
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
Top: Spaghetti graph showing Briffa 1995 (black), Briffa 2000 (Yamal – red); Polar Urals update (Esper 2002 – blue)
Bottom- Treeline at Polar Urals (Shiyatov 1995)
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.
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
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.
Top: Three monsoon proxies used in temperature composites; right – journal titles and picture of Dulan juniper
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.