Tomando las imágenes del material suplementario de Mann 2008:
Y comparando con el "palo" original:
parece que el palo de hockey se ha curvado algo, y el período cálido medieval y la pequeña edad de hielo vuelven a ser reconocibles, aunque siguen apareciendo bastante difuminados.
Nos cuenta Mann:
“We find that the hemispheric-scale warmth of the past decade for the NH is likely** anomalous in the context of not just the past 1,000 years, as suggested in previous work, but longer. This conclusion appears to hold for at least the past 1,300 years”
**For the purpose of this paper, we adopt the definition of ‘‘likely’’ used by the Intergovernmental Panel on Climate Change (IPCC): i.e., that the probability of the assertion being true is estimated as between 66% and 90%.
“Conclusions are less definitive for the SH and globe, which we attribute to larger uncertainties arising from the sparser available proxy data in the SH.
Given the uncertainties, the SH and global reconstructions are compatible with the possibility of warmth similar to the most recent decade during brief intervals of the past 1,500 years.”
La imagen que aparece en el artículo en sí es estilo spageti:
La actual reconstrucción de Mann corresponde con las tres primeras líneas, que aparecen con sus bandas de incertidumbre. Sobre todo habría que seguir la verde y la negra. El resto de líneas corresponden a otras reconstrucciones anteriores. La línea roja (y la gris) que aparecen al final son el registro instrumental, superpuesto a la reconstrucción, de tal forma que oculta parcialmente las líneas correspondientes a esta.
No obstante, parece que sigue habiendo una divergencia notable, de al menos 0,4ºC aunque Mann indica que el
problema de la divergencia se habría solucionado bastante en esta nueva reconstrucción:
“the known ‘‘divergence problem’’, wherein the temperature
sensitivity of some temperature-sensitive tree-ring data appears
to have declined in the most recent decades. Interestingly,
although the elimination of all tree-ring data from the proxy dataset
yields a substantially smaller divergence bias, it does not eliminate
the problem altogether (Fig. 2B). This latter finding suggests that
the divergence problem is not limited purely to tree-ring data, but
instead may extend to other proxy records. Interestingly, the problem is greatly diminished (although not absent—particularly in the older networks where a decline is observed after _1980) with the EIV method, whether or not tree-ring data are used (Fig. 2 C andD)”
Esta es otra aproximación reciente al problema:
"…the need for vegetation-based climate reconstructions to incorporate the effects of changes in atmospheric CO2 concentration, especially when attempting to compare late 20th-century reconstructed temperatures with reconstructed temperatures of the Roman and Medieval Warm Periods and the Holocene Climatic Optimum. Until this common deficiency is corrected, truly valid comparisons between these earlier times and the present cannot be made, for without properly adjusting for the growth- and water use efficiency-enhancing effects of the historical increase in the air's CO2 content, reconstructed 20th-century temperatures — which must be used in place of actual measured values when making comparisons with earlier reconstructed temperatures — will be artificially inflated."Ref: Gonzales, Leila M., John W. Williams, Jed O. Kaplan, 2008. Variations in leaf area index in northern and eastern North America over the past 21,000 years: a data-model comparison. Quaternary Science Reviews Vol. 27, No 13-14, pp. 1453-1466, July 2008
http://www.co2science.org/articles/V11/N36/EDIT.phpYa veremos qué nos van contando.
De paso, pongo también una imagen elaborada por vigilant (espero que no le importe) con todas las reconstrucciones del anterior spaghetti (excepto las actuales de Mann) y además la de Loehle. También incluye una línea rosa que es la media de todas las reconstrucciones:
https://foro.tiempo.com/climatologia/articulos+cientificos+en+contra+del+calentamiento+antropogenico-t65417.132.html
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