Looks like denial is fading -- to be replaced by attempts to make it sound insignificant. Michael Mann and his bristlecone pines no longer cut it apparently. This is the latest attempt to prove that the MWP was a merely local phenomenenon. A local phenomenon that lasted 300 years? But recent discoveries of contemporaneous warming in New Zealand and Argentina blow the pretence off the map, of course. See here and here. Amusing that they call it an anomaly rather than a warm period, though. That rather sounds like prejudging the case. (Yes. I know that "anomaly" is climate-speak for "deviation" but I think the point still holds)

During the Medieval Climate Anomaly (approximately 800 to 1300 A.D.) temperatures in Europe were generally warmer than immediately before or after. The source of that warmth is hotly debated. Trouet et al. (p. 78) present a reconstruction of the North Atlantic Oscillation--the dominant mode of atmospheric circulation variability in the North Atlantic region--that extends back to the middle of the Medieval Climate Anomaly, based on data from Moroccan tree rings and a Scottish stalagmite. The North Atlantic Oscillation, it seems, was in a persistently positive state during the Medieval Climate Anomaly. The authors suggest that prevailing La Niña-like conditions during medieval times was initiated by high levels of irradiance and amplified by enhanced Atlantic Meridional Overturning Circulation.


Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate Anomaly

By Valerie Trouet et al.


The Medieval Climate Anomaly (MCA) was the most recent pre-industrial era warm interval of European climate, yet its driving mechanisms remain uncertain. We present here a 947-year-long multidecadal North Atlantic Oscillation (NAO) reconstruction and find a persistent positive NAO during the MCA. Supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker NAO conditions into the Little Ice Age (LIA). Globally distributed proxy data suggest that this NAO shift is one aspect of a global MCA-LIA climate transition that probably was coupled to prevailing La Niña–like conditions amplified by an intensified Atlantic meridional overturning circulation during the MCA

Science 3 April 2009: Vol. 324. no. 5923, pp. 78 - 80

Posted by John Ray. For a daily critique of Leftist activities, see DISSECTING LEFTISM. For a daily survey of Australian politics, see AUSTRALIAN POLITICS Also, don't forget your daily roundup of pro-environment but anti-Greenie news and commentary at GREENIE WATCH . Email me (John Ray) here

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