Yesterdays Gone

Spin, spin , spin. It is very important for the climate community to discredit the Medieval Warm Period, something that they have been attempting to do for over a decade now. The infamous "Hockey Stick" graph being the most famous example. Basically it is rewriting history, a very popular past time in today's society. That is what this article from Climate Audit is about.


Trouet et al 2009: "Scuppering the Deniers"


Trouet et al (2009),Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate Anomaly, published in Reader's Digest Science a few days ago. Esper the non-Archiver is a co-author. New Scientist breathlessly reported :

Europe basked in unusually warm weather in medieval times, but why has been open to debate. Now the natural climate mechanism that caused the mild spell seems to have been pinpointed.

The finding is significant today because, according to Valerie Trouet at the Swiss Federal Institute for Forest, Snow, and Landscape Research in Birmensdorf, the mechanism that caused the warm spell in Europe – and meant wine could be produced in England as it is now – cannot explain current warming. It means the medieval warm period was mainly a regional phenomenon caused by altered heat distribution rather than a global phenomenon.

The finding scuppers one of the favourite arguments of climate-change deniers. If Europe had temperature increases before we started emitting large amounts of greenhouse gases, their argument goes, then maybe the current global warming isn't caused by humans, either.
Michael Mann told the New Scientist that the new results may imply that the situation is even worse than we thought.

If one actually reads the article, the word "regional" only occurs once

The North Atlantic Oscillation (NAO) … has a substantial influence on marine and terrestrial ecosystems and regional socio-economic activity

The word "phenomenon" is not used anywhere. Nor are the words "altered" or "heat distribution". If New Scientist is correctly reporting her statements, I did not locate anything in the article that specifically supports the reported oral summary of the conclusions. Indeed, the following sentence seems to suggest the exact opposite - that the transition from the "MCA" to the Little Ice Age was "globally contemporaneous" and, in language reminiscent of Hubert Lamb, that this was due to "a notable and persistent reorganization of large-scale oceanic and atmospheric circulation patterns":

The relaxation from this particular ocean-atmosphere state into the LIA appears to be globally contemporaneous and suggests a notable and persistent reorganization of large-scale oceanic and atmospheric circulation patterns....