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Medieval Climate on the Kola Peninsula, Russia
Reference
Hiller, A., Boettger, T. and Kremenetski, C. 2001. Medieval climatic warming recorded by radiocarbon dated alpine tree-line shift on the Kola Peninsula, Russia. The Holocene 11: 491-497.

What was done
Subfossil wood samples from the Khibiny mountains in the Kola Peninsula, Russia (67-68N, 33-34E), were analyzed in an effort to reconstruct climate change there over the past 1500 years.

What was learned
Based upon dating methods used on the subfossil wood samples, it was determined that between A.D. 1000 and A.D. 1300 the tree-line was located at least 100-140 m above its current elevation. This elevation advance, say the authors, suggests that mean summer temperatures during this "Medieval climatic optimum" were "at least 0.8C higher than today."

What it means
The authors state that "the Medieval optimum was the most pronounced warm climate phase on the Kola Peninsula during the last 1500 years," demonstrating that it was "not a local but at least a north European climatic phenomenon." We agree. It is becoming harder and harder for those who claim the Medieval Warm Period did not exist, or was a localized phenomenon, to find any support for their claim. Quite to the contrary, in fact, we have reviewed a number of papers demonstrating support for the global extent of the Medieval Warm Period, which reviews can be found in our Subject Index under the heading Medieval Warm Period.

So why all the fuss about the Medieval Warm Period anyway? In a nutshell, if it can be shown that global temperatures were warmer than they are presently at a time when CO2 concentrations were much lower, then it is very clear that something other than the ongoing rise in the air's CO2 content could be responsible for the global warming of the 20th century. If it's happened before, in essence, it can happen again.