Larry Huldén of the Finnish Museum of Natural Science sent me a nice note, mentioning:
I have met Phil Jones in Helsinki during a Climate meeting. My wife had a paper on mediaeval warm period in Finland in which she showed that oak (Quercus robur) forests occurred some 150 km north of the present time limits. Finland was then practically still in the Iron age. Phil Jones tried in many ways to explain that farmers themselves had planted the oak forests, which is complete garbage.
Medieval treelines are a very interesting topic. I’ve collected information on this from time to time and will post up some things that I’ve noticed. Here’s an interesting graphic from the Polar Urals site showing treeline changes. The altitude of trees sampled also changed dramatically over the centuries.
Briffa’s temperature reconstruction from the Polar Urals is a staple of multiproxy studies by the Hockey Team. It concluded that 1032 was the "coldest year of the millennium" – a conclusion which seems inconsistent with other evidence. I’ve done a lot of work on the Polar Urals and will mention it on another occasion. I’ve tried to get information on the altitudes of individual trees in order to see what effect the changes in altitude have had on site chronologies. Naturally I can’t get this information.