The width of the tree-rings near the northern limit of the Taiga in the northern Ural Mountains is a measure summer mean temperatures. It is important to study conditions at high-latitude (i.e. about 67ºN) is that we expect global warming to become most evident there.
Tree ring data from that region since 914 AD show that summers have been warmer this century, especially during its last quarter, than ever before (1). The next warmest time was 1202-1291. There were notably cool decades between 1530-1640. The fluctuations did not coincide with those recorded in the literature for the Mediaeval Warm Period in other parts of the world, but the north Ural temperatures do match changes of the northern hemisphere average since 1400.
(1) Briffa, K.R., P.D. Jones, F.H. Schweingruber, S.G. Shiyatov and E.R. Cook 1995. Unusual twentieth-century summer warmth in a 1000-year temperature record from Siberia. Nature, 376, 156-9.