What was done
Using tree-ring width as a proxy for temperature, the authors report temperature variations for the Asian subarctic region over the past 600 years.

What was learned
A graph of the authors' data reveals that temperatures in the Asian subarctic exhibited a small positive trend from the start of the record until about 1750.  Thereafter, a severe cooling trend ensued, followed by a 130-year warming trend from about 1820 through 1950, after which temperatures fell once again.  In considering the entire record, the authors state that the amplitude of 20th Century warming "does not go beyond the limits of reconstructed natural temperature fluctuations in the Holocene subarctic zone."

In attempting to determine the cause or causes of the temperature fluctuations, the authors report finding a significant correlation with solar radiation and volcanic activity over the entire 600-year period (R = 0.32 for solar radiation, R = -0.41 for volcanic activity), which correlation improved over the shorter interval of the industrial period -- 1800 to 1990 -- (R = 0.68 for solar radiation, R = -0.59 for volcanic activity).

What it means
It is interesting to note that in this region of the world, where climate models predict large increases in temperature as a result of the historical rise in the air's CO2 concentration, real-world data show an actual cooling trend since around 1940, when the greenhouse effect of CO2 should have been most prevalent.  And, where warming does exist in the record (between about 1820 and 1940), much of it correlates with changes in solar irradiance and volcanic activity - two factors definitely free of anthropogenic influence.  Have the climate alarmists try explaining that one to you!