Interesting that the highest heat spikes are in the middle of Russia (Soviet Union in 1981).
I read somewhere (I wish I could find the links) that during the Soviet times, the fuel rations your city/area got were based on the temperature. Makes sense, but obviously this created a great incentive for the people recording the temperatures to fudge the numbers down so they would get more fuel.
If you look at the NOAA world temperature maps for the past 10-20 years, Siberia is always running very hot. One can only wonder how much of that heat is real vs how much is due to the fudging in the past.