When I started posting about how GHCN and GISS were altering the historical temperature record a few years ago, many thought I was making it up. Things have now gone well past that stage now, and now GISS actually offer a tool to chart actual and adjusted temperatures. Below are the stations in Greenland, Iceland and Arctic Norway, which have data going back prior to 1950, and where historical temperatures have been adjusted downwards. No stations in this part of the world have been adjusted in the opposite direction, and only one, Vardo, has been left unaltered.
Needless to say, GHCN have either been unable or unwilling to explain the reason for these adjustments.
It is also worth noting that temperatures across all these stations were, generally speaking, as high in the 1930s and 40s as they have been recently.
Source: Not A Lot Of People Know That