Here is a discussion and an example of temperature adjustment being done by US researchers, either NASA/GISS or NOAA/NCDC (it could have been either, or both). I’ve studied the apocalyptic AGW hypothesis since the late 80’s, and I have been amazed at how the temperature from many years ago is continually revised downward. I agree that the accuracy bound of the instruments was probably larger than the temperature change that has occurred over 100 years, but how could current researchers possibly figure out that the old data had a bias that could be precisely established now? Personally I think that the most generous explanation is that the researchers are suffering from a confirmation bias. I saw that a lot in my system engineering career, particularly in missile failure investigations