As I understand it one (of many) “adjustments” made to the raw data is for things like changing land use patterns around the data collection station. Farms are warmer than forest, towns warmer than farms,etc. Problem is, many of the adjustments made to the data are bigger than the trends the so-called “scientists” purport to have found in the data. All they’re really finding are second or third order effects in their adjustments.
Nobody gets grant money from saying "we just don't have accurate enough data to draw any valid conclusions from it".