evidence: In the remainder of this post, "raw data" refers to data that passed the quality-control tests (unflagged). Flagged data is discarded by the models and replaced with an invalid value (-9999). [...] The estimates produced by NOAA for the GHNC data introduce a warming trend of approximately a quarter degree C per century. Those estimates are produced at a slightly higher rate for non-rural stations than rural stations over most of the record. During the first 60 years of the record measurements were estimated at a rate of about 75%, with the rate gradually dropping to 40% in the early 1990s, followed by a brief spike in the rate before resuming the drop to its present level. Approximately 7% of the raw data is discarded. If this data were included as-is in the final record it would likely introduce a warming component from 1880 to 1950, followed by a cooling component from 1951 to the present.