It is pretty clear that the hedgehogs of the world understand what the hyenas don't, that given enough measurements the imperfections in individual weather stations average out and you are left with reliable trends, at least if you understand what area averaging is and how to correct for things like the time of day that different folks measure at. John V (in the comments, and the graphs have disappeared in the reorganization of the site, here they are, thanks to Valtteri Maja and Zeke Hausfather) at Climate Audit and later at Hyena Watt's place figured that out early when he compared the trends in the best and the worst stations and found essentially no difference..
However, there are surprises. The bunnies bring words in several threads at Rabett Run that Matthew J. Menne, Claude N. Williams, Jr., and Michael A. Palecki from the NOAA/National Climatic Data CenterNational Climate Data Center have been looking at dirty pictures of weather stations in the US Historical Climatology Network (USHCN), and those in the carefully sited, but new US Climate Reference Network (USCRN) and come to the conclusion:
Recent photographic documentation of poor siting conditions at stations in the U.S. Historical Climatology Network (USHCN) has led to questions regarding the reliability of surface temperature trends over the conterminous U.S. (CONUS). To evaluate the potential impact of poor siting/instrument exposure on CONUS temperatures, trends derived from poor and well-sited USHCN stations were compared. Results indicate that there is a mean bias associated with poor exposure sites relative to good exposure sites; however, this bias is consistent with previously documented changes associated with the widespread conversion to electronic sensors in the USHCN during the last 25 years. Moreover, the sign of the bias is counterintuitive to photographic documentation of poor exposure because associated instrument changes have led to an artificial negative (“cool”) bias in maximum temperatures and only a slight positive (“warm”) bias in minimum temperatures. These results underscore the need to consider all changes in observation practice when determining the impacts of siting irregularities. Further, the influence of non-standard siting on temperature trends can only be quantified through an analysis of the data. Adjustments applied to USHCN Version 2 data largely account for the impact of instrument and siting changes, although a small overall residual negative (“cool”) bias appears to remain in the adjusted maximum temperature series. Nevertheless, the adjusted USHCN temperatures are extremely well aligned with recent measurements from instruments whose exposure characteristics meet the highest standards for climate monitoring. In summary, we find no evidence that the CONUS temperature trends are inflated due to poor station siting.