Climatological base period is 1992-1998. There is always the concern that part of the observed warming is an instrumental effect of the observational sites being engulfed by our expanding cities that at times are warmer than the surrounding countryside. In his Figure 7 he shows observations made in California showing this effect. The intent here is to suggest that there is little or no warming which is a remarkable reading of the data. In truth many painstaking studies have been done to determine how great this effect might be on a global scale.
All major studies show it to be quite small.
Global surface temperatures separated into three categories, those in rural, suburban, and urban areas. This is more a result of American and European proximity to and dependence upon the North Atlantic which was cooling during that period. Reference to my Figure 3 shows that this situation has changed in the last 20 years. Since 1979, surface measurements have been augmented by observations from satellites. Thus, we have global temperature records from three altitudes in our atmosphere.