Suppose you have four temperature stations in a relatively small geographical area, and you add a fifth in the geographic middle of the group. Should the trend change?
No, it shouldn’t. The addition of the fifth station might cause the average temperature of the group to shift due to differences in local geography, but it shouldn’t affect the trend much. This is because the temperature trend in the geographic middle of the group should be about the same as the numerical average of the trend at the other four stations.
Adding 5th station not effecting trend? That is an awfully sweeping statement. I would accept it if you were talking about the USCRN high accuracy stations but not necessarily for one of the back yard, sewage treatment plant, or parking lot kind stations in the historic network.
Istm that if you average two stations, you are creating a virtual station between them,
and its trend will be an average of the trends of the two real stations.
What adding a 5th station will do, depends on its position relative to the other four.
Well, if the 5th is in the center of an urban heat island, and the time scale extends over the period when the population grew from the horse and buggy days of 15,000 to current 1.25 million . . .
I agree as long as Hansen, Mann, Jones et al had nothing to do with the installation.
If those new stations are placed in areas with expanding infrastructure, and the existing stations are not, they could.
The population surrounding Dulles Airport outside Washington, DC has increased exponentially since the 1970’s. Population around National Airport has changed much less. Yet National
maxiimum temperatures are now much hotter relative to Dulles than before. Does anyone smell something fishy going on?