In his rebuttal to this Nick Stokes points out that the average elevation of the two sets of stations is different and that when that is taken into account, allowing a temperature drop of 6 degC/km then the difference between the two sets of data is explained.
However the original network had an average elevation of 1,681 ft (512 m) and the new network has an average of 2,223 ft (667.6 m) giving a difference of 155.6 m or an anticipated temperature difference of 0.1556 x 6 = 0.93 deg C.
Well, in the state data that I calculated some time ago I plotted the temperature against elevation and so I quickly (too quickly as I found out) went through the various posts for the different states shown undeer the Follower pictures on the right hand side of the page, and listed them with the average slopes of the graphs I had plotted. Ran an average, and posted the result on WUMT.
Turns out I made a slight error since I plotted the temperature in deg F and the elevation in meters, so that the correlation I got was in bastard units. And I mis-entered one of the data points into the table. It translates, when done correctly into an average decrease of 0.016 deg F per meter, or 0.0089 deg C per m, 8.9 deg C per km, 50% higher than that quoted by Nick.
For those interested I have tabulated the average slope against average state elevation and then plotted it, just for grins.
Figure 1. Temperature trend with average elevation for each of the Contiguous United States
What is interesting (apart from the two negative values for North and South Dakota) is how the trend shifts as one gets closer to sea level. I did not plot this relative to their actual distance from the sea, but it reinforces my conclusion that the sea temperatures have more of an influence than we are giving them credit for.
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