Okay, let me repeat what I just said to Omnologos:
No effect for UHI simply doesn’t pass the smell test. But let’s try a thought experiment. Let’s say that in 1900 you have a thermometer that is surrounded by 5 miles of concrete and asphalt in all directions. By 2000 it has 10 miles of concrete and asphalt in all directions. We’ll call this the Urban thermometer.
Then, let’s take a thermometer that is sitting in the middle of a cow pasture in 1900 and then in 2000 it is surrounded by concrete and asphalt for 500 yards. We’ll call this the rural thermometer.
Which of the two thermometers will have increased the most in temperature?
Seems to me that using the 16,000 least urban out of the 39,000 and then comparing them against the 39,000 doesn’t prove a thing. Better to use 100 thermometers that are known to have no change at all in site conditions than 16,000 that could still be effected by construction. Their method seems to suffer from the old brain dead mechanical approach combined with unverifiable assumptions that all the other sources suffer from.
And to simply conclude that UHI makes no difference? Come on – get out of my face.