“Spencer’s UHI -vs- population project – an update“. Dr. Roy Spencer is already trying to re-explain yesterday’s proposed paper “proving” the nefarious Urban Heat Island effect. Anthony Watts characterizes it as “a unique and valuable analysis”, but I wouldn’t go further than “unique” myself.
Right off the bat he admits that, because it’s a too “difficult influence to correct for”, he hasn’t considered any of the local factors that are actually relevant to UHI. Details, details! His analysis is merely goofing around in Excel.
Dr. Spencer also says that he’s among those that “believe that much as 50% (or more) of the ‘global warming’ signal in the thermometer data” is a product of UHI. That’s a seriously fuzzy claim that leaves him lots of wiggle room. Too bad there have been objective statistical analyses trying to quantify just this idea and they’ve concluded that the bias is actually toward slightly under-reporting the warming. See Open Mind, Clear Climate Code, The Blackboard and Menne, 2010 (described at Skeptical Science).
How did he select his urban/rural station pairings? It seems to boil down to simple proximity, with no attempt to match geographical settings. This ignores an important environmental factor… Unless it is used behind the scenes to cherry-pick pairings for a particular result.