Joe D’Aleo at Anthony Watts climate sceptics “supersite” report on trend differences 1948-2011 in Texas cities compared to Texas as a whole. Of course the cities are warming compared to the State. And yes of course Texas cities non-climatic warming trends are incorporated into “GLOBAL WARMING”. There is a link to this NOAA page – maybe some readers can do similar comparisons with other States, I suggest looking in States with flat terrain will make it easier to detect UHI. In 2000 I reported on Jones 1994 additions of large Texas cities. I also found plenty of evidence of UHI contamination in IPCC trends from other USA cities. Hotlanta – a great example seems to have been left off my list page. I recall asking Phil Jones about his use of Atlanta and he replied that in his 1994 update he included some other smaller places from Georgia. As though that could cancel the colossal Atlanta error.
Some day there might be a global land temperature compilation that does not use urban areas.
I’ve proposed island lighthouses be used as they will be free of most local anthropogenic effects.
Otherwise, I commented at WUWT that the rise in urban temperatures from the mid-1970s is a direct result of introducing catalytic converters and other vehicle emissions reductions.
It is the Weekend Effect (more sunshine on the weekend due to fewer cars on the road) spread over several decades.