The cities might be getting hotter because they are packed cheek to jowl with third world mud people. But the rest of the world is unchanged. Completely unchanged.
The Arbor Day Foundation recently published a paper saying that a lush tree canopy can make a city 10 degrees cooler. So, that means cutting down trees and building asphalt parking lots can make a city 10 degrees warmer. So, using temperature changes in cities to calculate warming is not even valid.