Trees

 There are various cities in Germany that you can travel into (urbanized types) that have a abnormal amount of tree landscaping/cover.  I came to realize this point about 20 years ago....that things just seem cooler inside of these cities...than a mile or two outside of them.

12 C (53 F) difference?  Well....I'd question that part of the analysis.  Just in Wiesbaden....if you hang around the train-station (concrete-magnet for heat) and a mile away in the city park....I'd say there are 3 degrees of difference.

But getting people hyped up to plant more trees?  You will end up with half the population fully in favor, and half being anti-tree.