Isn the apparent warming due to urbanisation?
No. The below image shows the results of a recent analysis at the Hadley Centre of temperature trends over the last 50 years deduced separately from measurements on the most windy nights and the least windy nights, from the same stations. If urbanisation were causing the observed warming, one would expect calmer nights to have warmed more, as it is in these conditions that the heat island effect would act to warm the station compared to its rural surroundings. In fact, the results showed no difference between trends on windier and calmer nights, confirming that urbanisation is not to blame.
