There are a couple of news reports out about a new Hadley study on the synergistic effects of greenhouse warming and the urban heat island.

The urban heat island effect, often used by skeptics to discount global warming data, is the very real effect in which all that pavement, buildings and other thermal mass that we've built up in cities makes them warmer places. While the deniers' attempts to use the UHIE to explain away warming is pretty clearly bunk - serious climate scientists have gone to to a great deal of effort to factor the effect into their data analysis - the effect is nontheless real.

The new Hadley study, according to the news accounts, seems to be pointing out the somewhat obvious point that for the folks living in cities, the greenhouse gases' enhanced heat trapping means more of that urban heat will be held in overnight, which means warmer overnight temperatures.

I haven't been able to find the study itself - if anyone's seen it, I'd appreciate a citation.