I was also very surprised that the author didn't mention the urban heat island effect. While some of the temperature increase can be attributed to global warming, some of it might also be showing that Bostan has become more urbanized since 1890.
True. To people living in Boston, that still implies the climate has changed, though. It just means it's a stretch to infer anything about the world from it (not that this would be a good idea even in the absence of the heat island effect.)
