Edward Glaeser argues in this excellent article in City Journal that one of the best ways (if not the best) to fight global warming is to build denser, more compact, more transit friendly cities.
Of course, he doesn´t stop just there. A city like San Francisco is more efficient like New York, for instance, mainly because heating costs are lower but also because they get their electricity from more efficient energy sources. Houston is blessed with a warm climate, but its inhabitants waste a lot of carbon by driving around and powering their air conditioning with dirty power generation.
The real key, however, is not the efficiency of the metro area as a whole, but how much more efficient some city cores are compared to the suburbs. New York City is, in this case, the poster child of earth-friendliness.
Connecticut has very ambitious greenhouse gas emision targets on the books. It will be a good idea to take these ideas seriously when devising policy, as some of the bills bellow do.