Half the lifetime pollution from a car happens during manufacture. Lets not buy more shit that does the same a-b.

Building the physical infrastructure for all those suburbians to live in the cities would also have a carbon impact.

In practical terms, in five years or so it's not going to be hard to get people to buy electric cars instead of gasoline, but it will still be practically impossible to get them to give up their houses, back yards, and cars to go live in the city.