Cities are responsible for the vast majority of the creation of the economy. They're also places into which we pour the vast majority of resources, the vast majority of energy and the places where a huge percentage of the decisions about how systems are built and how products designed, etc., happen.

Cabbies in particular seem to like discussing the fate the Earth.

Copenhagen has done a remarkable job creating streets that are focused on bicycles and pedestrians.

I think there's a gigantic generation gap in terms of how people understand the Internet and how much they think technology is an important factor in social change.

Urban retrofitting: creating different sorts of spaces and uses out of places that are already there.

You don't change the world by hiding in the woods, wearing a hair shirt, or buying indulgences in the form of 'Save the Earth' bumper stickers. You do it by articulating a vision for the future and pursuing it with all the ingenuity humanity can muster.

By fundamentally changing how we design the places and systems that enable our daily lives, we can slash emissions way beyond the immediate carbon savings - because our own personal emissions are just the tip of a vast iceberg of energy and resources consumed far from our view.