Global warming or no global warming, it doesn't take an environmental engineer (or M.D. or rocket scientist or vegan or...) to figure out that the output of the internal combustion engine is baddd...cities with higher traffic have higher levels of respiratory disease, birth defects, foul-smelling air, etc.

Now...I'm not saying we should stop using the internal combustion engine. Far from it: I think many of the great advances we've made have come as a result of it. But we need to realize that our behavior comes at a cost. Strategy necessarily involves trade-offs. We should certainly consider whether it's more important to have an SUV for trudging around town, or to have grandkids with non-cancerous skin...