Theorizer (that's a real word?!) Teddy brings up an objection in the comments to part 1:
"Highly urbanized countries are the most developed countries, and the standard of living is higher. Higher standard of living means more emissions from transportation and manufacturing."
Wikipedia defines standard of living by the human development index, so I'll use that too. (The data is from 2005, while the other two measures are from 2007, but there shouldn't have been too much change in HDI since then.)
There isn't much of a relationship between this HDI index and carbon dioxide emissions (although it is positive, r square = 0.047), and there isn't much of a relationship between standard of living and percentage of urban population in the first place:
Granted, there aren't many countries that even report carbon dioxide emissions, and those countries tend to have higher standards of living . Maybe a better idea would be to do an analysis by US state, which would probably have more data.
By the way, the country with the highest carbon dioxide emissions per capita? Luxembourg, whose slogan is, "come visit our country, but make sure you also have an afternoon activity." Ouch.