New studies show that perhaps it does make a difference where CO2 is emmited.

But a new study just published in Environmental Science and Technology by Stanford's Mark Jacobson adds a slight twist to this standard view. Older research has found that local "domes" of high CO2 levels can often form over cities. What Jacobson found was that these domes can have a serious local impact: Among other things, they worsen the effects of localized air pollutants like ozone and particulates, which cause respiratory diseases and the like. As a result, Jacobson estimates that local CO2 emissions cause anywhere from 300 to 1,000 premature deaths in the United States each year. And presumably the problem's much worse in developing countries.

http://www.grist.org/article/2010-03-17-if-it-does-matter-where-co2-is-released-cities-are-in-trouble