Does it matter where carbon-dioxide is emitted? From a climate perspective, at least, the standard answer has always been, "Not really." Carbon-dioxide mixes pretty evenly and uniformly throughout the atmosphere, so that the heat-trapping gases coming out of a factory in China have the same effect on global temperatures, pound for pound, as the greenhouse gases emitted by, say, cars in Delaware. (This is in contrast to a number of other air pollutants, whose effects are often localized—sulfur dioxide only causes acid rain in discrete areas.)
But a new study just published in Environmental Science and Technology by Stanford's Marc 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 cause serious health impacts in the area: 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.
