Cities may bear the brunt

Does it matter where carbon dioxide is emitted? No, will be the global chorus. Every tussle on the climate change front has been on the premise that emissions from any place will affect the world at large. 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 aggravate 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 well yes, the problem's much worse in developing countries where emissions are on the rise.

In the US, the new evidence adds another hurdle to the cap-and-trade plans by suggesting that it matters where pollution happens. Cap-and-trade rests on the assumption that a ton of carbon has the same impact regardless of where it’s emitted. If Jacobson’s study is strengthened, this could also pit cities against their rural parts.

Of course, one aspect of this is that governments may take their emissions a bit more seriously, but globally will this mean a brake to cooperation? Not necessarily, as this does not in any way negate the overall effect of carbon emissions, but merely tags on the local consequences.