When air pollution hurts people’s health and heats up the climate it makes sense to do something about it. But what about pollution that cools the planet?
AN IDEAL fossil-fuel power-plant would produce power, carbon dioxide and nothing more. Less-than-ideal ones—not to mention other devices for the combustion of carbon, from diesel generators to brick kilns and stoves burning dung—also emit various gases and gunk. These often cause local environmental problems, damaging lungs, hurting crops and shortening lives. And some of the gunk, notably soot or “black carbon”, can warm the planet, too.
Next week ministers attending the governing council of the United Nations Environment Programme (UNEP) in Nairobi will be presented with the summary of a new report on how fighting air pollution can help the global climate (the report itself is due to follow a couple of months later). The summary makes a powerful case for acting on two short-lived climate “forcings”, factors that change the amount of energy the atmosphere absorbs, as carbon dioxide does, but stay in it only briefly. One is black carbon and the other is ozone, which is vital for blocking ultraviolet rays in the stratosphere but hazardous in the bits of the atmosphere where plants live and people have to breathe. …
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