“Black carbon," the product of incomplete combustion of everything from wood to diesel fuel, isn’t just something you put on Mary Poppins chimney sweeps to make them look picturesque. It also contributes to climate change, and it will turn your lungs into something from an anti-smoking PSA faster than you can ask for just one more spoonful of sugar. The flip side is that we could save a lot of lives with just a little cleanup.

A new study by the Stockholm Environment Institute finds that reducing black carbon could save two and a half million lives a year. And while we’re doing that, we could save more lives in the future, because the stuff is also an agent for global warming: As it lingers in the atmosphere, it makes the earth darker, thus making it absorb more energy from the sun. The study found that even though black carbon doesn’t stick around for ages like CO2, cutting it could help preserve glaciers and reduce warming in the Arctic by two-thirds.

Fortunately, there are simple, relatively inexpensive solutions — better wood-burning cookstoves (which can be had for just a few dollars), cleaner-burning two-stroke engines in the world's countless small motorized vehicles, and the like.

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