Danger Dust

From dumping iron into the ocean to launching mirrors into space, proposals to cool the planet through “geoengineering” tend to be controversial—and sometimes fantastical. A new idea isn’t any less far-out, but it may avoid some of the usual pitfalls of strategies to fill the atmosphere with tiny, reflective particles.

In a modeling study published this month in Geophysical Research Letters, scientists report that shooting 5 million tons of diamond dust into the stratosphere each year could cool the planet by 1.6ºC—enough to stave off the worst consequences of global warming. The scheme wouldn’t be cheap, however: experts estimate it would cost nearly $200 trillion over the remainder of this century—far more than traditional proposals to use sulfur particles.