
Tomorrow’s world
Rolling the dice to save the planet
You may not have heard, says Bill McKibben in The New Yorker, but scientists already know how to reverse global warming. It’s called solar geoengineering, and basically involves spraying particles of some “highly reflective” material – probably sulphur dioxide – into the stratosphere to deflect sunlight. This already happens naturally with big volcanoes: an eruption like that of Mt Pinatubo in the Philippines in 1991 can “measurably cool the world for a year or two”. And it’s cheap – climate boffins reckon it would cost only a few billion dollars a year. The thing is, everyone who studies this technique “seems to agree that it’s a terrible thing”. Because the question isn’t whether solar geoengineering can work. It’s: “What else would it do?”