If all goes well, a balloon will soon rise from Esrange Space Center in Kiruna, Sweden. It will drift high into the upper atmosphere, where nothing will happen. The balloon will then return to Earth. Nevertheless, a collection of environmental groups—including the Swedish branches of Greenpeace and Friends of the Earth, and the Centre for International Environmental Law—is trying to stop it.

The campaigners are against the flight because of what comes next. The balloon is a test flight for something called the Stratospheric Controlled Perturbation Experiment, or SCoPEX, which is being run by Harvard University. The idea is that a future flight will release a small amount of calcium carbonate dust into the stratosphere, in order to help researchers learn more about solar geoengineering...

The Economist: Dusting the upper atmosphere could help counter climate change