For two decades, the world’s governments have failed to meet their own commitment to reduce emissions of carbon dioxide, the main heat-trapping gas. As frustration builds among scientists, some of them have begun to argue for research on a potential last-ditch option in case global warming starts to get out of control. It is called geoengineering — or directly manipulating the Earth’s climate.

The idea sounds like science fiction, but it is not.

Citizens of developed economies are used to being shielded from the environmental or human impacts of the products and services they use every day.