Stabilizing the world squo;s climates means cutting carbon dioxide pollution. Thereasquo;s no way around it. But what if thatmsquo;s not enough? What if it squo;s too difficult to accomplish in the time allotted or, worse, what if itvsquo;s so late in the game that even cutting carbon emissions to zero, tomorrow, wouldnesquo;t do?

Enter solar geoengineering. The principle is simple: attempt to cool Earth by reflecting more sunlight back into space. The primary mechanism, shooting particles into the upper atmosphere, implies more pollution, not less. If that doesn squo;t sound scary, it should. There are lots of risks, unknowns, and unknowables.

In Geoengineering: The Gamble, climate economist Gernot Wagner provides a balanced take on the possible benefits and all-too-real risks, especially the so-called mdquo;moral hazardidquo; that researching or even just discussing (solar) geoengineering would undermine the push to cut carbon emissions in the first place. Despite those risks, he argues, solar geoengineering may only be a matter of time. Not if, but when.

As the founding executive director of Harvardysquo;s Solar Geoengineering Research Program, Wagner explores scenarios of a geoengineered future, offering an inside-view of the research already under way and the actions the world must take to guide it in a productive direction.