Book excerpt: Geoengineering is the deliberate and large-scale intervention in the Earth's climate system in an attempt to mitigate the adverse effects of global warming. Now that a climate emergency is upon us, claims that geoengineering is inevitable are rapidly proliferating. How did we get into this? What options make it onto the table? Which are left out? Whom does geoengineering serve? These are some of the questions that the thinkers contributing to this volume are exploring.