When Jeff Goodell first encountered the term "geoengineering," he had a vague sense that it involved outlandish schemes to counteract global warming. As a journalist, he was deeply skeptical. But he was also intrigued. The planet was in trouble. Could geoengineers help? Climate change may well be the biggest crisis humanity has ever faced. Temperatures in some regions of the world could increase by as much as fifteen degrees by the end of the century, causing rising sea levels and severe droughts. But change could also happen much more suddenly. What if we had a real climate emergency, the ecological equivalent of the subprime mortgage meltdown--how could we cool the planet in a hurry? As Goodell shows in this bracing book, even if we could muster the political will for it, cutting greenhouse gas emissions alone may not be enough to reduce the risk of climate catastrophe. This has led some scientists to pursue extreme solutions: huge contraptions that would suck CO2 from the air, machines that would brighten clouds and deflect sunlight away from the earth, even artificial volcanoes that would spray heat-reflecting particles into the atmosphere. In How to Cool the Planet, Goodell explores the scientific, political, financial, and moral aspects of geoengineering. How are we to change the temperature of whole regions if we can ́t even predict next week ́s weather? What if a wealthy entrepreneur shots particles into the stratosphere on his own? What about wars waged with climate