By Marc Gunther The risk of disruptive climate change grows every day. John Holdren, the White House science advisor, said last year that we have three options: Mitigate, adapt, suffer. If we don't mitigate (meaning reduce emissions), we'll have to adapt (move to new places, develop new crops, build sea walls). If we do neither, we'll suffer. But, as regular readers of this blog know, there' s a fourth option — geoengineering. Geoengineering is term used to describe planetary-scale technologies that are designed to counteract the climate effects of past greenhouse gas emissions to the atmosphere. I've been fascinated with geoengineering for about two years, and this week FORTUNE will publish my story, The Business of Cooling the Planet, about three startup companies that want to save the planet by capturing carbon dioxide from the air. This topic is so important that I'm planning to expand the story into a short e-book in the next couple of months. The FORTUNE story begins by describing how Microsoft founder Bill Gates became an expert on climate and energy: One of the cool things about being Bill Gates is that if you are curious about something, you can find smart people who will teach you whatever it is that you want to know. About five years ago, Gates decided that he wanted to learn about climate change, so he arranged for two of the world's leading climate scientists, David Keith of the University of Calgary in Alberta, Canada, and Ken Caldeira of the Carnegie Institution, to organize a series of seminars. Since then, Keith and Caldeira have recruited scientists, energy experts, economists, and policy wonks to deliver about a dozen detailed presentations to Gates. He prepares by doing hundreds of pages of reading, some quite technical; the ensuing discussions, which last three or four hours, can be intense. “Bill has the intellectual curiosity of a very bright graduate student,” Caldeira says, “but a graduate student whose time you are not supposed to waste.” This is no academic exercise. Gates has been convinced that the risk of global warming is worse than most people think. He can see that the world's governments have failed to curb the emissions caused by burning coal, oil, and natural gas. In June 2010 he put together a coalition of business leaders, including GE's Jeff Immelt, to urge Congress to invest more in clean-energy research, but that's not happening. So the Microsoft billionaire and philanthropist has stepped into the breach to become the world's leading funder of research into geoengineering — deliberate, large-scale interventions in the earth's climate system intended to prevent climate change and its repercussions. Since 2007, Gates has given about $4.6 million of his money to Caldeira and Keith for geoengineering research. Intellectual Ventures, a private company funded in part by Gates, has explored such technologies as building an 18-mile-long hose, tethered by balloons, that would spray tiny particles into the stratosphere to block the sun's rays. Gates has even attached his name to a patent application for ocean-churning technology designed to sap the strength of hurricanes, which appear to be getting fiercer because of global warming. The story goes on focus on three startup companies that are working on A straightforward, albeit audacious, way to cool an overheating planet: Build many thousands of big machines to remove carbon dioxide from the air. The companies are Carbon Engineering (in which Gates is an investor), Global Thermostat and Kilimanjaro Energy. They are all a long way from making any money from carbon dioxide removal, and indeed there are many skeptics who say the costs of pulling CO2 from the air are so high that it will never make business sense. Still, the work these companies are doing is important for three reasons, all of which underscore the way carbon dioxide removal (CDR) differs from solar radiation management, the better-known geoengineering technology: First, these companies are asking us to think about CO2 in a new way, not as a dangerous waste product or pollutant, but as a resource that can be captured, recycled and made into something new — potentially, carbon free fuels. Second, unlike some of the quicker, cheaper and easier forms of geoengineering (like shooting tiny particles into the stratosphere to block the sun), carbon dioxide removal is relatively low-risk. Yes, there are real issues about what to do with the CO2 once it's captured from the air, but those should be manageable. Third, while solar radiation management attempts to deal with the fact of climate change, i.e., a warming planet, carbon dioxide removal (CDR) goes right at the cause, by reversing the rising atmospheric concentrations of CO2. It's the closest thing we have to a time machine. None of this is to suggest that dealing with the climate crisis will be easy. It won't be, particularly given the dismal state of climate politics in the U.S. But that's another reason to hope that one or more of these startups find success. You can read the rest of the FORTUNE story here. Article courtesy of greenbiz.com