Alan Robock. “20 reasons why geoengineering may be a bad idea”. Bulletin of the Atomic Scientist. 2008: 14. Cost. Advocates casually claim that it would not be too expensive to implement geoengineering solutions, but there have been no definitive cost studies, and estimates of large-scale government projects are almost always too low. (Boston’s “Big Dig” to reroute an interstate highway under the coastal city, one of humankind’s greatest engineering feats, is only one example that was years overdue and billions over budget.) Angel estimates that his scheme to launch reflective disks into orbit would cost “a few trillion dollars.” British economist Nicholas Stern’s calculation of the cost of climate change as a percentage of global GDP (roughly $9 trillion) is in the same ballpark; Angel’s estimate is also orders of magnitude greater than current global investment in renewable energy technology. Wouldn’t it be a safer and wiser investment for society to instead put that money in solar power, wind power, energy efficiency, and carbon sequestration?