As the carbon dioxide in the air hits 400 parts per million for the first time in human history, some are arguing that the best way address climate change is to use the controversial practice of geoengineering — the deliberate altering of the Earth’s ecological and climate systems to counter the effects of global warming. Supporters of geoengineering endorse radical ways to manipulate the planet, including creating artificial volcanoes to pollute the atmosphere with sulfur particles. Many scientists and environmentalists have raised concerns about geoengineering technologies designed to intervene in the functioning of the Earth system as a whole. We’re joined now by Clive Hamilton, professor of public ethics at Charles Sturt University in Canberra, Australia. Hamilton’s new book, “Earthmasters: The Dawn of the Age of Climate Engineering,” lays out the arguments for and against climate engineering, and reveals the vested interests behind it linking researchers, venture capitalists and corporations.