David Keith is Gordon McKay Professor of Applied Physics and Professor of Public Policy at Harvard University. He is also executive chairman of Carbon Engineering.  Because he’s a well-known expert in the largely theoretical field of geoengineering (deliberately modifying the Earth’s climate) he has become an often demonized target for conspiracy theorists who think that the climate is actually being secretly modified using “chemtrails.” We discuss the actual state of Geoengineering research (just starting to do very small scale tests), the plausibility of doing it secretly (almost none), and Professor Keith’s experiences with the chemtrail theorists over the last decade.   Links: * The Keith Group at Harvard University * Carbon Engineering