On his latest video for the Vlog Brothers, Hank Green spoke about the accidental experiment that cleaning up ship fuel has carried out on the climate, in a video titled "The Biggest Science Story of the Week". Among other things, Hank argues that this could be a crucial opportunity to learn about geoengineering. Geoengineering - according to this Vlog Brother - could be a "giant step forward". So what could geoengineering actually achieve to combat climate change? And why are many climate scientists far more skeptical than Hank lets on?