Update: John Holdren, the chief scientific adviser to Barack Obama, has said drastic measures to tackle climate change using massive technological measures should be considered. Holdren’s statement is a “personal opinion”, he says, but this is the strongest statement yet from within the Obama administration that geoengineering is being taken seriously. As we reported earlier in the year, the proposal has now moved into mainstream scientific and political thought.

IN A room in London late last year, a group of British politicians were grilling a selection of climate scientists on geoengineering – the notion that to save the planet …