If there is one scientist more responsible than any other for the alarm over global warming it is Dr Hansen, who set the whole scare in train back in 1988 with his testimony to a US Senate committee chaired by Al Gore. Again and again, Dr Hansen has been to the fore in making extreme claims over the dangers of climate change. (He was recently in the news here for supporting the Greenpeace activists acquitted of criminally damaging a coal-fired power station in Kent, on the grounds that the harm done to the planet by a new power station would far outweigh any damage they had done themselves.)