· Testimony to US Congress will also criticise lobbyists
· 'Revolutionary' policies needed to tackle crisis

James Hansen, one of the world's leading climate scientists, will today call for the chief executives of large fossil fuel companies to be put on trial for high crimes against humanity and nature, accusing them of actively spreading doubt about global warming in the same way that tobacco companies blurred the links between smoking and cancer.

Hansen will use the symbolically charged 20th anniversary of his