Guardian: It’s an exceptionally inconvenient truth. Only one American in three believes that human beings are responsible for climate change: a polling result 10% down on where opinion rested the year before. Worse, the number of Americans who believe that climate change is a hoax or a scientific conspiracy – not doubting, just damned blank certain – has doubled since 2008. Add in those who assert that the changes, if any, are of “no significant concern”, and you’ve got 30% of the US denying, scoffing …