"I think the biggest threat to the world is high energy costs. And if you believe in global warming, then you believe the biggest threat to the world is too much use of dirty energy. So I think for both those reasons, as nations, we've just got to work much faster at becoming self-sufficient in clean energy.
"Set a target in America and Britain, by 2020, that we don't import any more oil -- we power our planes on clean fuels, we power our cars on clean fuels, and we make sure that our buildings are insulated and powered on clean fuels. With an absolute determination, we can get there. Being reliant on sending out billions and billions overseas seems foolish."