BBC: Economist Lord Stern has said he is optimistic that a global deal to reduce carbon dioxide emissions will be struck under the US presidency of Barak Obama. Lord Stern, who was behind the first detailed economic assessment of the impact of climate change, said US and Chinese agreement to a cut was crucial. President George W Bush’s climate views were “prehistoric” and had been seen as an obstacle, Lord Stern told the BBC. But many now believed the new president could take …