Guardian: Barack Obama is poised to arrive in Copenhagen tomorrow with additional pledges of cash for poor countries which will suffer the most from global warming, a day after America’s promise to support a $100bn a year climate fund. Obama’s arrival has been the most anticipated event of the 10-day summit, which has lurched between optimism and rank despair. He will seek to make a decisive impact, building on the announcement today by Hillary Clinton, the secretary of state, who said for the …