Reuters: President Barack Obama’s pessimism about passing U.S. climate legislation also dims chances for action to slow global warming both in U.N. talks and in other groups such as the G20, experts say. A lack of U.S. legislation to cut greenhouse gas emissions may also hit plans to raise a promised $100 billion a year by 2020 to help poor nations cope with climate change. That plan partly hinges on curbs on emissions to push up carbon prices. Obama conceded on Wednesday that big Republican gains in…