Scientific American: International expectations are high for President Obama and Congress to bring a strong U.S. negotiating position to the U.N. climate talks in Copenhagen this December. But there are big questions about how much U.S. leaders might be able to deliver. “I think neither the calendar nor the economy is our friend right now,” Carlos Pascual, vice president and director of foreign policy at the Brookings Institution, said today during a Washington panel on the Copenhagen …