Associated Press: President Barack Obama declared Friday a "meaningful and unprecedented breakthrough" had been reached among the U.S., China and three other countries on a global effort to curb climate change but said much work was still be needed to reach a legally binding treaty. "It is going to be very hard, and it’s going to take some time," he said near the conclusion of a 193-nation global warming summit. "We have come a long way, but we have much further to go." The president said there …