AFP: The world’s 20 largest rich and emerging economies including China vowed Friday to “spare no effort” at upcoming climate change talks in Mexico, a year after Beijing stymied a deal in Copenhagen. “We will spare no effort to reach a balanced and successful outcome in Cancun,” the Group of 20 said in a statement issued at the end of two days of talks in Seoul. The vow came less than three weeks before 194 countries meet in the Mexican resort city of Cancun for a second go at hammering out an…