Reuters: Rich nations must spell out their plans for cutting greenhouse gases more clearly to enable U.N. talks in Mexico to agree the cornerstone of a pact to slow global warming, the U.N.’s climate chief said. Christiana Figueres said the annual November 29-December 10 meeting in Mexico would fall short of a U.N. treaty to combat climate change, saying countries learnt there was no “magic bullet” for a quick new U.N. accord at a Copenhagen summit last year. She urged rich nations to …