Agence France-Presse: Rich and poor nations squabbled here on Sunday over the controversial Copenhagen climate accord amid warnings the battered UN system could not afford another failure in its quest to tackle global warming. As countries struggled to rebuild trust after the stormy summit in Copenhagen last December, UN climate pointman Yvo de Boer said the key to the worldwide process lay with a November 29-December 10 meeting in Cancun, Mexico. Cancun had to yield a “functioning architecture” on …