New York Times: Top U.N. climate change official Yvo de Boer told The Associated Press Thursday that he was resigning after nearly four years, a period when governments struggled without success to agree on a new global warming deal. His departure takes effect July 1, five months before 193 nations are due to reconvene in Mexico for another attempt to reach a binding worldwide accord on controlling greenhouse gases. De Boer is known to be deeply disappointed with outcome of the last summit in …