New York Times: Yvo de Boer, the stolid Dutch bureaucrat who led the international climate change negotiations over four tumultuous years, is resigning his post as of July 1, the United Nations said on Thursday. In a statement announcing his departure, Mr. de Boer expressed disappointment that the December climate change conference of nearly 200 nations in Copenhagen had failed to produce an enforceable agreement to reduce emissions of greenhouse gases that climate scientists say are contributing to …