Bloomberg: The discount on United Nations greenhouse gas credits compared with European Union allowances shrank to its narrowest level in more than three months as regulators consider a review of hydrofluorocarbon-23 projects. The UN discount against 2010 EU permits fell 11 percent to 1.87 euros ($2.41) a metric ton, the lowest since April 30, according to the spread contract traded on the European Climate Exchange in London as of 12:31 p.m. local time. “There has been a request for …