Bloomberg: United Nations carbon offsets rose the most in 17 months after regulators said they are reviewing projects that cut hydrofluorocarbons, fueling speculation that the supply of credits will plunge. UN Certified Emission Reductions for December 2010 gained as much as 5.8 percent, the most since March 9, 2009, to 13.29 euros a metric ton in London. CERs, awarded to projects that lower emissions in developing nations, can be used to comply with the European Union’s emissions trading …