In a surprise announcement last evening from Beijing, President Obama and Chinese President Xi Jinping committed to ambitious cuts in carbon emissions over the next 15 years with the hope of preventing catastrophic global warming. The joint announcement calls for the United States, by 2025, to reduce carbon emissions by 26-28 percent below 2005 levels and for China to reduce net carbon emissions starting in 2030 or earlier and to increase the overall share of non-fossil fuels in primary energy consumption to around 20 percent by 2030. The announcement lays the groundwork for a global agreement to reduce carbon emissions at the United Nations Climate Conference in Paris in December 2015.