USA Today: In three reports on global warming, the U.S. National Academy of Sciences Wednesday called for limiting greenhouse gas emissions by setting a price on them. The three “America’s Climate Choices” reports, requested by Congress under the Bush administration, come as roiling debate over climate and energy legislation in Washington and the ongoing oil spill in the Gulf of Mexico cloud future energy decisions. Echoing past reports such as the 2007 Intergovernmental Panel on Climate …