Climate Central: A temporary halt to the federal government's plan to cut electric power plant emissions has caused carbon prices in the Northeast's only cap-and-trade program to plummet, according to the U.S. Department of Energy. Carbon prices in the Regional Greenhouse Gas Initiative, or RGGI, have fallen 40 percent since the Supreme Court's decision in February to stay the Clean Power Plan -- from their peak at $7.50 per metric ton of carbon dioxide in December to $4.53 per ton in June. RGGI is America's first...