"Energy-related carbon dioxide emissions in the United States from January through March were the lowest of any recorded for the first quarter of the year since 1992, the federal Energy Information Administration reports. The agency attributed the decline to a combination of three factors: a mild winter, reduced demand for gasoline and, most significantly, a drop in coal-fired electricity generation because of historically low natural gas prices. Whether emissions will continue to drop or begin to rise again, however, remains to be seen, experts said Friday. “While this is a positive step, we shouldn’t just say, ‘Oh, we’ve got plenty of natural gas, we can just switch to that, problem solved,’ and move on,” said Jay Apt, the director of the Carnegie Mellon Electricity Industry Center, who was not involved in compiling the study. Carbon dioxide emissions from energy consumption totaled 1.34 billion million metric tons in the first quarter, down nearly 8 percent from a year earlier, the Energy Information Administration said.