Scientific American: Emissions of a greenhouse gas that has 17,000 times the planet-warming capacity of carbon dioxide are at least four times higher than had been previously estimated. Nitrogen trifluoride (NF3) is used mainly by the semiconductor industry to clean the chambers in which silicon chips are made. The industry had in the past estimated that most of the gas was expended during the cleaning process and only about 2 percent escaped into the air. But the first-ever measurements of nitrogen trifluoride …