Oil and gas operators in Texas and a dozen other U.S. states have flared, or burned off, at least 3.5 trillion cubic feet of natural gas over much of the last decade, according to an analysis of satellite data by the Howard Center for Investigative Journalism. The industry has also directly released, or vented, into the atmosphere unknown amounts of the methane-rich gas. Flaring and venting release a cocktail of carbon dioxide, methane and other pollutants. But regulators are unaware of the total volumes of greenhouse gases being released, even as climate scientists warn that without steep, immediate reductions, the world will miss its chance to avert the deadliest and most destructive effects of climate change.