The oil-producing region of North Dakota and Montana leaks 275,000 tons of methane annually, a significant amount of the greenhouse gas but less than previously believed, a study released Wednesday said. Associated Press. May 12 2016 http://bigstory.ap.org/article/c4ad89016cbd4968bcd58b00b8d76191/study-bakken-oil-field-leaks-275000-tons-methane-yearly