页岩气燃烧时还会释放二氧化碳，尽管页岩气比煤炭的含碳量低一半，并且对美国将碳排放量减至20世纪90年代中期水平居功至伟。
And shale gas emits CO2 when burned, even though it has half the carbon content of coal and has played a significant role in cutting US carbon emissions to mid-1990’s levels.