Grist: If the Keystone XL pipeline is built, it could lead to up to four times as much CO2 pollution as the State Department has estimated, according to a new study. And the study wasnt written by activists. It was conducted by scientists at the Stockholm Environment Institute and published in the journal Nature Climate Change. Why are these new figures so much higher than previous ones? The Associated Press explains: The U.S. [State Department's] estimates didnt take into account that the added oil...