Scientific American: In a draft assessment of the proposed Keystone XL pipeline, consultants for the U.S. State Department judged that building it would have no significant impact on greenhouse gas emissions. Why? Because the analysts assumed the tar sands oil would find a way out with or without the new pipeline. The U.S. Environmental Protection Agency does not agree. Keystone XL's ability to carry an additional 830,000 barrels of tar sands oil per day is vital to expanded production of the tarry crude in Alberta....