Tar sands exploitation would mean game over for climate, warns leading scientist. The Guardian 20130519

http://www.guardian.co.uk/environment/2013/may/19/tar-sands-exploitation-climate-scientist

Canada's tar sands are the third biggest oil reserve in the world, but separating the oil from the rock is energy intensive and causes three to four times more carbon emissions per barrel than conventional oil. Hansen argues that it would be "game over" for the climate if tar sands were fully exploited, given that existing conventional oil and gas is certain to be burned.
"To leave our children with a manageable situation, we need to leave the unconventional fuel in the ground," he said. Canada's ministers were "acting as salesmen for those people who will gain from the profits of that industry," he said. "But I don't think they are looking after the rights and wellbeing of the population as a whole.