Like coal, tar sands and oil shale are among the 'dirtiest' of fossil fuels--because they require hugely energy-intensive technologies to exploit them.
Extracting a barrel of petroleum from oil shale requires five times the energy needed to exploit a conventional petroleum deposit, and tar sands aren't much better.
For such reasons, former NASA climatologist Jim Hansen once described tar-sands as a "carbon bomb."
Canada is seen as the global leader of tar-sands exploitation, with the country trumpeting its expertise and multinational oil corporations and nations lining up to invest and send their experts there for training.
Globally, tar-sands deposits are massive, and they're increasingly being exploited. A new website shows tar-sands projects springing up across the globe, from Mongolia to the Congo, and Russia to Morocco. The U.S. alone is estimated to have up to a trillion barrels of recoverable petroleum in tar-sands deposits.
It's a frightening trend. With China building nearly one new coal-fired generating plant each week and Canada becoming a global cheerleader for some of the dirtiest carbon fuels, one has to wonder if the IPCC's sobering 'business-as-usual' scenario for carbon emissions might actually be too optimistic.