John Abraham has an article on the Keystone Pipeline decision at the Guardian. The post really has two parts, the first describes the scientific case about why mining the Alberta tar sands is a very bad thing
Tar-sand oil is very hard to remove from the ground; it requires enormous amounts of water and energy just to get it to the surface. As a result, it releases more greenhouse gases than conventional fossil fuels. It really is the dirtiest of the dirty. Approval of the Keystone pipeline will lock us in to decades of dependency on this dirty energy at a time when we need to develop clean sources of energy.
But do the tar sands really matter that much? The answer is clearly yes. Alberta has 1.8tn barrels of oil contained within the tar sands. Extracting and burning all of that tar will cause a global temperature increase of about 0.4oC (0.7oF). That is about half of the warming that humans have already caused. For perspective, according to a recent study, the amount of oil-in-place in the Alberta tar sands is approximately seven times that of Saudi Arabia's proven reserves.
But wait, it gets worse. One of the byproducts of tar-sand extraction is a substance that is like coal ... only dirtier. That byproduct, petroleum coke (affectionately called Petcoke), emits more carbon dioxide than even coal.The second is a political statement, that this decision is a marker for the Obama administration which will determine the amount of support that it gets going forward on environmental and related issues. Rather than quoting John on this, Eli would point to a comment elsewhere by Leopold Basement