One way to think about the keystone project--the 2,000-mile (3,220 km) pipeline that would bring oil from the tar sands of Canada to the Gulf of Mexico--is to ask what would happen if it is never built. The U.S. Department of State released an extremely thorough report that tries to answer this question. It concludes, basically, that the oil derived from Canadian tar sands will be developed at about the same pace whether or not there is a pipeline to the U.S. In other words, stopping Keystone might make us feel good, but it wouldn't really do anything about climate change.
Given the need for oil in the U.S., Canadian producers would still get Alberta's oil to the refineries on the Gulf of Mexico. There are other pipeline possibilities, but the most likely method of transfer is by train. The report estimates that it would take daily runs of 15 trains with about 100 tank cars each to carry the amount planned by TransCanada. That would be a large increase in traffic from what now goes north to south, but it would hardly be an insurmountable problem. Rail traffic in this corridor is already exploding: the number of carloads of crude oil doubled from 2010 to 2011, then tripled from 2011 to 2012. And remember, moving oil by train produces much higher emissions of CO[subscript 2] (from diesel locomotives) than flowing it through a pipeline.
Canada could also transport the oil by train or pipeline west to British Columbia and then on to Asia, where demand is booming. Right now that seems a distant and costly prospect, but having visited Alberta recently, I can attest that Canadian businesspeople and officials are planning seriously for Asian markets--especially since they have come to regard U.S. energy policy as politicized, hostile and mercurial. Whoever uses the oil, the CO[subscript 2] will be released into the atmosphere just the same.
Also, if we don't use oil from Alberta, we will need to get it somewhere to fuel our transportation needs--from Venezuela, Mexico, Saudi Arabia or California. Some of these oils are heavy crude, and processing, refining and burning them is believed to be even more harmful to the environment than using fuels from refracted Canadian oil sands. Switching from oil sands to, say, Venezuelan crude (the most likely alternative) would reduce greenhouse-gas emissions by a minimal amount or not at all. To the extent that this would make us use more coal for electricity generation, it would be a big step backward for the environment. For many of these reasons, the scientific journal Nature, long a leader on climate change, argued in an editorial that President Obama should approve Keystone. A decision is expected this spring.