“Turning tar sands into oil and burning it as fuel produce enormous amounts of carbon dioxide.
To prevent an average global temperature increase of more than two degrees Celsius, triggering potentially catastrophic climate change. cumulative carbon emissions must be kept below one trillion metric tons.
The earth’s atmosphere is already more than halfway to the trillion-metric-ton target; expanding production of even more tar sands would accelerate emissions.
If built, the Keystone XL pipeline will be a spigot that speeds up tar sand production, pushing the planet toward its emissions limit.”
Greenhouse Goo – Scientific American, July 2013