CO2 concentrations have been far higher in the past and the world survived. Nor is it the most potent greenhouse gas...methane is far more potent, yet never discussed. Perhaps that's because it's politically incorrect to look at the impact of agriculture...rice paddies in particular.
Ecotards keep ignoring the elephant in the room...human overpopulation. Population growth in the third world is ripping out the planet's lungs.
The amount of CO2 produced by the oilsands is utterly irrelevant when compared to the carbon sink that's been destroyed in the Amazon and Malaysian rain-forests.
And again...every barrel of oil that we don't produce will be replaced by somebody else, with lower environmental standards