I believe that we must take a proactive approach to climate change. However, the Canadian economy is important for the prosperity of Canada and I believe the transition to a fully renewable energy reliant system should be a progressive process. Until then, oil should continue to be exported.
To help transition the oil industry to being more-green, companies could begin to use electrical equipment and machinery. It seems wasteful to use fossil fuel powered machinery to extract fossil fuels. There is no logic in using 3 barrels of oil to extract 5. Of course, transitioning would take time and the right kind of technology needs to emerge. In addition, we still need coal to make products like steel and oil based lubricants are a necessary component for any machinery.
The demand for oil is increasing and it is not tied to the Canadian oil market. If countries can't get the oil they need from Canada, they will get it elsewhere - potentially from countries that are not as environmentally conscious.
In any case, as the demand for oil decreases and Canada transitions to more environmentally friendly energy sources, the oil industry will correct itself and scale down operations accordingly as per free market forces. If oil is to be transported, it must be done in a manner in which there is as little risk to the environment as possible.