Well yes it puts CO2 in the air, but really everyone in Canada burning natural gas to stay warm is still like peeing in the ocean compared to the CO2 generated by China in a single day. Even if the man-made climate change myth had some validity to it, taxing natural gas just isn't going to do anything to stop it, and is just a revenue grab. So just say so.
Also - in terms of "alternate energies" - I support them, as long as people look at the entire picture. Some look at a wind turbine and say "see it doesn't generate any CO2". Well, that's not true. What about all of the CO2 generated in constructing it in the first place? And what about the acid boiling that is required for the giant rare earth magnet in each of those turbines? And what about all the birds that are blended by wind turbines? I'm not a big supporter of wind or solar. I do support nuclear though.