Taxes on CO2 emissions are the most economically efficient way to reduce emissions. This is because it allows for competition between different ways of reducing emissions and doesn't pick winners and losers like crony-capitalism does. Admittedly, they can lead to some emission spillovers to jurisdictions without taxation of CO2 emissions. That's why it would be optimal to have a global pigouvian tax on CO2 emissions, that applies to other countries. In the meantime, spillovers could be countered with either CO2 tariffs on imports or CO2 emission taxes that only apply at the margin for sectors of the economy that are more at risk of relocating to other countries.
Alternatively, if the goal is to reduce global emissions rather than meet Stephen Harper's goal of 30% emission reductions by 2030, then beyond a minimal level of taxation of CO2 emissions in Canada, it could be more economically efficient to buy emission credits from other countries and pay other countries to reduce emissions. But then if the CPC disagrees with reducing domestic CO2 emissions as the goal, then why did Stephen Harper create that as the target? And why don't any of the candidates or MPs criticize the decision by Harper?
It's almost like the CPC doesn't actually care about climate change, but they will say whatever to be elected. So in 2010, they would gladly agree to a 30% CO2 emission reduction target in 2030, because that is in the distant future and the Harper would be long out of power before he has to do anything to meet the target. Similarly, in 2020, all the MPs in candidates will agree to the net-zero CO2 emission target for 2050, because 2050 is in the distant future and they don't have to actually do anything today to meet that target. Even if they do win the next election, they will be long retired before 2050. Agreeing to a ridiculous target several decades in the future has the appeal that you don't have to do anything now, but you can pat yourself on the back at how green you are, and maybe get a few more votes. But it isn't good policy. The level of mitigation that society should do should be determined by weighting the various costs and benefits of different policy. Maybe that means more mitigation than the CPC wants today, but less mitigation than they promise in 2050.
But by opposing the most economically efficient way to reduce emissions (CO2 taxes) the CPC has no path forward to make a coherent and believable position on climate change. But I guess it is to be expected from an economically illiterate party that worships the Dairy Cartel.