An essay on the subject by Mark Jaccard of Simon Fraser University on Policy Options:
When asked which climate policy in Canada reduced the most CO2 emissions over the last decade, many people guess BC’s well-publicized carbon tax. They’re wrong. It was Ontario’s ban on coal-fired power, which reduced annual emissions by 25 megatonnes (MT). Surely, then, BC’s carbon tax must have caused the most reductions in that province. Wrong again. The 2007 “clean electricity” regulation forced BC Hydro to cancel two private coal plants and its own gas plant. This cut BC’s projected annual emissions in 2020 by 12 to 18 MT. The carbon tax is slated to reduce 2020 annual emissions by 3 to 5 MT.
It’s the same in any jurisdiction that has significantly reduced emissions. Experts show that the carbon pricing policy in California, which Quebec has now joined, will have almost no effect by 2020. Ninety percent of that state’s current and projected reductions are attributed to innovative, flexible regulations on electricity, fuels, vehicles, buildings, appliances, equipment and land use. Even Scandinavian countries, famous for two decades of carbon taxes, mostly used regulations to reduce emissions. For example, the greatest CO2 reductions in Sweden happened when publicly owned district heat providers were forced to switch fuels.