More than half of the electricity generated in Alberta comes from coal. In the process of generating electricity, coal-fired power plants emit greenhouse gases (GHG) among other pollutants. Greenhouse gases are thought to be a large contributor to climate change. Coal plants emit about one tonne of carbon dioxide per MWh (1,000 kWh) of production. Conversely, gas-fired facilities produce from one-quarter to half a tonne per MWh.