The most common argument for the use of nuclear power over power from conventional fossil fuels is the diminished environmental impact that nuclear power promises. While nuclear fission reactions do not directly produce greenhouse gases like fossil fuel combustion, power plants affect the environment in a myriad of ways. In order to elucidate a clearer environmental impact comparison between all power generation methods, including renewables, less obvious environmental effects must be adequately assessed. For example, both nuclear and fossil fuel plants produce significant thermal pollution to bodies of water. Thermal water pollution is the degradation of water quality due to a change in ambient water temperature.