So greenhouse gasses (CO2, etc) are today considered to be major causes of global warming. These are largely attributed to consumption of non renewable energy sources.
At least use of renewable energy such as wind power, is simply converting one energy source to another and not adding to the overall bill to the planet.
Nuclear Energy (aside from the waste storage issue) may have a low CO2 input, however it is still creating energy from a non renewable source. Perhaps more importantly the nuclear reaction isn't something that would normally occur in vast quantities. Thus use of nuclear energy is creating a vast extra input of energy to the planet that is not natural. That still has to go somewhere so why won't it too contribute to global warming
