You misunderstood the mechanism of global warming. The problem of CO2 is that it lingers in the atmosphere and acts as a blanket to keep the earth warm. So, i

You misunderstood the mechanism of global warming. The problem of CO2 is that it lingers in the atmosphere and acts as a blanket to keep the earth warm. So, if you make 1 kWh of energy by burning fossil fuel, the resulting CO2 ends up warming the earth by much more... (probably several thousands kWh, though I'm too lazy to look it up now.) Compared to that, whatever waste heat emitted by a nuclear plant is a drop in the bucket.