Global warming is not caused by waste heat. It is not caused by energy use per-se (indeed, energy is never used, but always conserved). It is caused by a shift

Global warming is not caused by waste heat. It is not caused by energy use per-se (indeed, energy is never used, but always conserved). It is caused by a shift in the equilibrium temperature, at which the amount of energy radiated by the Earth equals the amount of incident sunlight. The surface of the Earth gets hotter to radiate the same amount of energy (picture an incandescent light bulb), because greenhouse gasses form an insulative barrier. Burning fossil fuels releases CO2, which increases the amount of insulation. It does also release heat, but that hardly matters; if that were all it did, the heat would ultimately be radiated into space as infrared. The problem isn't "energy use". Nuclear, for example, wouldn't appreciably increase planetary temperatures (I say this not to be a booster for nuclear power, but just because it adds heat that does not come from the sun without creating greenhouse gasses, so it works as an example.). The problem is greenhouse gasses. Toy ODE model: dx/dt = -k x + a + b. Here, x is temperature, a is solar heat input, and b is heat input from human sources. I'm dropping some coefficients that would make the units strictly work. We have a >>> b. The coefficient k says how easily the Earth radiates heat. Adding greenhouse gasses makes k closer to zero. At equilibrium, dx/dt = 0. Solving, x = (a + b) / k ~= a / k Again, b is tiny relative to a. So almost the only thing that matters is k.