And we're supposed to be looking for alternative energy sources as well?
Well, wonder no more, I found a solution to both of problems at once:
Why don't we just built a very very very huge solar pad over the oceans? This way, the amount of sunshine obsorbed by the water reduces and therefore the water doesn't heat up too much (yay, save the polar ice caps) and also we get a shitload of produced electricity that we can use to execute our prisoners.
Alternatively, you can just leave the fridge door open at night, cooling down the planet.