Think of heat as like nature's income tax, every energy transaction you do is subject to a heat tax. Eventually almost all energy is converted into heat. Even t

Think of heat as like nature's income tax, every energy transaction you do is subject to a heat tax. Eventually almost all energy is converted into heat. Even the sun converts every chemical into its lowest energy state and releases all that energy in the atoms as heat. The primary thing the universe currently does is turn matter into heat, and tries to distribute that heat evenly. Eventually most of the energy for earth either becomes heat in the earth, gets radiated into space, or slows the earths rotation around the sun, or spin. Of all of these things the dominant two are heat radiating into space (this is by far the largest), and heating the earth, with a few things like the tides slowing the rotation of the earth. A little bit of it gets stored as chemical energy through plants and animals, but eventually those get burned either through fire, or chemical decomposition. To give you an idea of how much heat escapes, if the sun stopped, and we used our nuclear arsenal to replace it, we'd have about 30 minutes of sunlight. The idea that AC causes heat in cities to any real extent is laughable, if AC was capable of changing the temperature of the earth to any meaningful degree we'd just water cool the heat exchanger and solve global warming by dumping the heat into the ocean.