Explain what kind of feedback is operating in this example: more and more people around the world are using more and more electricity, mostly made by more and more coal-fired electric power generation facilities burning more and more coal to run more and more air conditioners in larger and larger houses, causing more and more CO2 emissions which are trapping more and more heat in the atmosphere causing the Earth to get hotter and hotter, and more humid. How could we stop this feedback loop?