Heat is a one type of energy... Heat energy used lot in our life... Most of the time heat energy used to generate electric energy and other type of energies.... Heat energy liberates most the time to generate electric and other type of energies...
From the law of Einstein energy can't be generate either destroyed.. one type energy changed other type of energy.. here heat energy liberates when generate electric energy and other type... From that this liberated heat energy around the world so let we think the where.the heat energy gone...
I think it's to increase the world average temperature...