In the sense it is used now it's not even a theory, according to the scientific process. A century of recorded temperatures and weather pattens applied to a 3.4 billion year old planet is nothing.
Climate change, in the apolitical sense, is a true statement. Entropy demands systematic changes in stellar bodies like planets, and their climates will be affected. This is to say, for example, the Earth has not always been the way it is now. It was, at one time, a ball of molten lava. It has cooled much since and the climate is very different. Our industrialized period of carbon emission is about 1/34000000 is 2.94x10^-8% of our history.