Not on a matter of science. If the Pope thinks that there is GW, that is his belief based on the scientific facts that he has seen. Others may come to different conclusions based on their own research. The infallibility of the Pope, bishops, and Church only applies to faith and morals. The Church leaves scientific research up to the scientists of the world. There have been convincing studies on both sides of the GW argument. To my knowledge, the only binding belief that could come from the Pope is if he made a Church Law that the members of the Church should do whatever they can, within their power, to combat harming the environment, and to promote greener living. The Pope cannot say that we must believe GW is true.