The Pope is a very influential person in the world. He is the head of the Catholic Church which has millions of followers and he guides the direction the Church as a whole takes. This commands a lot of influence and by making a decree to "save the planet from debris, desolation and filth" will have a great impact on his millions of followers.
With 1.2 billion Roman Catholics worldwide, the Pope's opinions have great influence. When he urges Christians to save the planet, efforts to combat pollution are bolstered and individuals can be motivated to do their part. Increasing numbers of American Catholics are leaving the Republican Party in the 2016 election cycle, reflecting a poll by the Pew Research Center that reported 70 percent of American Catholics supporting the Pope's views.
No the Pope does not have influence over all of the world's people. Though his message is a positive one it is completely reasonable to say that the Pope has influence over only those that subscribe to the beliefs of his church and religious sect. It is very unlikely that the Pope will have influence over non religious people as well as those who adhere to and celebrate a different faith such as Islam or Judaism.
The Pope does not have worldwide influence. In fact, the vast majority of the world is not Catholic, nor do they really care what the Pope thinks. Many in the media give this Pope more coverage, because a lot of journalist tend to agree with his views on social justice. This does not mean that everyone else in the world agrees with the Pope though.