His encyclical on the environment called Praised Be: On the care of the common home was meant to be released this Thursday, however the Italian newspaper L'Espresso leaked the document.
The Vatican has denounced the leak as "heinous," but confirmed it would still be released as planned.
It's reported to say: "If the current trend continues this century we could witness climate change unlike anything seen before and the unprecedented destruction of ecosystems, with serious consequences for all of us.
"Climate change is a problem with serious implications for the global environment, social, economic, distribution [systems] and policies and constitutes one of the main challenges for humanity.
"The economic powers shall continue to justify the current world system, in which speculation and the aim for financial returns... ignore... the effects on the environment and on human dignity... environmental, human and ethical degradation are intimately connected.
"The warming caused by the enormous consumption of some rich countries has repercussions in the poorest places on Earth, especially in Africa, where the increase in temperature, combined with drought, has had disastrous effects on the performance of crops.
"Humanity is called to take note of the need for changes in lifestyle and changes in methods of production and consumption to combat this warning."
The encyclical is the highest level of teaching a pontiff can give, and it marks Pope Francis' strongest call to action on climate change yet.
Peter Williams, a Catholic writer and speaker for Catholic Voices, told Premier's News Hour: "An encyclical is one of the levels of authority that says to Catholics this is what you must be aware of and take account of when acting in the public sphere.
"So in this case it's going to be how we react when we come to problems with the environment, what policies we might try to prescribe in politics.
"So this is something that's giving basic moral principles that Catholics need to be aware of, take account of, and then act on.
"This is something that's very much within the remit of the judgement of individual Catholics as to how they act with regard to the environment and how politicians, Catholic politicians, should prescribe things to help the environment as well - and that's very much debatable, the church isn't going to make absolute stances on that."
Listen to Premier's Antony Bushfield speak to Peter Williams here: