Pope Francis' ground-breaking and eagerly-awaited encyclical on climate change has been formally published on Thursday, making his stance on the "global problem" crystal clear.
The leader of the Catholic Church didn't mince his words in the public letter: "Climate change is a global problem with grave implications: environmental, social, economic, political and for the distribution of goods. It represents one of the principal challenges facing humanity in our day.
"If present trends continue, this century may well witness extraordinary climate change and an unprecedented destruction of ecosystems, with serious consequences for all of us."
The Pope also tweeted about the letter, titled "Laudato Si", which translates as "Praise Be".
The papal encyclical, a 180-page letter sent to 5,000 Catholic bishops worldwide, was published in five languages, and Pope Francis has said the document is "addressed to everyone", not just the world's 1.2bn Catholics.
He warns the worst impact of climate change in the coming decade will be felt by developing countries.
"Many of the poor live in areas particularly affected by phenomena related to warming, and their means of subsistence are largely dependent on natural reserves and ecosystemic services such as agriculture, fishing and forestry."
"It is remarkable how weak international political responses have been," Pope Francis said
Although there is much debate over the extent to which humans are responsible for global warming, the Pope does not shy away from his views.
"A number of scientific studies indicate that most global warming in recent decades is due to the great concentration of greenhouse gases released mainly as a result of human activity," he says.
"This century may well witness extraordinary climate change," he continues, adding if the situation does not change, there will be "an unprecedented destruction of ecosystems, with serious consequences for all of us".
"Human beings, while capable of the worst, are also capable of rising above themselves, choosing again what is good, and making a new start..
"..Every effort to protect and improve our world entails profound changes in lifestyles, models of production and consumption, and the established structures of power which today govern societies."
The Argentinian pontiff has spoken before on the effects of climate change on people and nature, but the encyclical comes ahead of a UN meeting to decide new "sustainable development goals" in September and crucial international talks aimed at securing a new global climate deal in Paris at the end of the year.
In a recent poll for Catholic aid agency Cafod, a third of Catholics in England and Wales say they will make their lifestyle greener if the pontiff makes an official statement on climate change.
The Pope has also attacked international powers on their lack of action, saying: "It is remarkable how weak international political responses have been.
"The failure of global summits on the environment make it plain that our politics are subject to technology and finance. There are too many special interests, and economic interests easily end up trumping the common good and manipulating information so that their own plans will not be affected."
Despite the Catholic Church's clashes with science, the encyclical uses scientific evidence to back up the reality of climate change, and even praises scientists' efforts to find solutions to the man-made problem.
After a draft copy of the encyclical was leaked, the Pope was heavily criticised, including by Jeb Bush, presidentital candidate for the United States.
The Republican politician, who opposes climate change action, said: "I don’t get economic policy from my bishops or my cardinal or my pope."
Tom Altmeyer, lobbyist for Arch Coal, the second biggest coalmining company, also joined in the critics, saying the Pope should promote fossil fuels, not condemn them.
"Industry, policymakers and social leaders – like Pope Francis – must work together to support policies that bring about new advances in fossil energy technologies so we can strike a balance between global economic needs and climate concerns," he said in an email.
Kofi Annan, Chair of the Africa Progress Panel and Kofi Annan Foundation, applauded the Pope for his "strong moral and ethical leadership".
"We need more of such inspired leadership. Will we see it at the climate summit in Paris?
"As Pope Francis reaffirms, climate change is an all-encompassing threat: it is a threat to our security, our health, and our sources of fresh water and food. Such conditions could displace tens of millions of people, dwarfing current migration and fuelling further conflicts."
Kumi Naidoo, International Executive Director at Greenpeace, said the organisation welcomed the "valuable intervention" of Pope Frances.
"This first encyclical on the environment brings the world a step closer to that tipping point where we abandon fossil fuels and fully embrace clean renewable energy for all, by the middle of the century.
"Everyone, whether religious or secular, can and must respond to this clarion call for bold urgent action.
"Above all, Pope Francis reminds all of us, individuals through to world leaders, of the moral imperative to address social and climate injustice. It is the poor who are most affected by catastrophic climate change, yet they have contributed least to causing the problem."