The Pope confronts climate change deniers and calls for a "cultural revolution" over climate change in his new encyclical today. He spells the need for a new partnership between science and religion and warns that humans can no longer afford to see themselves as "lords and masters" of the earth.
Among many suggestions he says fossil fuels must be replaced urgently by renewable energy sources to help save the world from man-made global warming.
The Pope warns: "Climate change is a global problem with serious implications, environmental, social, economic, political and for the distribution of goods; it represents one of the principal challenges facing humanity in our day. Its worst impact will probably be felt by developing countries in coming decades."
Pope Francis has already been condemned by the right wing of the Republican Party in the US, including by influential Catholics, after a leaked copy of the encyclical made clear that he was not afraid to embrace political thought associated with the left to get his message home.
Archbishop of Westminster Cardinal Vincent Nichols, speaking against the backdrop of the business centre of Canary Wharf from the roof of an ecologically-constructed Catholic primary school, said the heart of his encyclical ran counter to traditional capitalism. He said the aim of the Church was to bring about a change from profit being the primary goal of capitalism, to one where ethics ruled instead.
From many other religious leaders, such a message would gain little traction. But the language used is accessible and immediate. It is a far cry from the theological obtuseness of some of his predecessors, and will quickly enter the consciousness of the modern media age, especially the young, adding further to its impact.
The unprecedented popularity of this Pope combined with the growing scientific evidence underpinning much of his argument, with floods, drought, rising temperatures and other extreme weather conditions causing terrible humanitarian disasters in some of the world's most deprived countries, means its rejection by the wider world is not a given. In September the Pope will travel to the US and address the UN General Assembly as world leaders gather to agree sustainable development goals. There is growing recognition that he might even achieve his goal of having a significant influence on the outcome of the UN climate conference in Paris in December.
In the 192-page encyclical, titled Laudato Si, or Be Praised, On the Care of Our Common Home, the Pope writes damningly: "We have come to see ourselves as her lords and masters, entitled to plunder her at will. The violence present in our hearts, wounded by sin, is also reflected in the symptoms of sickness evident in the soil, in the water, in the air and in all forms of life."
Consumerism is one root of climate change, he says. "These problems are closely linked to a throwaway culture which affects the excluded just as it quickly reduces things to rubbish."
Another is "a model of development based on the intensive use of fossil fuels, which is at the heart of the worldwide energy system."
The Pope says: "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 habit of wasting and discarding has reached unprecedented levels among the wealthy, he adds, condemning such "exploitation" of the planet. "Never have we so hurt and mistreated our common home as we have in the last two hundred years."
Making clear his agenda of influencing debate at the highest levels, Pope Francis says: "It is remarkable how weak international political responses have been." He says the lessons of the global financial crisis have not yet been learned, and says the market itself is not able to put things right.
Cardinal Nichols said he was "very proud" of the stand taken by the Pope. "He approaches what is well-recognised as a crisis in the world's climate from its impact on the poor. The voice of the poor comes through again and again."
Neil Thorns, director of advocacy at the Catholic aid agency CAFOD, said: "The Pope has deliberately released the encyclical in a year of key UN moments that will affect humanity, and today he says that climate change is real, urgent and it must be tackled. He is reading the signs of his times and telling us that the human and environmental costs of our current way of life are simply too high.
"Given our definition of progress has seen the poor excluded and the Earth degraded, we need to redesign our global economic system, businesses need to change the way they operate and we have to redefine our relationships with people and the Earth. Our response to the Pope's message can't simply be short-term tinkering at the edges of our current system but to take the bold decisions now which the poorest people around the world are crying out for."
US scientists also so spoke up in favour. Katharine Hayhoe, climate scientist at Texas Tech University and an evangelical, said the encyclical was important because it addressed moral values as well as facts. She said: "We have to connect these issues with our values." She said the letter shows up the "cognitive dissonance" in using religious arguments to endorse climate change denial, such as saying that God would not let global warming happen in the first place.
Michael Greenstone, aof the University of Chicago's Energy Policy Institute, said climate change denial was becoming "increasingly uncomfortable and complicated" and the Pope's statement will make it even harder. "I think the dam will break at some point. The arc of history bends towards truth."
According to a new Pew Research Center poll, 45 per cent of Americans and 47 per cent of US Catholics blame humans for global warming.
Father Thomas Reese, a Catholic priest who writes the National Catholic Reporter, said the encyclical will raise the climate conversation to another level.
"Suddenly, you're not just doing it for the polar bears, you're doing it for God. I think it makes a big difference."
UN climate change chief Christiana Figueres said the encyclical will influence this year's climate talks.
However, Catholic Republican presidential candidate Jeb Bush said he did not get his economic policy from his bishops, cardinals or Pope and nor would he let them influence him on the environment. Rick Santorum also questioned whether the Pope was credible on the issue of climate science.