VATICAN CITY (Reuters) - Pope Francis will call on all people to be "stewards of creation" and address the hot-button topic of climate change on Thursday in the most feverishly awaited papal encyclical in decades.
By making environmental protection a moral imperative, his intervention could spur the world's 1.2 billion Catholics to lobby policymakers on ecology issues. Francis has already used his two-year-old papacy to lead in areas such as the resumption of diplomatic ties between Cuba and the United States, a deal the Vatican brokered.
Francis has said he wants the document, called "Laudato Si (Be Praised), On the Care of Our Common Home," to be part of the debate at a major U.N. summit on climate change later this year.
Speaking to tens of thousands people in St. Peter's Square on Sunday, he said it was "addressed to everyone". He hoped it could spark "renewed attention to situations of environmental degradation and to recovery" and lead to "greater responsibility for the common home that God has entrusted to us".
People familiar with the encyclical say it will note the impact of climate change on the poor and discuss inequalities of wealth -- already a major theme for the first pope from Latin America, where poverty is widespread -- and population issues. Rich nations will be asked to re-examine "throw-away" lifestyles.
Politicians have increasingly acknowledged religion's role in the environmental debate, although anxious conservatives and climate change sceptics, particularly in the United States, have excoriated the pope for delving into science.
"If you are concerned about God, a creator and his creation, then you have to be concerned that his creation is not destroyed," said French Foreign Minister Laurent Fabius, who will host the make-or break summit in Paris from Nov. 30-Dec 11.
The first papal encyclical, or teaching letter, dedicated to the environment is expected to have particular sway over Latin American nations whose votes could be crucial at the summit.
The Vatican will hold a private briefing for ambassadors from some 170 countries after it is published on Thursday. "I have strict orders, as do many of my colleagues, to send it instantly to my government," said one ambassador.
Much of the pre-publication frenzy has focused on what it might say about climate change. Environmental activists are hoping to use the pope's words as a big gun in their arsenal to clinch international agreements to stem global warming.
Persons familiar with the document say it gives credence by default to scientific consensus that much of global warming is caused by human activity but that neither climate change activists or sceptics will be able to claim total victory.
Francis took his name from St. Francis of Assisi, patron of ecology and the title of the encyclical comes from one of the saint's prayers in praise of nature.
The pope hinted at what he would say while talking to reporters about climate change in January.
"I don't know if it is all (man's fault) but the majority is, for the most part, it is man who continuously slaps down nature," he said. "I think man has gone too far ... thank God that today there are voices that are speaking out about this."
At a conference at the Vatican in April, the Holy See teamed up with the United Nations and came down firmly against sceptics who deny human activities help change global weather patterns.
The final statement of the conference, attended by U.N. Secretary General Ban Ki-Moon and some 60 scientists, religious leaders and diplomats, said "Human-induced climate change is a scientific reality ..."
U.S. Republican presidential candidate Rick Santorum, a Catholic and climate change sceptic, said the Church would be "better off leaving science to the scientists".
Maureen Mullarkey, a commentator for the conservative U.S. website First Things, published by The Institute on Religion and Public Life, called Francis "an ideologue and a meddlesome egoist" who was "sacralizing politics and bending theology to premature, intemperate policy endorsements (on climate change)."
A papal encyclical is part of a pope's "ordinary magisterium", or teaching function, meaning it is authoritative but not infallible.
"He doesn’t thereby canonise or dogmatise a scientific theory, which by its very nature is subject to falsification and revision," said John Cavadini, professor of theology and director of the Institute for Church Life at the University of Notre Dame in the United States.
"But it is within the pope’s competence and authority to call attention to our moral responsibilities and duties in the face of the best scientific theory out there, especially when the consequences of not doing so are serious or even drastic, and where silence could be interpreted as scandalous," he said.
Additional reporting by Alister Doyle; Editing by Catherine Evans