U.N. Secretary General Ban Ki-moon met with Pope Francis, following a climate change summit hosted at the Vatican, titled "Protect the Earth, Dignify Humanity." (United Nations)

Following a closely watched Vatican climate change meeting Tuesday at the Pontifical Academies of Sciences and Social Sciences, the attendees — including not only scientific leaders but also religious and political luminaries — have released a statement (PDF here) suggesting that a 2015 climate accord may be the last chance to keep global warming within a range deemed “safe” for the world, its people and its ecosystems.

Meeting attendees included U.N. Secretary General Ban Ki-moon, Cardinal Peter Turkson, who heads the Pontifical Council of Justice and Peace, and Columbia University economist Jeffrey Sachs. The event is widely seen as a kind of prelude to a much anticipated papal encyclical expected this summer, in which Pope Francis will address the environment and humanity’s moral responsibility to care for it.

[Why Pope Francis is about to make a dramatic wave in the climate debate]

For now, the conference statement declares that “Human-induced climate change is a scientific reality, and its decisive mitigation is a moral and religious imperative for humanity.” And it points very directly at an unfolding international process for addressing it, suggesting that this process must succeed — at the end of this year.

The process is being carried out under the U.N. Framework Convention on Climate Change,  whose meeting in late 2015 in Paris represents the next major attempt to achieve a worldwide agreement to tamp down on humanity’s emissions.

“The world should take note,” says the statement, “that the climate summit in Paris later this year (COP21) may be the last effective opportunity to negotiate arrangements that keep human-induced warming below 2-degrees C, and aim to stay well below 2-degree C for safety.”

The statement also says that “political leaders of all UN member states have a special responsibility to agree at COP21 to a bold climate agreement that confines global warming to a limit safe for humanity, while protecting the poor and the vulnerable from ongoing climate change that gravely endangers their lives.”

Many in the environmental and scientific community think that if Pope Francis injects himself into international climate politics in an equally blunt fashion later this year, the ramifications on the climate debate could be dramatic.

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