Nahlah Ayed reports from Vatican City:
Ask Canadian Father Michael Czerny what role he played in writing the Pope's 40,000-word letter on the destructive effects of climate change, and he only gives coy answers.
"Well, I'm part of the council," the Montreal native says with a laugh, referring to the Pontifical Council for Justice and Peace, charged with writing the first draft of Laudato Si, the Pope's manifesto on the environment.
But Father Czerny is anything but coy when asked whether Pope Francis is out of bounds — or out of his depth — intervening in the climate change debate in the first place.
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"Most of us aren't scientists, so that doesn't make him unusual. But all of us have to decide," Czerny told CBC News in an interview near his office in Rome.
"It's a real issue, and decision time is here."
Playing for maximum effect
It's hard to argue with that, when even divided world leaders have agreed to meet in Paris in November to discuss emissions and try to hammer out a strategy for dealing with man-made causes of climate change.
What is harder to ascertain is how much of a difference the Pope's intervention will make in bringing about a binding deal.
He's certainly playing for maximum effect.
The Pope was quick to deliver his view even as he began his first visit to the U.S., where his climate change message is likely to face the toughest audience yet.
Within four minutes of starting his speech at the White House today, Pope Francis said this: "… it seems clear to me also that climate change is a problem (that) can no longer be left to a future generation."
He spoke in English, a language he generally does not use, adding: "When it comes to the care of our common home, we are living at a critical moment in history. We still have time to make the change needed to bring about a sustainable and integral development. For we know that things can change."
The Pope launched his call for change early in the summer, surprising many by writing an entire encyclical, or papal letter, on climate change and its destructive effects on the planet as well as people — mostly the poor.
In a package designed to have wide appeal, the Pope called for dialogue, linking climate change to capitalism, and preaching a whole different way of life.
Not only did he speak plainly of the urgent need to cut carbon emissions, but put the blame both on "highly polluting fossil fuels" and a "throwaway culture."
He spoke extensively about the "tragic effects" on the world's poorest, using phrases like "self destructive," and the "damage we have done."
"The real point is to encourage leaders and citizens, and everyone, to face the issues," Father Czerny said. "It looks like a serious decision about the use of fossil fuels is absolutely essential. What we cannot do is continue burning them and just trust blindly that things are going to work out alright."
Tipping the balance?
The Pope's blunt intervention was naturally welcomed by environmentalists the world over, who were thrilled to have such a powerful man of God on their side.
In theory, with 1.2 billion followers, the Pope could tip the balance, ensuring faith trumps all other interests getting in the way of fighting climate change.
But it's not that simple.
The Pope also immediately faced criticism, some of the harshest from prominent fellow Catholics from the world's cradle of capitalism.
"I think religion ought to be about making us better as people and less about things that end up getting in the political realm," said Jeb Bush, a candidate for the Republican party leadership.
Rick Santorum, another candidate, was even more brusque.
"We probably are better off leaving science to the scientists, and focusing on what we're really good at, which is theology and morality."
Incongruously, talk show host Bill Maher, a known atheist, defended the Pope and tore into Santorum for his criticism of the Pope.
"He's the vicar of Christ, your God - shouldn't you have the humility to say, well, 'if the Pope thinks climate change is a problem, maybe I should?'" Maher said to Santorum.
The Pope even had the backing of some who you might think would have serious issues with more controversial Catholic positions, such as those relating to divorce or homosexuality — from prominent environmentalist Naomi Klein, to New York Mayor Bill de Blasio.
Push for action
Seemingly impervious to the criticism and the debate, the Pope charged ahead over the summer, organizing a conference to which Klein was invited, and a gathering of mayors — engaging a level of government further along in fighting climate than many national ones.
Vancouver's mayor, Gregor Robertson, was the only Canadian invited.
"The Pope and his team did his homework and found out where there are city leaders … who are pushing the pace and who are providing leadership on climate change," Robertson said in an interview from Vancouver.
"We have a national government that is deplorable on climate change," he added.
"I believe (the Pope's) voice is really important in really shifting us into high gear."
Other Popes have spoken out about the environment, but none made it such a priority. Pope Francis is essentially putting "doing your part" for the environment into the realm of obligation.
But will it translate into action — from leaders or from ordinary people?
"He says 'what kind of a world do we want to leave for our children,'" said Czerny. "So if it doesn't matter, go ahead and live as you used to live.
"But if it matters and if you realize that the way you are consuming, producing and so on is having an effect, then that's an important decision, and you can't just hope for the best."
Pope Francis may well just be preaching to the converted. But it may also be the best test yet of his actual power to bring about change.