Pope Francis on Saturday told oil executives and other key energy sector figures at the Vatican that the world’s transformation to clean energy was an "epochal" challenge, and that companies' continued search for new sources of fossil fuels was "even more worrying" than the already high levels of greenhouse gases in the atmosphere.

Why it matters: Pope Francis, one of the most recognized figures in the world, is helping to fill the void in climate leadership that was left when the U.S. withdrew from the Paris Agreement on climate. The talks he called address what might be the central issue of the climate debate head on: that the energy companies that helped produce much of the greenhouse gasses in the atmosphere must also be a central part of any solution to the problem.

The event: In what Vatican officials said was intended to be a low key event, the pontiff invited 40 top energy executives, investors, and other experts in order to appeal to them to find a way to address what he called "two great needs of today’s world" at the same time: caring for the poor and being caretakers of the environment.

Situational awareness: As Axios' Amy Harder has expressed, the June 8-9 conference fell between two key dates: just after the one-year anniversary of the Donald Trump’s announcement the U.S. would be the only country to pull its support from the Paris Agreement, and just before the third anniversary of the release of Francis' only papal encyclical, Laudato si’, which formally made "Care for Our Common Home" — the environment — Catholic doctrine.

The big picture: Sources in Italy say the pope hosted smaller-scale talks on sustainable development focusing on limiting population growth last November that was controversial in Catholic circles because it included discussions about birth control. Another round of climate related talks may be held at the Vatican later in the year.

• It is clear that Pope Francis plans to play a protagonist role as the problems of development, climate, and energy converge even as he addresses other key issues for the church including terrorism, relations with other faiths, and clerical abuse scandals.

The details: Aside from the pope’s Saturday address, very little is so far known about what happened behind the closed doors of the talks. But in his remarks, Francis repeatedly returned to the need for those in attendance to make dramatic moves without pulling any punches about the consequences.

Yes, but: At least two-dozen influential executives and energy leaders including the heads of BP, ExxonMobil, Eni, Equinor, and BlackRock traveled to the Vatican for the event, and Pope Francis is the spiritual leader of the world’s 1.3 billion Catholics. But there is a limit to how much can be accomplished in one sitting, even in that context.

• As with the high-profile release of Laudato si’ in 2015, proof of effectiveness will only become apparent with time. That comes as multilateral talks struggle to maintain the momentum from the Paris Agreement and environmental groups say that chances of keeping global temperature rise to within 1.5 or 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) compared to pre-industrial levels are rapidly diminishing.