Vatican City | Arnold Schwarzenegger downplayed the Trump administration's climate scepticism Tuesday and threw his weight behind the Vatican's environmental initiative, saying individual choice, local regulations and the Catholic Church's moral leadership were far more important to “terminate” global warming.

Schwarzenegger was at the Vatican to headline a three-day climate conference marking the 10th anniversary of Pope Francis' landmark 2015 environmental encyclical, Laudato Si (Praised Be). The document, one of Francis' main legacies, cast saving God's creation as an urgent moral imperative and launched a broad, grassroots movement that Pope Leo XIV has fully embraced and made his own.

Schwarzenegger, the former Republican governor of California, has devoted time to environmental causes since leaving political office in 2011. His Schwarzenegger Climate Initiative is one of the backers of the Vatican conference, which is being held at the Holy See's newly inaugurated environmental educational centre in Castel Gandolfo south of Rome.

At a news conference, Schwarzenegger was asked about President Donald Trump's recent comments to the UN General Assembly, where he falsely said that climate change was a “con job.” Trump has long been a critic of climate science and policies aimed at helping the world transition to green energies like wind and solar. His administration has rolled back landmark regulations, withdrawn climate project funding and instead bolstered support for oil and gas production in the name of an “American energy dominance” agenda.

“Don't use the federal government as an excuse,” Schwarzenegger told the Vatican briefing. “It's an easy way out.”

He recalled his legal battles with the Bush administration over California's environmental regulations when he was governor, and a particular victory where “we said Hasta la vista, baby”, Schwarzenegger said, quoting his famous line from “Terminator 2.”

Schwarzenegger said far more important were individual choices about turning off lights when you leave a room and state policies promoting solar power. With its 1.4 billion people, 400,000 priests the Catholic Church also has a critical mass of people who can back environmental initiatives, he said.