REYKJAVÍK, Iceland—When President Donald Trump pulled the United States out of the Paris Agreement on climate change, it seemed like the entire world rushed to condemn him.

Emmanuel Macron, the president of France, immediately made a live broadcast. “He is making a mistake for the future of his country and his people, and a mistake for the future of the planet,” he said.

Bishop Marcelo Sánchez Sorondo, the head of the Pontifical Academy of Sciences at the Vatican, declared the withdrawal “a disaster for [the United States] and also for all the world.”

And 25 countries—including Chile, Switzerland, and this small, volcanic nation in the North Atlantic—banded together to make a joint statement. “Our commitment to the Paris Agreement is unshakeable,” it said. “We have every reason to fight for its full implementation: our families, our health, our welfare, our security, our economies, and our livelihoods.”

That torrent of global opprobrium rained down on Trump a month ago. This weekend, the leaders of the world’s 20 largest economies could deliver their censure to the president again, when they meet in Hamburg, Germany, at the G20 conference. So will they?

It’s still unclear. Germany and other western European countries had hoped to issue a unity statement on the treaty, creating a quasi-“G19” that continues to abide by the Paris Agreement while the United States dallies. There’s some precedent for this: Last month, at a meeting in Bologna, environmental ministers from six of the planet’s seven largest economies declared the Paris Agreement “irreversible, non-negotiable and the only instrument possible to combat climate change.” EPA Administrator Scott Pruitt and the rest of the American delegation, also in attendance at the meeting, were relegated to a footnote.