ATHENS -- A sightseeing trip to the Acropolis gave President Obama a break Wednesday from the primary mission of his European trip; assuring European leaders that President-elect Donald Trump won’t abandon them. ‎

As anti-American protesters took to the streets to mark his arrival, CBS News correspondent Margaret Brennan says Mr. Obama praised Greece as the birthplace of democracy, but warned there is a dark side to the type of populist movement led by Mr. Trump.

“We are going to have to guard against a rise in a crude sort of nationalism or ethnic identity or tribalism that is built around an ‘us and a them,’” Mr. Obama said.

The fast pace of economic and social changes has alienated people, he said, and leaders like Trump have successfully tapped into that anger. He called for a “course correction” in the West to ensure that all members of society benefit from the advances in technology and globalization.

Mr. Obama said societies that manged to foster greater equality were “less likely to turn on each other, less likely to appeal to some of the darker forces.”

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But his primary purpose in Europe remains quelling anxiety among the continent’s leaders that the new U.S. president could usher in a dramatic reversal of course on everything from security to global warming.

Mr. Trump’s climate change denial -- he’s called it a “hoax” -- has alarmed Europe’s leaders, as did his choice of well-known global warming skeptic Myron Ebell to lead his Environmental Protection Agency (EPA) transition team.

“We believe that the so-called global warming consensus was not based on science, but was a political consensus,” Ebell once said.

At a global climate change conference in Morocco, French president Francois Hollande said Trump cannot pull out of a recent international deal to cut greenhouse gas emissions, calling the Paris Agreement irreversible.

Hollande said the United States -- the largest economic power in the world and the second-largest greenhouse gas emitter -- must respect the commitments it has undertaken.