ROME — Barack Obama took his first step back onto the world stage on Tuesday, shedding his tie to give wide-ranging, if studiously nonpartisan, remarks during a food and technology conference in Milan.

First in a keynote address, during which he often consulted his notes, and then in a policy-heavy conversation with his former chef, Sam Kass, Mr. Obama spoke about how climate change was imperiling food production around the world and threatening to aggravate the “migration that has put such a burden on Europe.”

In a conversation that seemed intended to avoid making news, he also spoke about rain patterns, income inequality, privacy issues, his post-presidential life and cows. When President Trump was mentioned, Mr. Obama politely turned the page, saying that while “the current administration has differences with my administration in terms of energy policy,” he believed that “the private sector has already made a decision that the future is in clean energy.”

Since leaving office, Mr. Obama has kitesurfed with the billionaire Richard Branson, started writing his memoirs and begun earning speaking fees. Critics have accused Mr. Obama, who campaigned as a different kind of politician, of hypocrisy for accepting an offer of $400,000 to speak in September at a health care conference run by the Wall Street firm Cantor Fitzgerald.