When former President Barack Obama spoke to a leadership forum in India’s capital on Friday, he never once used the words “Donald Trump” and was careful to avoid any direct reference to his successor in the White House.

Yet Obama made plenty of veiled references, from climate change to the perils of using Twitter. The responses often drew laughter from the audience at the Hindustan Times Leadership Summit, which was part of a three-country tour Obama is undertaking in one of his first global outings as a private citizen after leaving office.Obama said he uses spellcheck and punctuation.

“Which my daughters think is odd. They were explaining to us how if you put a period at the end of a sentence it sounds harsh. I said, ‘No, that’s English. That’s how you know the thought is finished.’”

He said he sees people getting in trouble for their tweets, and says they should follow the old advice of thinking before you speak: “Think before you tweet,” Obama said. “Same principle.”

He said social media is a powerful tool, for both good and ill. “And look, I’ve got 100 million Twitter followers. I actually have more than other people who use it more often.”

(For the record, Obama has 97 million Twitter followers and Trump has 44 million).

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CLIMATE CHANGE

Obama said he could have a debate about climate change with people who said fossil fuels were necessary for growth in poorer nations like India or people who said humans should adapt. But he said he couldn’t debate with people who claimed it wasn’t real.

“If you’re saying it’s a hoax, then there’s no way for us to bridge our differences in a constructive way,” Obama said.

Trump has previously called climate change a hoax.

Obama praised India for helping forge the Paris climate agreement, which he signed last year but which Trump said he planned to withdraw from.

“It’s an agreement, even though we have a little bit of a pause in American leadership, that is giving our children a fighting chance,” Obama said.

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LEADERSHIP

Obama said politicians usually reflect public opinion.

“And so if you see a politician doing things that are questionable, one of the things as a citizen is to ask yourself ‘Am I encouraging, or supporting or giving license to the values I’m hearing out of the politician?’” Obama said. “Because frankly, politicians tend to be more of a mirror and more of a reflection of forces in the society.”