Greta Thunberg speaks at an event with other climate activists on April 22, 2019 in London, England.

Teenage climate change activist Greta Thunberg said on Monday that talking to U.S. President Donald Trump at a United Nations summit on global warming would have been a waste of time since he would not have paid any attention.

In an interview with BBC radio's Today program, for which she was the guest editor on Monday, Thunberg also said she regarded personal attacks on her as funny and she hoped to go back to having a normal life.

A video of the 16-year-old Swedish campaigner giving Trump what media described as a "death stare" at a U.N. climate summit in New York in September went viral on social media. Trump has questioned climate science and is pulling the United States out of the 2015 Paris Agreement on global warming.

Asked what she would have said to the president if they had spoken, Thunberg said: "Honestly, I don't think I would have said anything because obviously he's not listening to scientists and experts, so why would he listen to me?

"So I probably wouldn't have said anything, I wouldn't have wasted my time," she said.

This month Brazilian President Jair Bolsonaro called Thunberg "a brat." Trump has said on Twitter she needs to work on her anger management problem.

"Those attacks are just funny because they obviously don't mean anything," she said. "I guess of course it means something — they are terrified of young people bringing change which they don't want — but that is just proof that we are actually doing something and that they see us as some kind of threat."

Thunberg came to world attention when she began a grassroots campaign aged 15 by skipping school every Friday to demonstrate outside the Swedish parliament. The protests have inspired millions of young people to take action against climate change.