President Trump appeared to troll teenage climate-change activist Greta Thunberg hours after she gave an emotional speech to global leaders at the UN on Monday — and she quickly clapped back.

“She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!” Trump wrote of Thunberg in a tweet late Monday, posting some video footage of the 16-year-old Swedish student’s both teary and blistering speech along with it.

Thunberg — who has become the global young face of anti-greenhouse-gas activism — fired back by changing her Twitter profile to say, “A very happy young girl looking forward to a bright and wonderful future. ”

In her address to the UN Climate Action Summit a day earlier, Thunberg fumed to the crowd, “How dare you?

“This is all wrong. I shouldn’t be up here. I should be back in school on the other side of the ocean,” she said, her voice breaking at times.

“Yet you have come to us young people for hope. How dare you? You have stolen my dreams and my childhood with your empty words,” said the young activist, who recently sailed across the Atlantic aboard a zero-carbon sailboat.