Teenage climate change activist Greta Thunberg has farewelled former US President Donald Trump with a clever tweet.

Thunberg used Trump's words against him as she wrote: "He seems like a very happy old man looking forward to a bright and wonderful future. So nice to see!"

The remark was just one of many Trump made about Thunberg in the past.

The quote came from Trump after Thunberg's address to the Davos summit in 2020, saying that she "seems like a very happy young girl looking forward to a bright and wonderful future."

Thunberg's tweet was a hit with fans, reaching over 690,000 likes on Twitter.

As many social media platforms banned Trump from using their services, he is unable to respond to Thunberg at this time.

This isn't the first time the two have had a war of words, with Trump claiming that Thunberg's 2019 Time "Person of the Year" was "so ridiculous".

"Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!" he tweeted at the time.

Thunberg sat on his words until Trump prompted electoral officials to "STOP THE COUNT" during the Presidential election race.

"So ridiculous. Donald must work on his Anger Management problem, then go to a good old fashioned movie with a friend! Chill Donald, Chill!" Thunberg tweeted.

Thunberg and Trump never met during his presidential term, with Thunberg saying it would have been a "waste of time".

"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?" she told BBC Radio 4.