US President Donald Trump reprised his ridicule of 16-year-old Greta Thunberg on Thursday after the Swedish climate activist was named Time’s Person of the Year for 2019.

Thunberg won the magazine’s annual honorific on Wednesday for her work inspiring millions of young people to take action against climate change.

“So ridiculous. Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!” Trump, 73, wrote on Twitter, commenting on another person’s tweet congratulating Thunberg.

Thunberg responded by updating her Twitter biography to include: “A teenager working on her anger management problem. Currently chilling and watching a good old-fashioned movie with a friend.”

The spat, which propelled Thunberg to trend on Twitter with several hashtags, came on the fourth anniversary of the Paris climate pact that Trump withdrew from soon after taking office.

It was not the first time the Republican president targeted Thunberg.

In September, Trump retweeted a clip of the teenager’s speech to a United Nations climate summit in which she angrily denounced world leaders for failing to tackle climate change by demanding: “How dare you?”

His sarcastic commentary: “She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!”

Thunberg also changed her Twitter biography following that slight to describe herself as “A very happy young girl looking forward to a bright and wonderful future.”

Thunberg had also been a contender for the Nobel Peace Prize, an honour Trump covets.

Trump himself received the Time magazine designation in 2016 after he won the US presidential election over Democrat Hillary Clinton.

- Reuters