Teenage climate activist Greta Thunberg appears to have shrugged off Donald Trump’s latest attack on her, delivering a silent slapdown to the US President.

The broadside came after Ms Thunberg was named Time magazine’s 2019 person of the year on Thursday, for her work inspiring millions of young people to take action against climate change.

The Swedish teenager has become a symbol of a growing movement of young climate activists after leading weekly school strikes in her country that inspired similar actions in about 100 cities worldwide.

The magazine’s announcement prompted a scathing attack from Mr Trump, who took to Twitter on Friday morning (AEDT) to advise the 16-year-old Swedish teenager to work on “her anger management problem”.

“So ridiculous. Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!” Mr Trump, 73, wrote.

So ridiculous. Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill! https://t.co/M8ZtS8okzE

— Donald J. Trump (@realDonaldTrump) December 12, 2019

Ms Thunberg didn’t take too long to respond, and when she did it came silently. She updated her Twitter biography to read: “A teenager working on her anger management problem. Currently chilling and watching a good old-fashioned movie with a friend.”

The spat between the teenager and the world’s most powerful man propelled Ms Thunberg to trend on Twitter with several hashtags. It came on the fourth anniversary of the Paris climate pact that Mr Trump withdrew from soon after taking office.

Greta Thunberg’s updated Twitter profile on Friday. 

It was not the first time the US President has targeted the Swedish teenager.

In September, he retweeted a clip of Ms Thunberg’s to a UN climate summit – in which she angrily denounced world leaders for failing to tackle climate change.

“She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!” was Mr Trump’s sarcastic commentary.

Ms Thunberg took the same approach then, changing her Twitter biography to describe herself as “a very happy young girl looking forward to a bright and wonderful future”.

Greta must work on her anger management problem? Are you serious? I can’t believe Trump is this petty, dumb, and blackhearted to bully a 16-year-old kid out of pure jealousy that she made the cover of Time Magazine for Person of the Year over him. Trump needs to deal with it.

— Eugene Gu, MD (@eugenegu) December 12, 2019

It appears that might be the teen activist’s way of dealing with her powerful opponents. Mr Trump’s mockery came just days after Brazilian President Jair Bolsonaro described her as “pirralha” – the Portuguese word for “brat”.

“It is staggering, the amount of coverage the press gives that brat,” said Mr Bolsonaro, who has faced mounting scrutiny over his commitment to the environment, particularly after this year’s devastating fires in the Amazon.

Ms Thunberg responded by temporarily adding “pirralha” to her Twitter bio.

Mr Trump was also shortlisted for this year’s Time magazine person of the year. He won the title in 2016 after beating Hillary Clinton in the US presidential election.

-with AAP