President Trump called TIME's decision to name 16-year-old climate activist Greta Thunberg as its 2019 Person of the Year "so ridiculous" in a Thursday tweet.

"So ridiculous. Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!"

The big picture: Thunberg — who has openly discussed the fact that she has been diagnosed with Asperger's, which is on the autism spectrum — fired back by changing her Twitter bio to read, "A teenager working on her anger management problem. Currently chilling and watching a good old fashioned movie with a friend."

Thunberg pushed back against claims that she is "political" on Thursday afternoon, saying she has "never supported any political party, politician or ideology."

that she is "political" on Thursday afternoon, saying she has "never supported any political party, politician or ideology." She emphasized the need to discuss science of climate change "and the risks of failing to act on it" and "the fact that the politics needed don't exist today, neither to the right, left nor center."

of climate change "and the risks of failing to act on it" and "the fact that the politics needed don't exist today, neither to the right, left nor center." "That being said — some are certainly failing more than others," she added.

Flashback: Thunberg responded in September to another tweet from the president that mocked her demeanor and tactics, saying, "I honestly don’t understand why adults would choose to spend their time mocking and threatening teenagers and children for promoting science, when they could do something good instead."

Go deeper: Greta Thunberg addresses climate deniers' attacks and Trump's tweet