Trump was responding to a tweet congratulating Thunberg by Roma Downey, an actress and producer from Northern Ireland. Her production credits include the History Channel miniseries, "The Bible," which she also starred in as Mary, mother of Jesus.
Thunberg wasted little time in offering a rejoinder. Shortly after his tweet, she had updated her Twitter profile to read: "A teenager working on her anger management problem. Currently chilling and watching a good old fashioned movie with a friend."
Trump, who has called climate change a "hoax," also took note of Thunberg in September, following an appearance at a United Nations climate summit where she offered an impassioned - and somewhat fatalistic - plea to global leaders.
"She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!" Trump wrote on Twitter at the time.
Thunberg subsequently embraced Trump's sarcastic description and altered her Twitter profile to describe herself to her followers as "a very happy young girl looking forward to a bright and wonderful future."
At her U.N. appearance, Thunberg chastised leaders for praising young activists like herself while failing to deliver on drastic actions needed to avert the worst effects of climate change, and she warned that if the world continued with business as usual, her generation would face an insurmountable catastrophe.
In explaining Time's choice of Thunberg as Person of the Year, the magazine's editor in chief, Edward Felsenthal, said Wednesday that "she became the biggest voice on the biggest issue facing the planet this year, coming from essentially nowhere to lead a worldwide movement."
Thunberg represents a broader phenomenon of young people pushing for change, Felsenthal said during an appearance on NBC's "Today" show. He pointed to the Parkland, Florida, high school students who became a leading voice on gun control, as well as to another finalist for 2019 Person of the Year: the Hong Kong protesters who have spent months in the streets urging democratic reform.
