LONDON — Greta Thunberg says she needs a break.

The seemingly tireless 16-year-old climate activist — who has sailed across the Atlantic twice as she has become the most prominent face in the movement to fight global warming, and lectured the world’s leaders that they were not doing enough to address the problem — recently told reporters in Spain:

“I will be home for Christmas and then I will take a holiday break because you need to take rest. Otherwise you cannot do this all the time.”

The activist, who last week was named by Time magazine as its person of the year, has faced attacks from the far right, as well as from the president of the United States and other adults who find her intense and her message that the world is facing a crisis unsettling. Now others have weighed in, including a German railway company.

President Trump, who was Time magazine’s person of the year in 2016, called this year’s choice “ridiculous” on Twitter. He urged Ms. Thunberg to “work on her anger management problem” and to “chill.”

The Trump campaign also distributed a Photoshopped image of the Time cover with the president’s head superimposed on the teenager’s body.