"I'm of course, very grateful for that, very honored," Thunberg said, but added that "it should be everyone in the Fridays for Future movement because what we have done, we have done together."
Thunberg said she was hopeful that the message being pushed by her and other activists — that governments need to drastically increase their efforts to combat climate change — is finally getting through.
But she insisted that the media should also pay attention to other activists, particularly indigenous people who she said "are hit hardest by the climate and environmental crisis," and to the science around global warming.
"That is what I am trying to do, to use my platform to do," she said.
Thunberg said the movement, which has staged repeated worldwide protests attended by hundreds of thousands of people, had managed to spread awareness about the need to urgently reduce planet-warming greenhouse gas emissions and help those already affected by climate change.
"To get in a sense of urgency in the conversation that is very needed right now to be able to move forward," she said. "That, I think, is our biggest success."
Asked whether she thought world leaders were beginning to respond to this message, Thunberg said: "They say they listen and they say they understand, but it sure doesn't seem like it."
"If they really would listen and understand then I think they need to prove that by translating that into action," she added.
She said the experience of the past 15 months, going from solo-protester outside the Swedish parliament to speaking in front of world leaders at the U.N. General Assembly, had changed her.
"I think life is much more meaningful now that I have something to do that has an impact," she said.
Thunberg has tried to preserve some privacy despite the relentless interest she's received from media and adoring fans in recent months.
She was mobbed on her arrival in Madrid last week and the attention paid to her appearances at the climate conference has far outstripped that of other events, save for Hollywood stars like Harrison Ford.
"I would like to be left alone," Thunberg said when asked about her plans for the next days. She will later travel home to Sweden, to spend Christmas with her family and dogs, she added.
"After that, I have no school to return to until August because I've taken a gap year," she said.
"I will probably continue a bit like now, travel around. And if I get invitations to come. And just try everything I can," she added.
Earlier Wednesday, Thunberg addressed negotiators at the U.N.'s annual climate talks, warning that "almost nothing is being done, apart from clever accounting and creative PR."
Last year's Time winners included slain Saudi journalist Jamal Khashoggi; the staff of the Capital Gazette in Annapolis, Maryland, where five people were shot to death; Philippine journalist Maria Ressa; and two Reuters journalists, Wa Lone and Kyaw Soe Oo.
Kiley Armstrong in New York contributed to this report.