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Leonardo DiCaprio was impressed when he met Greta Thunberg.
The actor shared his photo with the climate change activist on Instagram.
He hoped that "Greta's message was a waking call to world leaders around the world," and "the hour of inactivity is over."
He also praised the teenager for her work and said that she was "optimistic about what the future holds."
Since posted 22 hours ago, the images have liked nearly 4 million.
Greta Thunberg helped launch an international youth movement against climate change.
Swedish teenagers started a "school strike against the climate" in front of the Swedish parliament last August.
Her strikes inspire students from all over the world and lead tens of thousands of students from Germany, Japan, the UK, Australia and more to participate in #FridaysforFuture demonstrations.
Leo wrote:
"History will judge what we do today to enable future generations to enjoy the same living planet we took for granted."
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Greta Tunberg talks with protesters at an extinct uprising protest in London in April
Hollywood stars also mentioned environmental issues.
He believes that climate change is the biggest problem facing young people today, according to Newsbeat 2016.
He has a foundation that explains that he is dedicated to dealing with climate change and environmental threats to life on Earth.
His organization recently gave $ 5 million to help the Amazon rainforest after a recent fire.
"It's an honor to spend time with Greta. She and I have promised to support each other to ensure a brighter future for our planet."
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