Activists attend an environmental demonstration, part of the Global Climate Strike by "Fridays for Future" movement, calling for global strikes on Black Friday, a week ahead of the United Nations' COP25 Climate Change Summit, in Warsaw, Poland November 29, 2019.

High school students hold placards and shout slogans during a protest to demand action on climate change as part of the Global Climate Strike of the movement Fridays for Future in Athens, Greece, November 29, 2019.

Israelis take part in the "Fridays for Future" global strike against climate change, in Tel Aviv, Israel November 29, 2019.

Youth for Climate activists demonstrate during a day of protest to denounce the annual Black Friday shopping frenzy in Marseille, France, November 29, 2019.

Activists hold a banner during a protest march to call for action against climate change, in Vienna, Austria, November 29, 2019.

People take part in a "Fridays for Future" march calling for urgent measures to combat climate change, in Mumbai, India, November 29, 2019.

Students and activists hold placards with messages as they participate in a Global Climate Strike rally calling for urgent measures to combat climate change, in New Delhi, India, November 29, 2019.

A person holds a placard during a protest to demand action on climate change as part of the Global Climate Strike of the movement Fridays for Future, in Lisbon, Portugal, November 29, 2019.

A climate change activist holds a banner as she stages a 'drop dead' flashmob protest against climate change consequences at Lumpini Park in Bangkok, Thailand November 29, 2019.

Israelis take part in the "Fridays for Future" global strike against climate change, in Tel Aviv, Israel November 29, 2019.

Israelis take part in the "Fridays for Future" global strike against climate change, in Tel Aviv, Israel November 29, 2019.

Climate change activists lie on the floor as they stage a 'drop dead' flashmob protest against climate change consequences at Lumpini Park in Bangkok, Thailand November 29, 2019.

A climate change activist lies on the ground as they stage a 'drop dead' flashmob protest against climate change consequences at Lumpini Park in Bangkok, Thailand November 29, 2019.

People stage a die-in during a Global Climate Strike rally calling for urgent measures to combat climate change, in New Delhi, India, November 29, 2019.

Inflated balloons are seen during the Global Climate Strike of the movement Fridays for Future, in Cologne, Germany, November 29, 2019. REUTERS/Thilo Schmuelgen

Placards lay on the ground during a protest to demand action on climate change as part of the Global Climate Strike of the movement Fridays for Future, in Lisbon, Portugal, November 29, 2019.

A protester carries a sign that reads "Don't touch Virunga" during the climate protest in the streets of Kinshasa, Democratic Republic of the Congo November 29, 2019.

Youth for Climate activists demonstrate inside the Westfield Les 4 Temps shopping center during a day of protest to denounce the annual Black Friday shopping frenzy at La Defense business and financial district in Puteaux near Paris, France, November 29, 2019. The slogan reads "State of climate emergency".

People shout slogans during a protest to demand action on climate change as part of the Global Climate Strike of the movement Fridays for Future, in Lisbon, Portugal, November 29, 2019.

Protesters holding placards take part in the Global Climate Strike of the movement Fridays for Future, in Berlin, Germany, November 29, 2019.

A climate change activist takes part in a protest against climate change consequences at Lumpini Park in Bangkok, Thailand November 29, 2019.

Israelis take part in the "Fridays for Future" global strike against climate change, in Tel Aviv, Israel November 29, 2019.

Youth for Climate activists demonstrate during a day of protest to denounce the annual Black Friday shopping frenzy in Marseille, France, November 29, 2019.

Congolese band members participate in the climate protest in the streets of Kinshasa, Democratic Republic of the Congo November 29, 2019.

Studens holding placards attend the Global Climate Strike of the movement Fridays for Future, in Hamburg, Germany, November 29, 2019. The placard reads, "Stop climate crisis, stop GroKo".

People attend the Global Climate Strike of the movement Fridays for Future, in Cologne, Germany, November 29, 2019.

A child holds a placard during a 'drop dead' flashmob protest against climate change consequences at Lumpini Park in Bangkok, Thailand November 29, 2019. Image used for illustrative purpose.

Students and activists attend a protest march to call for action against climate change, in Vienna, Austria, November 29, 2019.

Schoolchildren carry banners during a march organized to coincide with the Fridays for Future and the global strike to stop global warming ahead of COP25 next mont, in Yaounde, in this handout picture obtained by Reuters on November 29, 2019, Cameroon. Greenpeace Africa/ Handout via REUTERS.