Activists take part in a pro-climate demonstration march in Lausanne, Switzerland September 27, 2019.

Students holding placards take part in the Global Climate Strike in Kathmandu, Nepal September 27, 2019.

People take part in a protest against climate change during an event in Tel Aviv, Israel September 27, 2019.

Climate change demonstrators hold a sign "All for the climate" during a protest in central Stockholm, Sweden September 27, 2019. TT News Agency/Claudio Bresciani via REUTERS

Hellevi Estama's sign reads "I want to teach my grandchildren how to ski" as she takes part in the Global Climate Strike at the Parliament House in Helsinki, Finland, September 27, 2019. Lehtikuva/Markku Ulander via REUTERS

Students display placards during a "Fridays for Future" march calling for urgent measures to combat climate change, in New Delhi, India, September 27, 2019.

Climate change environmental teen activist Greta Thunberg takes part in a climate strike march in Montreal, Quebec, Canada September 27, 2019.

People attend a protest demanding global politicians urgent actions to fight climate change in Madrid, Spain, September 27, 2019.

A student with painted face takes part in the Global Climate Strike in Kathmandu, Nepal September 27, 2019.

Activists of Extinction Rebellion sit on the street during a pro-climate demonstration march in Lausanne, Switzerland September 27, 2019.

People take part in a protest against climate change during an event in Tel Aviv, Israel September 27, 2019.

People take part in a protest against climate change during an event in Tel Aviv, Israel September 27, 2019.

A participant holds a dog with a placard during a protest march to call for action against climate change, in The Hague, Netherlands September 27, 2019.

A young woman carries a cardboard cutout depicting Greta Thunberg as she takes part in the Global Climate Strike of the movement Fridays for Future in Vienna, Austria September 27, 2019.

Young protesters march as part of the Global Climate Strike of the movement Fridays for Future in Vienna, Austria September 27, 2019.

Climate change demonstrators protest in Umea, Sweden September 27, 2019. TT News Agency/Erik Abel via REUTERS

Leo Korhonen and classmates from Koskela school take part in the Global Climate Strike at the Parliament House in Helsinki, Finland, September 27, 2019. Lehtikuva/Markku Ulander via REUTERS

Climate change teen activist Greta Thunberg meets David Suzuki before joining a climate strike march in Montreal, Quebec, Canada September 27, 2019.

Activists stage a performance during an environmental demonstration, part of the Global Climate Strike, in Warsaw, Poland September 27, 2019. Maciek Jazwiecki/Agencja Gazeta via REUTERS

Demonstrators take part in the Global Climate Strike at the Parliament House in Helsinki, Finland, September 27, 2019. Lehtikuva/Markku Ulander via REUTERS

Activists of Extinction Rebellion take part in a pro-climate demonstration march in Lausanne, Switzerland September 27, 2019.

Schoolchildren, students and activists attend a protest march to call for action against climate change, in The Hague, Netherlands September 27, 2019.

A participant holds a drawing depicting Swedish environmental activist Greta Thunberg during a protest march to call for action against climate change, in The Hague, Netherlands September 27, 2019.

A protestor holds up a sign during a march as part of the Global Climate Strike of the movement Fridays for Future in Vienna, Austria, September 27, 2019.

Activists attend the Fridays for Future global climate strike in Stockholm, Sweden September 27, 2019. TT News Agency/Anders Wiklundi via REUTERS

People stage a die-in during a "Fridays for Future" march calling for urgent measures to combat climate change, in New Delhi, India, September 27, 2019.

Students shout slogans during a "Fridays for Future" march calling for urgent measures to combat climate change, in New Delhi, India, September 27, 2019.

A participant holds a replica depicting globe on fire during a "Fridays for Future" march calling for urgent measures to combat climate change, in Mumbai, India, September 27, 2019.

Canada's Prime Minister Justin Trudeau greets Swedish climate change teen activist Greta Thunberg before a climate strike march in Montreal, Quebec, Canada September 27, 2019.

Climate change teen activist Greta Thunberg looks at the tassel from a gift given by Assembly of First Nations National Chief Perry Bellegarde before joining a climate strike march in Montreal, Quebec, Canada September 27, 2019.

People hold placards during a protest to demand action on climate change in Lisbon, Portugal, September 27, 2019.

A child holds a placard during a global climate change strike rally in Nicosia, Cyprus September 27, 2019.

People take part in a climate change strike in Toronto, Ontario, Canada September 27, 2019.

South Korean students attend a rally to demand action on climate change in Seoul, South Korea, September 27, 2019. Yonhap via REUTERS

Police officers carry a protester during a pro-climate demonstration march in Lausanne, Switzerland September 27, 2019.

Demonstrators take part in the Global Climate Strike at the Parliament House in Helsinki, Finland, September 27, 2019. Lehtikuva/Markku Ulander via REUTERS

Image used for illustrative purpose. People take part in a climate change strike in Toronto, Ontario, Canada September 27, 2019.

Students holding placards take part in the Global Climate Strike in Kathmandu, Nepal September 27, 2019.