Time cover features Swedish teen climate activist Greta Thunberg named the magazine's Person of the Year for 2019 in this undated handout. Thunberg, who turns 17 in January and who is known for her blunt, straightforward speaking manner, has urged immediate action to address what she describes as the global climate crisis. TIME via REUTERS

Climate change activist Greta Thunberg attends a news conference during COP25 climate summit in Madrid, Spain, December 9, 2019. Thunberg launched a grassroots campaign aged 15 by skipping school every Friday to demonstrate outside Swedish parliament, pushing for her government to meet its ambitious goals to curb carbon emissions. REUTERS/Juan Medina

Climate change activist Greta Thunberg speaks at the High-Level event on Climate Emergency during the U.N. Climate Change Conference (COP25) in Madrid, Spain December 11, 2019. Thunberg, who turns 17 in January, is currently in Madrid at a United Nations climate summit where world leaders are wrangling over how to implement a 2015 Paris agreement designed to avert potentially catastrophic global warming. REUTERS/Susana Vera

Climate change activist Greta Thunberg attends the High-Level event on Climate Emergency during the U.N. Climate Change Conference (COP25) in Madrid, Spain December 11, 2019. Thunberg, who said her Asperger's syndrome can be an advantage in her campaigning, sailed across the Atlantic Ocean for 20 days to get to the Madrid event in order to avoid travelling by air. REUTERS/Susana Vera

Climate change activist Greta Thunberg speaks during the Unite Behind the Science event during COP25 climate summit in Madrid, Spain, December 10, 2019. REUTERS/Sergio Perez

Climate change activist Greta Thunberg arrives to attend the Unite Behind the Science event during COP25 climate summit in Madrid, Spain, December 10, 2019. REUTERS/Sergio Perez