In August 2018, Greta Thunberg started a school strike for the climate outside the Swedish Parliament that has since spread all over the world and now involves over 100,000 schoolchildren. The movement is now called Fridays For Future.

Thunberg has spoken at climate rallies in Stockholm, Helsinki, Brussels and London. In December 2018 she attended the United Nations COP24 in Katowice, Poland, where she addressed the Secretary-General and made a plenary speech that went viral and was shared many million times around the globe. In January 2019, she was invited to the World Economic Forum in Davos where her speeches again made a worldwide impact.

Thunberg tries to live a low-carbon life. Therefore she is vegan, and she doesn't fly. In 2019, TIME magazine named her Person of the Year as well as one of the world's 100 most influential people.