Thunberg's activism started after convincing her parents to adopt several lifestyle choices to reduce their own carbon footprint. In August 2018, at age 15, she started spending her school days outside the Swedish parliament to call for stronger action on climate change by holding up a sign reading Skolstrejk för klimatet (School strike for climate). Soon, other students engaged in similar protests in their own communities. Together, they organised a school climate strike movement under the name Fridays for Future. After Thunberg addressed the 2018 United Nations Climate Change Conference, student strikes took place every week somewhere in the world. In 2019, there were multiple coordinated multi-city protests involving over a million students each.[6] To avoid flying, Thunberg sailed to North America where she attended the 2019 UN Climate Action Summit. Her speech there, in which she exclaimed "how dare you", was widely taken up by the press and incorporated into music.
For about two years, Thunberg challenged her parents to lower the family's carbon footprint and overall impact on the environment by becoming vegan, upcycling, and giving up flying. She has said she tried showing them graphs and data, but when that did not work, she warned her family that they were stealing her future.