Thunberg's activism began by persuading her parents to adopt lifestyle choices that reduced 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 "" (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. To avoid energy intensive 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.