Happy Birthday Greta Thunberg! Greta Tintin Eleonora Ernman Thunberg turns 21 years old today. Here are five facts about the young climate activist. 1. She staged the first-ever climate school strike in 2018. 2. Thunberg refuses to fly and sailed across the Atlantic. 3. Her speeches are fact-checked by scientists. 4. She is the youngest 'TIME' Person of the Year ever. 5. Thunberg has been nominated for a Nobel Peace Prize. Happy Birthday, Greta Thunberg!