Key experiences that influenced the environmental activism of Greta Thunberg included her personal struggle with Asperger's syndrome, which shaped her perspective on climate change and the urgency of action. Thunberg became aware of the climate crisis at a young age, leading to her solitary school strike for the climate in 2018, which ignited a global movement. Her direct communication style and determination have inspired millions to advocate for sustainability and environmental justice, highlighting the need for immediate action against global warming and ecological degradation.