He added: “I encourage you to keep your initiative, keep your mobilisation, and more and more to hold my generation accountable.”
Attending a UN Youth Climate Summit on Saturday, September 21, Ms Thunberg thanked the younger generations for showing initiative.
More than 700 young people took part in the climate conference.
She said: “Yesterday millions of people across the globe marched and demanded real climate action, especially young people.
“We showed that we are united and we young people are unstoppable.”