Greta Thunberg says people have 'underestimated the force of angry kids'.
The teenage climate activist made the comment during an interview earlier today.
Thunberg has just spent three weeks sailing from Virginia in the USA to Lisbon, Portugal.
She is on her way to the COP25 climate summit in Madrid. The event had been scheduled to take place in Chile but had to move to Spain due to civil unrest - meaning Thunberg had to cross the Atlantic.
She has chosen to sail and take trains instead of flying or driving in a bid to reduce her environmental impact, hitching a ride on a 48ft sailing catamaran called La Vagabonde, which uses solar panels and hydro-generators for power.
'We are angry'
Speaking to reporters in Lisbon, after being told some people view her as 'angry', Thunberg said: "People are underestimating the force of angry kids.
"We are angry, we are frustrated, and it's because of good reasons. If they want us to stop being angry, maybe they should stop making us angry."
Meanwhile, Chile's environment minister, Carolina Schmidt, praised Thunberg for her climate activism, saying: "She has been a leader that has been able to move and open hearts for many young people and many people all over the world. We need that tremendous force in order to increase climate action."