Ugandan environmental activist Vanessa Nakate has made a powerful speech at a Youth4Climate event in the Italian city of Milan.
She told delegates that world leaders were lost and the planet had been damaged.
"Africa pollutes little but suffers a lot from the climate crisis," she said.
Ms Nakate also asked who was going to pay for the environmental destruction:
The Swedish climate activist, Greta Thunberg, has also spoken and accused world leaders of words that sound great but lead to no action.
She ended her speech by leading chants of "What do we want? Climate justice. When do we want it? Now!"
Nearly 400 young people taking part in the meeting will send ideas to be vetted by climate and energy ministers also meeting in Milan.
The best ideas will go to the Cop26 summit in Glasgow next month.
Scientists say people aged under 40 face an unprecedented life threatened by heatwaves, floods, and crop failures.