Swedish campaigner Greta Thunberg has made a passionate speech to world leaders at the UN, accusing them of failing to act on climate change.
"You have stolen my dreams and my childhood with your empty words," she told a UN climate summit in New York.
About 60 world leaders are taking part in the one-day meeting organised by UN Secretary General António Guterres.
He earlier said countries could only speak at the summit if they came with action plans to cut carbon emissions.
US President Donald Trump, a climate change sceptic, had not been expected at the meeting - but he was briefly spotted in the audience.
What did Greta Thunberg say?
In an emotional speech, she said: "This is all wrong. I shouldn't be up here. I should be back in school on the other side of the ocean, yet you all come to us young people for hope. How dare you?
"You have stolen my dreams and my childhood with your empty words," the 16-year-old said.
And she urged world leaders to act urgently, saying: "We will be watching you."
What did world leaders say?
Mr Guterres, who organised the meeting, said the world was "in a deep climate hole" and that urgent action was needed.
"Time is running out, but it's not too late," he said.
German Chancellor Angela Merkel said her country would double to €4bn (£3.5bn; $4.4bn) it financial commitment to fight global warming.
French President Emmanuel Macron said international organisations had pledged to release $500m in additional aid to protect tropical forests.
New Zealand's Prime Minister Jacinda Ardern said things "are starting to turn around" in the country.
"Our gross emissions peaked in 2006, over 80% of our electricity already comes from renewable hydro and wind, and we have begun an ambitious agenda.
"We have introduced in parliament the zero carbon bill, the purpose of which is to ensure New Zealand lives within the threshold of 1.5C of global warming necessary to avoid catastrophic weather events for our Pacific neighbours."
Scientists' warning
The summit comes days after several million people took part in a global climate strike led by youth activists.
Ahead of the meeting, scientists warned the signs and impacts of global warming were speeding up.
The World Meteorological Organization (WMO) said the amount of carbon dioxide going into the atmosphere between 2015 and 2019 had grown by 20% compared with the previous five years.
"We should listen to the loud cry coming from the schoolchildren," said Professor Brian Hoskins, chair of the Grantham Institute, Imperial College London, and professor of meteorology at the University of Reading.
"There is an emergency - one for action in both rapidly reducing our greenhouse gas emissions towards zero and adapting to the inevitable changes in climate," he said.