Teen activist Greta Thunberg took her climate change fight to the US Congress, imploring the nation's lawmakers - several of whom are global warming sceptics - to "take real action" to avert environmental disaster.
The 16-year-old Swede was joined by other campaigners who said looming uncertainty caused by inaction over climate change has led younger generations to question the intentions of today's political leaders.
Thunberg arrived last week in Washington, where she has maintained a busy schedule: demonstrating in front of the White House, meeting indigenous leaders from South America and gathering on the US Supreme Court steps with children suing the government for climate inaction.
On Monday, she sat down with former president Barack Obama, and also received an Amnesty International award.
In Wednesday's appearance before a joint hearing of two House committees, her message was humble but blunt.
"I don't want you to listen to me, I want you to listen to the scientists," she said in a soft voice, noting that she wanted her opening testimony to be a 2018 United Nations report, which called for limiting global warming to 1.5°C.
"I want you to then unite behind the science - and then I want you to take real action."
Congress has been all but paralysed on a path forward to mitigate climate change in recent years.
US President Donald Trump has openly questioned the effects of a changing climate, and his Republican administration has rolled back several Obama-era regulations that were aimed at reducing industrial pollution, cleaning US waterways and protecting federal lands.
While congressman Garret Graves acknowledged that "aggressive action" is needed, he said it was critical to make "sure we're moving forward based on facts".
He and other Republicans also stressed that the world's second-largest economy, China, must take dramatic steps to stem its own emissions.
Beijing was given an "inappropriate" pass in the Paris climate accord because it allows China to have a 50% increase in its emissions by 2030, even as the US is limiting its emissions, Graves said.
The Trump administration abandoned the Paris accord in 2017.
Seventeen-year-old Jamie Margolin, co-founder of the group This Is Zero Hour, accused US lawmakers of being in bed with corporate interests including the fossil fuel industry.
Young advocates before Congress "pleading for a livable earth should not fill you with pride - it should fill you with shame", she said.
Lawmakers have spent countless hours with lobbyists for corporations that are "making millions of dollars off of the destruction of my generation's future", she added.
Margolis also told lawmakers they had no excuse not to do everything in their power to help stop climate change, for their children's sakes.
"Can you really look them in the eye and say 'No, sorry, I couldn't do anything because that country over there didn't do anything?'" she boomed. "That is shameful and that is cowardly."
House Democrats like Foreign Affairs Committee chairman Eliot Engel applauded Thunberg and her fellow activists, saying lawmakers "owe it to them to do what we can now to make sure that the world is saved".
But he also noted that "there are so many" in Congress who still deny the climate science.
Benji Backer, a 21-year-old conservative blogger and climate activist who testified, had a message for conservative lawmakers: "the climate is changing," and they must embrace "reasonable" approaches to addressing it.
He also offered Trump a message: "Climate science is real, it's not a hoax."
"I urge you to accept climate change for what it is, and to act accordingly," Backer said.
Greta burst to prominence when she upbraided delegates at the World Economic Forum in Switzerland early this year for their inaction on climate change.
On Wednesday US lawmakers sought her wisdom on how to inspire young people to get involved in the fight.
"Just tell them the truth" about the science, and the perils of climate change, Thunberg said.
"We need to inform them, and start treating this crisis like the existential emergency it is," she added. "Then I think people will understand and want to do something about it."