WASHINGTON (Reuters) - Swedish teenager Greta Thunberg, who has inspired a global movement for climate change, delivered a strong message to U.S. lawmakers on Wednesday: “Wake up.”

Wrapping up a six-day visit to Washington, D.C., the 16-year-old Thunberg rallied a room full of Democratic lawmakers and activists, urging them to follow scientific warnings and push for strong measures to combat climate change.

“This is not the time and place for dreams. This is the time to wake up,” Thunberg said behind a lowered podium at the ornate House of Representatives Ways and Means Committee room.

Thunberg spent the day in Congress and on the steps of the Supreme Court, lending her star power to join U.S and youth activists who were drumming up attention and support ahead of a global climate strike on Friday.

She began with a pointed message before a U.S. congressional hearing: “I don’t want you to listen to me. I want you to listen to the scientists.”

Thunberg, founder of the “Fridays For Future” weekly school walkouts to demand government climate-change action, submitted a 2018 report by the Intergovernmental Panel on Climate Change at the hearing in lieu of testimony. It urged rapid, unprecedented changes to the way people live in order to keep temperatures from rising by 1.5 degrees Celsius (2.7 Fahrenheit) by 2030.

“People in general don’t seem to be aware of how severe the crisis” is, Thunberg said, urging lawmakers to “unite behind the science” and take action, saying that people need to treat climate change “like the existential crisis it is.”

Thunberg was one of four students invited to a joint hearing of the House Foreign Affairs Subcommittee on Europe, Eurasia, Energy and the Environment and the Select Committee on the Climate Crisis, to provide the next generation’s views on climate change.

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Her first appearance took place last Friday in front of the White House, where she encouraged fellow young activists to keep fighting to be heard. She did not mention President Donald Trump, a climate change denier who moved to withdraw the United States from the Paris Climate Change Agreement early in his tenure, in her remarks.

On Wednesday, she called out the United States for being the “biggest carbon polluter in history” and the top producer of oil.

“And yet you are also the only nation in the world who has signaled with strong intention to leave the Paris agreement because it was a bad deal for the U.S.,” she said.

Trump earlier in the day announced plans to revoke California's ability here to set emissions standards for vehicles that are more stringent than the federal standards - the latest move in his administration’s multi-pronged attack on California's efforts to reduce vehicle emissions, which could slow the deployment of electric and more efficient vehicles.

A conservative climate-change advocate at Wednesday’s hearing, 21-year-old Benji Backer from Wisconsin, told lawmakers that young conservatives also favor climate change action, but through an approach focused on technology and allowing the continued use of fossil fuels.

“As a proud American, as a life-long conservative and as a young person, I urge you to accept climate change for the reality it is and respond accordingly. We need your leadership,” he said.

Backer praised Thunberg and other climate activists for putting the issue at the forefront of politics, but said there was time to take more measured action.

In addition to meetings on Capitol Hill, Thunberg met former President Barack Obama on Tuesday. Obama described the teenager on Twitter as “already one of the planet’s greatest advocates.”

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Though Thunberg mostly addressed admiring Democratic lawmakers, she also spoke to some Republican lawmakers at the House hearing.

Republican representatives praised the students for raising awareness about climate change but disagreed over what action the United States should take when emerging economies continue to emit greenhouse gases as their economies grow.

Representative Garret Graves from Louisiana said his state was affected by rising sea levels and that he supported the U.S. emission reduction target enshrined in the Paris Climate Agreement, but he criticized the pact for how it treats emerging economies like China.

“I think that signing on to an agreement...that allows for China to have a 50% increase in greenhouse gas emissions annually by 2030 is inappropriate,” he said.

Thunberg responded that in her home country, Sweden, people similarly criticize the United States for not taking enough action. “The same argument is being used against you,” she said.